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Costăchescu B, Niculescu AG, Grumezescu AM, Teleanu DM. Screw Osteointegration-Increasing Biomechanical Resistance to Pull-Out Effect. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5582. [PMID: 37629873 PMCID: PMC10456840 DOI: 10.3390/ma16165582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 08/03/2023] [Accepted: 08/09/2023] [Indexed: 08/27/2023]
Abstract
Spinal disorders cover a broad spectrum of pathologies and are among the most prevalent medical conditions. The management of these health issues was noted to be increasingly based on surgical interventions. Spinal fixation devices are often employed to improve surgery outcomes, increasing spinal stability, restoring structural integrity, and ensuring functionality. However, most of the currently used fixation tools are fabricated from materials with very different mechanical properties to native bone that are prone to pull-out effects or fail over time, requiring revision procedures. Solutions to these problems presently exploited in practice include the optimal selection of screw shape and size, modification of insertion trajectory, and utilization of bone cement to reinforce fixation constructs. Nevertheless, none of these methods are without risks and limitations. An alternative option to increasing biomechanical resistance to the pull-out effect is to tackle bone regenerative capacity and focus on screw osteointegration properties. Osteointegration was reportedly enhanced through various optimization strategies, including use of novel materials, surface modification techniques (e.g., application of coatings and topological optimization), and utilization of composites that allow synergistic effects between constituents. In this context, this paper takes a comprehensive path, starting with a brief presentation of spinal fixation devices, moving further to observations on how the pull-out strength can be enhanced with existing methods, and further focusing on techniques for implant osteointegration improvement.
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Affiliation(s)
- Bogdan Costăchescu
- “Gr. T. Popa” University of Medicine and Pharmacy, 700115 Iasi, Romania;
- “Prof. Dr. N. Oblu” Emergency Clinical Hospital, 700309 Iasi, Romania
| | - Adelina-Gabriela Niculescu
- Research Institute of the University of Bucharest—ICUB, University of Bucharest, 050657 Bucharest, Romania;
- Department of Science and Engineering of Oxide Materials and Nanomaterials, Politehnica University of Bucharest, 011061 Bucharest, Romania
| | - Alexandru Mihai Grumezescu
- Research Institute of the University of Bucharest—ICUB, University of Bucharest, 050657 Bucharest, Romania;
- Department of Science and Engineering of Oxide Materials and Nanomaterials, Politehnica University of Bucharest, 011061 Bucharest, Romania
- Academy of Romanian Scientists, Ilfov No. 3, 050044 Bucharest, Romania
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Wu J, Lin T, Jiang H, Ma J, Zhang K, Zhao J, Zhou X, Wang C. The treatment efficacy of cortical bone trajectory (CBT) pedicle screws for lumbar degenerative disease in the Chinese Han population. Front Surg 2022; 9:421815. [PMID: 36386519 PMCID: PMC9659752 DOI: 10.3389/fsurg.2022.421815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/15/2022] [Indexed: 11/05/2022] Open
Abstract
Purpose To provide reference data on CBT pedicle screws from CT measurements of L1 to L5 in the Chinese Han population and to assess the treatment efficacy of CBT pedicle screws in cases of lumbar degenerative disease. Methods In total, 100 patients were identified from the CT database for CBT morphometric measurement of the lumbar spine. According to sex and age, patients were divided into four groups. The diameter, length, and angle of the vertebral pedicle and trajectory were measured. Then, a total of 36 patients with lumbar degenerative disease were included in this study for clinical and radiographic evaluation. Demographic characteristics, health-related quality of life (HRQOL), and extent of intervertebral disc herniation and spondylolisthesis were evaluated. Results The mean diameter and the mean length varied from L1 to L5 in Groups I to IV. The lateral angles ranging from L1 to L5 were 8.9 to 9.2°, 8.7 to 12.2°, 8.7 to 11.2°, and 9.2 to 10.1° in Groups I to IV, respectively. The cephalad angles from L1 to L5 were 23.5 to 28.6°, 24.7 to 26.6°, 25.0 to 28.2°, and 24.7 to 27.9° in Groups I to IV, respectively. In the case series, all patients’ neurological function and HRQOL were significantly improved at the final follow-up (p < 0.0001), and 75% of patients achieved satisfaction. Conclusions The morphology of the lumbar vertebral pedicle varied from L1 to L5, and the trajectory was feasible and safe. CBT pedicle screws were effective in treating lumbar degenerative diseases and benefited the patients.
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Aycan MF, Arslan AK, Uslan Y, Demir T. Postfusion effect on pullout strength of pedicle screws with expandablepeek shell and conventional screws. Acta Orthop Belg 2022; 88:433-440. [PMID: 36791695 DOI: 10.52628/88.3.6855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The pullout performance of various pedicle screws after artificial fusion process was investigated in this study. Normal, cannulated (cemented), novel expandable and normal (cemented) pedicle screws were tested. Polyurethane foams (Grade 10 and Grade 40) produced by casting method were used as test materials. The instrumentation of pedicle screws has been carried out with production of foams, simultaneously. For cemented pedicle screws, 3D models were prepared with respect to the anteriosuperior and oblique radiographs by using PMMA before casting procedure. Pullout tests were performed in an Instron 3369 testing device. Load versus displacement graph was recorded and the ultimate force was defined as the pullout strength sustained before failure of screw. As expected, the pullout strengths of pedicle screws in postfusion are higher than before fusion. Pullout strengths increased significantly by artificial fusion in Grade 10 foams compared to Grade 40 foams. Additionally, while the pullout strengths of normal, cannulated and novel expandable pedicle screws increased by artificial fusion, cemented normal pedicle screws had lower pullout values than before fusion in Grade 40 foams. When the cemented normal pedicle screws are excluded, other screws have almost similar pullout strength level. On the other hand, the pedicle screws have different increasing behaviour also, there is no correlation between each other. As a result, the novel expandable pedicle screws can be used instead of normal and cannulated ones due to their performances in non-cemented usage.
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De Kater EP, Weststeijn CF, Sakes A, Breedveld P. A Toggling Resistant In-Pedicle Expandable Anchor: A Preliminary Study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:3313-3317. [PMID: 36086162 DOI: 10.1109/embc48229.2022.9871068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Loosening of pedicle screws after spinal fusion surgery can prevent the desired fusion between vertebrae and may be a reason for revision surgery. Especially in osteoporotic bone, toggling of pedicle screws is a common problem that compromises the fixation strength of these screws and can lead to loosening or axial pull-out of the screw. In this study, we explore the use of an in-pedicle expandable anchor that shapes to the pedicle to increase the toggling resistance of the anchor by increasing the contact area between the anchor and the dense cortical bone of the pedicle. A scaled-up, two-dimensional prototype was designed. The prototype consists of a bolt and ten stainless steel wedges that expand by tensioning the bolt. During the expansion, the wedges are required to compress the cancellous bone. Based on the first preliminary experiment, it was found that the expansion of the wedges resulted in successful compression of 5 PCF cancellous bone phantom (Sawbones). This preliminary study shows that an expandable in-pedicle anchor could be a feasible option to increase the toggling resistance of spinal bone anchors, especially in osteoporotic bone. Clinical Relevance- Toggling of pedicle screws is a major cause of screw loosening. In this preliminary study, the use of an in-pedicle expandable anchor to increase the toggling resistance of spinal bone anchors is explored.
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Beyond the pedicle screw-a patent review. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2022; 31:1553-1565. [PMID: 35380271 DOI: 10.1007/s00586-022-07193-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 03/17/2022] [Accepted: 03/18/2022] [Indexed: 10/18/2022]
Abstract
PURPOSE This review provides an overview of the patent literature on posteriorly placed intrapedicular bone anchors. Conventional pedicle screws are the gold standard to create a fixation in the vertebra for spinal fusion surgery but may lack fixation strength, especially in osteoporotic bone. The ageing population demands new bone anchors that have an increased fixation strength, that can be placed safely, and, if necessary, can be removed without damaging the surrounding tissue. METHODS The patent search was conducted using a classification search in the Espacenet patent database. Only patents with a Cooperative Patent Classification of A61B17/70 or A61B17/7001 concerning spinal positioners and stabilizers were eligible for inclusion. The search query resulted in the identification of 731 patents. Based on preset inclusion criteria, a total of 56 unique patents on different anchoring methods were included, reviewed and categorized in this study. RESULTS Five unique fixation methods were identified; (1) anchors that use threading, (2) anchors that utilize a curved path through the vertebra, (3) anchors that (partly) expand, (4) anchors that use cement and (5) anchors that are designed to initiate bone ingrowth. Of the anchor designs included in this study, eight had a corresponding commercial product, six of which were evaluated in clinical trials. CONCLUSION This review provides insights into worldwide patented intrapedicular bone anchors that aim to increase the fixation strength compared to the conventional pedicle screw. The identified anchoring methods and their working principles can be used for clinical decision-making and as a source of inspiration when designing novel bone anchors.
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Kanno H, Onoda Y, Hashimoto K, Aizawa T, Ozawa H. Innovation of Surgical Techniques for Screw Fixation in Patients with Osteoporotic Spine. J Clin Med 2022; 11:2577. [PMID: 35566703 PMCID: PMC9101243 DOI: 10.3390/jcm11092577] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/30/2022] [Accepted: 05/02/2022] [Indexed: 02/04/2023] Open
Abstract
Osteoporosis is a common disease in elderly populations and is a major public health problem worldwide. It is not uncommon for spine surgeons to perform spinal instrumented fusion surgeries for osteoporotic patients. However, in patients with severe osteoporosis, instrumented fusion may result in screw loosening, implant failure or nonunion because of a poor bone quality and decreased pedicle screw stability as well as increased graft subsidence risk. In addition, revision surgeries to correct failed instrumentation are becoming increasingly common in patients with osteoporosis. Therefore, techniques to enhance the fixation of pedicle screws are required in spinal surgeries for osteoporotic patients. To date, various instrumentation methods, such as a supplemental hook, sublaminar taping and sacral alar iliac screws, and modified screwing techniques have been available for reinforcing pedicle screw fixation. In addition, several materials, including polymethylmethacrylate and hydroxyapatite stick/granules, for insertion into prepared screw holes, can be used to enhance screw fixation. Many biomechanical tests support the effectiveness of these augmentation methods. We herein review the current therapeutic strategies for screw fixation and augmentation methods in the surgical treatment of patients with an osteoporotic spine.
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Affiliation(s)
- Haruo Kanno
- Department of Orthopaedic Surgery, Tohoku Medical and Pharmaceutical University, Sendai 983-8536, Japan;
- Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai 980-8574, Japan; (Y.O.); (K.H.); (T.A.)
| | - Yoshito Onoda
- Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai 980-8574, Japan; (Y.O.); (K.H.); (T.A.)
| | - Ko Hashimoto
- Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai 980-8574, Japan; (Y.O.); (K.H.); (T.A.)
| | - Toshimi Aizawa
- Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai 980-8574, Japan; (Y.O.); (K.H.); (T.A.)
| | - Hiroshi Ozawa
- Department of Orthopaedic Surgery, Tohoku Medical and Pharmaceutical University, Sendai 983-8536, Japan;
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Improved fixation stability for repairing pedicle screw loosening using a modified cement filling technique in porcine vertebrae. Sci Rep 2022; 12:2739. [PMID: 35177724 PMCID: PMC8854567 DOI: 10.1038/s41598-022-06724-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 02/04/2022] [Indexed: 01/20/2023] Open
Abstract
Polymethylmethacrylate (PMMA) has been applied clinically and biomechanically repair loose pedicle screws. Controversies have arisen over data due to uncontrolled cement properties, various locations and sizes of fenestrated holes in repair screws, irregular holes and different bone densities of specimens. In this study, the pullout strength was compared for two techniques, the modified technique to use PMMA to augment a threaded hole and the traditional technique with retrograde injection of a PMMA filling, for standard loose screws in porcine vertebrae. Both techniques provided statistically significant results for sufficiently randomized specimens and experimental procedures. The difference in the pullout strength between conical and cylindrical screws for the aforementioned cement augmentation techniques was also investigated. Twenty-four single-level fresh-frozen lumbar vertebrae from L1 to L6 were harvested from four mature pigs. A total of 0.8 ml of PMMA was retrograde injected into screw holes with a 5.5 mm diameter, followed by insertion of a 5.0 mm diameter repair screw in the traditional group (n = 12). A stiff threaded PMMA hole was created with a 4.5 mm tapping screw before insertion of repair screws in the modified group (n = 12). Two screw geometries were randomly assigned as cylindrical (n = 6) and conical (n = 6) in each group. The correlations between filling techniques, screw geometries and axial pullout strength were analyzed. An appropriate screw trajectory and insertion depth were confirmed using X-ray imaging prior to pullout testing in both groups. For a given screw geometry (cylindrical or conical), the pullout force of the modified group was significantly higher than that of the traditional group. There was no significant difference in the pullout force between the screw geometries for a given filling technique. The cement augmentation technique is far more influential than the screw outer geometry. The modified PMMA technique created a greater anchor force than the traditional method and could be an alternative for revision of pedicle screw loosening.
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Rosinski AA, Mittal A, Odeh K, Ungurean V, Leasure J, Telles C, Kondrashov D. Alternatives to Traditional Pedicle Screws for Posterior Fixation of the Degenerative Lumbar Spine. JBJS Rev 2021; 9:01874474-202107000-00016. [PMID: 34319968 DOI: 10.2106/jbjs.rvw.20.00177] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Traditional pedicle screws are currently the gold standard to achieve stable 3-column fixation of the degenerative lumbar spine. However, there are cases in which pedicle screw fixation may not be ideal. Due to their starting point lateral to the pars interarticularis, pedicle screws require a relatively wide dissection along with a medialized trajectory directed toward the centrally located neural elements and prevertebral vasculature. In addition, low bone mineral density remains a major risk factor for pedicle screw loosening, pullout, and pseudarthrosis. The purpose of this article is to review the indications, advantages, disadvantages, and complications associated with posterior fixation techniques of the degenerative lumbar spine beyond the traditional pedicle screws. METHODS Comprehensive literature searches of the PubMed, Scopus, and Web of Science databases were performed for 5 methods of posterior spinal fixation, including (1) cortical bone trajectory (CBT) screws, (2) transfacet screws, (3) translaminar screws, (4) spinous process plates, and (5) fusion mass screws and hooks. Articles that had been published between January 1, 1990, and January 1, 2020, were considered. Non-English-language articles and studies involving fixation of the cervical or thoracic spine were excluded from our review. RESULTS After reviewing over 1,700 articles pertaining to CBT and non-pedicular fixation techniques, a total of 284 articles met our inclusion criteria. CBT and transfacet screws require less-extensive exposure and paraspinal muscle dissection compared with traditional pedicle screws and may therefore reduce blood loss, postoperative pain, and length of hospital stay. In addition, several methods of non-pedicular fixation such as translaminar and fusion mass screws have trajectories that are directed away from or posterior to the spinal canal, potentially decreasing the risk of neurologic injury. CBT, transfacet, and fusion mass screws can also be used as salvage techniques when traditional pedicle screw constructs fail. CONCLUSIONS CBT and non-pedicular fixation may be preferred in certain lumbar degenerative cases, particularly among patients with osteoporosis. Limitations of non-pedicular techniques include their reliance on intact posterior elements and the lack of 3-column fixation of the spine. As a result, transfacet and translaminar screws are infrequently used as the primary method of fixation. CBT, transfacet, and translaminar screws are effective in augmenting interbody fixation and have been shown to significantly improve fusion rates and clinical outcomes compared with stand-alone anterior lumbar interbody fusion. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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Affiliation(s)
- Alexander A Rosinski
- San Francisco Orthopaedic Residency Program, St. Mary's Medical Center, San Francisco, California
| | - Ashish Mittal
- San Francisco Orthopaedic Residency Program, St. Mary's Medical Center, San Francisco, California
| | - Khalid Odeh
- San Francisco Orthopaedic Residency Program, St. Mary's Medical Center, San Francisco, California
| | | | | | | | - Dimitriy Kondrashov
- San Francisco Orthopaedic Residency Program, St. Mary's Medical Center, San Francisco, California
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Feng X, Qi W, Zhang T, Fang C, Liang H, Chen B, Leung F. Lateral migration resistance of screw is essential in evaluating bone screw stability of plate fixation. Sci Rep 2021; 11:12510. [PMID: 34131183 PMCID: PMC8206340 DOI: 10.1038/s41598-021-91952-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 05/31/2021] [Indexed: 11/09/2022] Open
Abstract
Conventional evaluation of the stability of bone screws focuses on pullout strength, while neglecting lateral migration resistance. We measured pullout strength and lateral migration resistance of bone screws and determined how these characteristics relate to screw stability of locking plate (LP) and dynamic compression plate (DCP) fixation. Pullout strength and lateral migration resistance of individual bone screws with buttress, square, and triangular thread designs were evaluated in polyurethane foam blocks. The screw types with superior performance in each of these characteristics were selected. LP and DCP fixations were constructed using the selected screws and tested under cyclic craniocaudal and torsional loadings. Subsequently, the association between individual screws’ biomechanical characteristics and fixation stability when applied to plates was established. Screws with triangular threads had superior pullout strength, while screws with square threads demonstrated the highest lateral migration resistance; they were selected for LP and DCP fixations. LPs with square-threaded screws required a larger force and more cycles to trigger the same amount of displacement under both craniocaudal and torsional loadings. Screws with triangular and square threads showed no difference in DCP fixation stability under craniocaudal loading. However, under torsional loading, DCP fixation with triangular-threaded screws demonstrated superior fixation stability. Lateral migration resistance is the primary contributor to locking screw fixation stability when applied to an LP in resisting both craniocaudal and torsional loading. For compression screws applied to a DCP, lateral migration resistance and pullout strength work together to resist craniocaudal loading, while pullout strength is the primary contributor to the ability to resist torsional loading.
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Affiliation(s)
- Xiaoreng Feng
- Department of Orthopaedics and Traumatology, Queen Mary Hospital, the University of Hong Kong, Pok Fu Lam, Hong Kong, SAR, China.,Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, China.,Yangjiang People's Hospital, Yangjiang, 529500, China
| | - Weichen Qi
- Department of Orthopaedics and Traumatology, Queen Mary Hospital, the University of Hong Kong, Pok Fu Lam, Hong Kong, SAR, China
| | - Teng Zhang
- Department of Orthopaedics and Traumatology, Queen Mary Hospital, the University of Hong Kong, Pok Fu Lam, Hong Kong, SAR, China
| | - Christian Fang
- Department of Orthopaedics and Traumatology, Queen Mary Hospital, the University of Hong Kong, Pok Fu Lam, Hong Kong, SAR, China
| | | | - Bin Chen
- Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, China.
| | - Frankie Leung
- Department of Orthopaedics and Traumatology, Queen Mary Hospital, the University of Hong Kong, Pok Fu Lam, Hong Kong, SAR, China.
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Abstract
AIMS To draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws. METHODS Buttress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared. RESULTS The barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure. CONCLUSION Bone screws with a reverse buttress thread design will significantly increase the pullout strength. Cite this article: Bone Joint Res 2021;10(2):105-112.
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Affiliation(s)
- Xiaoreng Feng
- Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Southern Medical University, Guangzhou, China.,Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.,Department of Orthopaedics & Traumatology, Yangjiang People's Hospital, Yangjiang, China
| | - Weichen Qi
- Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Christian X Fang
- Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - William W Lu
- Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Frankie K L Leung
- Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Bin Chen
- Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Southern Medical University, Guangzhou, China
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Gazzeri R, Panagiotopoulos K, Galarza M, Bolognini A, Callovini G. Minimally invasive spinal fixation in an aging population with osteoporosis: clinical and radiological outcomes and safety of expandable screws versus fenestrated screws augmented with polymethylmethacrylate. Neurosurg Focus 2020; 49:E14. [DOI: 10.3171/2020.5.focus20232] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 05/12/2020] [Indexed: 11/06/2022]
Abstract
OBJECTIVEThe goal of this study was to compare the clinical and radiological outcomes between fenestrated pedicle screws augmented with cement and expandable pedicle screws in percutaneous vertebral fixation surgical procedures for the treatment of degenerative and traumatic spinal diseases in aging patients with osteoporosis.METHODSThis was a prospective, single-center study. Twenty patients each in the expandable and cement-augmented screw groups were recruited. Clinical outcomes included visual analog scale (VAS), Oswestry Disability Index (ODI), and satisfaction rates. Radiographic outcomes comprised radiological measurements on the vertebral motion segment of the treated levels. Intraoperative data including complications were collected. All patients completed the clinical and radiological outcomes. Outcomes were compared preoperatively and postoperatively.RESULTSAn average shorter operative time was found in procedures in which expandable screws were used versus those in which cement-augmented screws were used (p < 0.001). No differences resulted in perioperative blood loss between the 2 groups. VAS and ODI scores were significantly improved in both groups after surgery. There was no significant difference between the 2 groups with respect to baseline VAS or ODI scores. The satisfaction rate of both groups was more than 85%. Radiographic outcomes also showed no significant difference in segment stability between the 2 groups. No major complications after surgery were seen. There were 4 cases (20%) of approach-related complications, all in fenestrated screw procedures in which asymptomatic cement extravasations were observed. In 1 case the authors detected a radiologically evident osteolysis around a cement-augmented screw 36 months after surgery. In another case they identified a minor loosening of an expandable screw causing local back discomfort at the 3-year follow-up.CONCLUSIONSExpandable pedicle screws and polymethylmethacrylate augmentation of fenestrated screws are both safe and effective techniques to increase the pullout strength of screws placed in osteoporotic spine. In this series, clinical and radiological outcomes were equivalent between the 2 groups. To the authors’ knowledge, this is the first report comparing the cement augmentation technique versus expandable screws in the treatment of aging patients with osteoporosis.
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Affiliation(s)
- Roberto Gazzeri
- 1Department of Neurosurgery, San Giovanni–Addolorata Hospital, Rome
- 2Department of Neurosurgery, IRCCS Istituto Nazionale Tumori “Regina Elena,” Rome, Italy; and
| | | | - Marcelo Galarza
- 3Regional Service of Neurosurgery, “Virgen de la Arrixaca” University Hospital, Murcia, Spain
| | - Andrea Bolognini
- 1Department of Neurosurgery, San Giovanni–Addolorata Hospital, Rome
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Use of longer sized screws is a salvage method for broken pedicles in osteoporotic vertebrae. Sci Rep 2020; 10:10441. [PMID: 32591573 PMCID: PMC7320151 DOI: 10.1038/s41598-020-67489-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 06/05/2020] [Indexed: 11/09/2022] Open
Abstract
Screw loosening due to broken pedicles is a common complication resulting from the insertion of screws either with inadequate diameters or into an osteoporotic pedicle. In this novel in vitro study, we tried to clarify the contribution of the pedicle to screw fixation and subsequent salvage strategies using longer or larger-diameter screws in broken pedicles. Sixty L4 fresh-frozen lumbar vertebrae harvested from mature pigs were designed as the normal-density group (n = 30) and decalcified as the osteoporosis group (n = 30). Three modalities were randomly assigned as intact pedicle (n = 30), semi-pedicle (n = 15), and non-pedicle (n = 15) in each group. Three sizes of polyaxial screws (diameter × length of 6.0 mm × 45 mm, 6.0 mm × 50 mm, and 6.5 mm × 45 mm) over five trials were used in each modality. The associations between bone density, pedicle modality and screw pullout strength were analyzed. After decalcification for 4 weeks, the area bone mineral density decreased to approximately 56% (p < 0.05) of the normal-density group, which was assigned as the osteoporosis group. An appropriate screw trajectory and insertional depth were confirmed using X-ray imaging prior to pullout testing in both groups. The pullout forces of larger-diameter screws (6.5 mm × 45 mm) and longer screws (6.0 mm × 50 mm) were significantly higher (p < 0.05) in the semi- and non-pedicle modalities in the normal-density group, whereas only longer screws (6.0 mm × 50 mm) had a significantly higher (p < 0.05) pullout force in the non-pedicle modalities in the osteoporosis group. The pedicle plays an important role in both the normal bone density group and the osteoporosis group, as revealed by analyzing the pullout force percentage contributed by the pedicle. Use of a longer screw would be a way to salvage a broken pedicle of osteoporotic vertebra.
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14
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Varghese V, Krishnan V, Kumar GS. Comparison of pullout strength of pedicle screws following revision using larger diameter screws. Med Eng Phys 2019; 74:180-185. [DOI: 10.1016/j.medengphy.2019.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 08/06/2019] [Accepted: 09/08/2019] [Indexed: 02/03/2023]
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15
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Kanno H, Aizawa T, Hashimoto K, Itoi E. Enhancing percutaneous pedicle screw fixation with hydroxyapatite granules: A biomechanical study using an osteoporotic bone model. PLoS One 2019; 14:e0223106. [PMID: 31557234 PMCID: PMC6762086 DOI: 10.1371/journal.pone.0223106] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 09/13/2019] [Indexed: 11/18/2022] Open
Abstract
Introduction Percutaneous pedicle screw (PPS) can provide internal fixation of the thoracolumbar spine through a minimally invasive surgical procedure. PPS fixation has been widely used to treat various spinal diseases. Rigid fixation of PPS is essential for managing osteoporotic spine in order to prevent the risks of screw loosening and implant failure. We recently developed a novel augmentation method using hydroxyapatite (HA) granules for PPS fixation. The aim of this study was to evaluate the strength and stiffness of PPS fixation augmented with HA granules using an osteoporotic bone model. Methods Screws were inserted into uniform synthetic bone (sawbones) with and without augmentation. The uniaxial pullout strength and insertion torque of the screws were evaluated. In addition, each screw underwent cyclic toggling under incrementally increasing physiological loads until 2 mm of screwhead displacement occurred. The maximal pullout strength (N), maximal insertion torque (N·cm), number of toggle cycles and maximal load (N) required to achieve 2-mm screwhead displacement were compared between the screws with and without augmentation. Results The maximal pullout strength was significantly stronger for screws with augmentation than for those without augmentation (302 ± 19 N vs. 254 ± 17 N, p < 0.05). In addition, the maximal insertion torque was significantly increased in screws with augmentation compared to those without augmentation (48 ± 4 N·cm vs. 26 ± 5 N·cm, p < 0.05). Furthermore, the number of toggle cycles and the maximal load required to reach 2 mm of displacement were significantly greater in screws with augmentation than in those without augmentation (106 ± 9 vs. 52 ± 10 cycles; 152 ± 4 N vs. 124 ± 5 N, p < 0.05). Conclusions Augmentation using HA granules significantly enhanced the rigidity of PPS fixation in the osteoporotic bone model. The present study suggested that novel augmentation with HA granules may be a useful technique for PPS fixation in patients with osteoporotic spine.
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Affiliation(s)
- Haruo Kanno
- Department of Orthopedic Surgery, Tohoku University School of Medicine, Sendai, Japan
- * E-mail:
| | - Toshimi Aizawa
- Department of Orthopedic Surgery, Tohoku University School of Medicine, Sendai, Japan
| | - Ko Hashimoto
- Department of Orthopedic Surgery, Tohoku University School of Medicine, Sendai, Japan
| | - Eiji Itoi
- Department of Orthopedic Surgery, Tohoku University School of Medicine, Sendai, Japan
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Hsieh MK, Liu MY, Chen JK, Tsai TT, Lai PL, Niu CC, Tai CL. Biomechanical study of the fixation stability of broken pedicle screws and subsequent strategies. PLoS One 2019; 14:e0219189. [PMID: 31251780 PMCID: PMC6599116 DOI: 10.1371/journal.pone.0219189] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Accepted: 06/18/2019] [Indexed: 11/18/2022] Open
Abstract
Pedicles are often broken when screws are inserted into hard pedicles with small diameters or when the diameter of the screw itself is inadequate. However, there is a lack of biomechanical literature that addresses screw loosening as a result of broken pedicles or the resulting salvage of those screws. We performed a novel in vitro study to compare the pullout strength of screws between intact pedicles and two different types of broken pedicles; strategies to prevent screw loosening were also compared. Thirty L4 Sawbones were designed to represent intact pedicles, semi-pedicles, and nonpedicles and were prepared for screw insertion. Three sizes of polyaxial screws (diameter × length dimensions of 6.0 mm × 45 mm, 6.0 mm × 50 mm and 6.5 mm × 45 mm) were independently and randomly distributed into the intact-pedicle group (IP group, n = 30), the semi-pedicle group (SP group, n = 15), or the nonpedicle group (NP group, n = 15). The experiments were conducted across a minimum of five trials for each of the chosen screw sizes. We then analyzed the results of the imaging, pullout testing, and embedded bone volume. Any fractures or defects of the vertebrae caused by screw insertion were excluded from the study. The appropriate screw trajectory and insertional depth were confirmed using axial and sagittal X-ray imaging prior to screw pullout testing. A pullout strength of only 41% to 45% for the SP group and 29% to 39% for the NP group was retained following a broken pedicle. The use of longer or larger-diameter screws appears to be an effective salvaging procedure for the NP group (p < 0.05). The embedded bone volume percentage analysis indicated that, compared to the IP group, 68% to 76% of effective bone embedded into the screw threads in the SP group, and 58% to 65% in the NP group. There was no direct correlation between the pullout strength and the embedded bone volume; however, less effective embedded bone volume was associated with lower pullout strength. This study describes the evolution of the well-established screw pullout test being applied to the broken pedicle Sawbone testing model. The pedicle plays an important role in determining the pullout strength of a screw. However, a salvage procedure that utilizes a longer or larger-diameter screw might be a reliable clinical approach to address broken pedicles.
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Affiliation(s)
- Ming-Kai Hsieh
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Mu-Yi Liu
- Ph.D. Program in Biomedical Engineering, Collage of Engineering, Chang Gung University, Taoyuan, Taiwan
| | - Jin-Kai Chen
- Graduate Institute of Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan
| | - Tsung-Ting Tsai
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Po-Liang Lai
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Chi-Chien Niu
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Ching-Lung Tai
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan
- * E-mail:
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17
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Choy WJ, Walsh WR, Phan K, Mobbs RJ. Technical Note: Pedicle Cement Augmentation with Proximal Screw Toggle and Loosening. Orthop Surg 2019; 11:510-515. [PMID: 31179643 PMCID: PMC6595100 DOI: 10.1111/os.12467] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 04/05/2019] [Accepted: 04/05/2019] [Indexed: 12/26/2022] Open
Abstract
Background Cement augmentation is a technique used to increase the stability and purchase of pedicle screws in poor quality bone. Various methods can be applied for cement delivery, such as cement injection before screw placement and the use of fenestrated screws. However, potential problems can arise with the use of cement augmentation. Case Presentation A 66‐year‐old man with a lower trunk deformity, severe kyphosis, and sagittal imbalance following fusion (L2‐5), with minimal comorbidities, was referred to our unit 9 months after surgery. Pain and progressive kyphosis were investigated clinically and radiographically with computed tomography (CT) scans to assess the status of the hardware and fusion. CT imaging revealed that cement was present only at the distal tip of the fenestrated screws at the L4 vertebral level. A non‐union was present along with loosening and a halo around the body of the pedicle screws, and there was evidence of pullout of inferior screws. Conclusion Single‐level cement augmentation of pedicle screw in a posterior construct and distal tip cement augmentation of the screw results in a fixed pivot point. Micromotion in cranio‐caudal loading during flexion and extension may result in screw toggling with the single‐level cement‐augmented tip as a fulcrum. This may cause screw loosening, which can lead to pullout and loss of construct stability. The halo around the screw suggests bone loss and/or a fibrous tissue interface, which further complicates revision surgery. Stress shielding and polymethylmethacrylate cement present additional difficulties. The findings of this technical note question the risks and benefits of cement‐augmented fenestrated pedicle screw fixation for spinal fusion. Although incidences of such cases are uncommon, surgeons should perform this technique with caution. Accurate restoration of lumbar lordosis during index procedures is important to minimize the risk of construct failure.
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Affiliation(s)
- Wen Jie Choy
- NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia.,Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - William R Walsh
- Surgical & Orthopaedic Research Laboratory, Prince of Wales Clinical School, University of New South Wales, Sydney, Randwick, New South Wales, Australia
| | - Kevin Phan
- NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia.,Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.,Prince of Wales Private Hospital, New South Wales, Australia
| | - Ralph J Mobbs
- NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia.,Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.,Prince of Wales Private Hospital, New South Wales, Australia
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18
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Bohl MA, Morgan CD, Mooney MA, Repp GJ, Lehrman JN, Kelly BP, Chang SW, Turner JD, Kakarla UK. Biomechanical Testing of a 3D-printed L5 Vertebral Body Model. Cureus 2019; 11:e3893. [PMID: 30911450 PMCID: PMC6424546 DOI: 10.7759/cureus.3893] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Background We examined the biomechanical performance of a three-dimensional (3D)-printed vertebra on pedicle screw insertional torque (IT), axial pullout (APO), and stiffness (ST) testing. Materials and methods Seventy-three anatomically identical L5 vertebral body models (146 pedicles) were printed and tested for IT, APO, and ST using single-threaded pedicle screws of equivalent diameter (6.5 mm), length (40.0 mm), and thread pitch (2.6 mm). Print properties (material, cortical thickness [number of shells], cancellous density [in-fill], in-fill pattern, print orientation) varied among models. One-way analysis of variance was performed to evaluate the effects of variables on outcomes. Results The type of material significantly affected IT, APO, and ST (P < 0.001, all comparisons). For acrylonitrile butadiene styrene (ABS) models, in-fill density (25-35%) had a positive linear association with APO (P = 0.002), ST (P = 0.008), and IT (P = 0.10); similarly for the polylactic acid (PLA) models, APO (P = 0.001), IT (P < 0.001), and ST (P = 0.14). For the nylon material type, in-fill density did not affect any tested parameter. For a given in-fill density, material, and print orientation, the in-fill pattern significantly affected IT (P = 0.002) and APO (P = 0.03) but not ST (P = 0.23). Print orientation also significantly affected IT (P < 0.001), APO (P < 0.001), and ST (P = 0.002). Conclusions 3D-printed vertebral body models with specific print parameters can be designed to perform analogously to human bone on pedicle screw tests of IT, APO, and ST. Altering the material, in-fill density, in-fill pattern, and print orientation of synthetic vertebral body models could reliably produce a model that mimics bone of a specific bone mineral density.
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Affiliation(s)
- Michael A Bohl
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Clinton D Morgan
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Michael A Mooney
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Garrett J Repp
- Department of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Steve W Chang
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - U Kumar Kakarla
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
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19
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Superior cortical screw in osteoporotic lumbar vertebrae: A biomechanics and microstructure-based study. Clin Biomech (Bristol, Avon) 2018; 53:14-21. [PMID: 29407351 DOI: 10.1016/j.clinbiomech.2018.01.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 12/11/2017] [Accepted: 01/21/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND Osteoporosis reduces the bone-screw purchase, potentially reducing pullout strength and other biomechanical properties. However, the existing pedicle screw approach may not compensate for the detrimental effects of decreased vertebral bone mineral density. METHODS Two methods of screw insertion were performed in thirteen cadaveric osteoporotic lumbar vertebrae: Magerl's method in the left pedicle, and superior cortical screw method in the right (its entry point located vertically 3 mm above Magerl's point). Before screw fixations, the pedicle and its corresponding vertebral body were divided into six equal layers from cranial to caudal by performing micro-CT and tested for microstructure properties, such as bone mineral density, trabecular bone volume fraction, trabecular thickness, trabecular separation and trabecular number. Further, pedicle was horizontally divided into three regions and tested. After screw fixations, microstructure properties of the bone surrounding the screws were analyzed. Finally, the screw pullout strength was tested biomechanically. FINDINGS The bone structure is denser in the upper third of the pedicle and its corresponding vertebral body. A similar microstructure is seen within the pedicle. This study reveals that the pullout strength is significantly correlated to the bone mineral density, trabecular bone volume fraction and trabecular thickness. Biomechanical test showed pullout strength in the superior cortical screw group with mean 613.3 N (SD 200.4) was 22.4% higher than that in the Magerl group with mean 501.2 N (SD 256.6). INTERPRETATION The superior cortical screw method can be a reliable alternative, to provide better pullout strength for posterior lumbar instrumentation, especially in osteoporotic patients.
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20
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Aycan MF, Yaman ME, Usta Y, Demir T, Tolunay T. Investigation of toggling effect on pullout performance of pedicle screws. Proc Inst Mech Eng H 2018; 232:395-402. [DOI: 10.1177/0954411918755417] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Objective of this study is to assess the pullout performance of various pedicle screws in different test materials after toggling tests comparatively. Solid core, cannulated (cemented), novel expandable and solid-core (cemented) pedicle screws were instrumented to the polyurethane foams (Grade 10 and Grade 40) produced in laboratory and bovine vertebra. ASTM F543 standard was used for preparation process of samples. Toggling tests were carried out. After toggling test procedures, pullout tests were performed. Load versus displacement graph was recorded, and the ultimate pullout force was defined as the maximum load (pullout strength) sustained before failure of screw. Anteriosuperior and oblique radiographs were taken from each sample after instrumentation in order to examine screw placement and cement distribution. The pullout strength of pedicle screws decreased after toggling tests with respect to the initial condition. While the cemented solid-core pedicle screws had the highest pullout strength in all test materials, they had the highest strength differences. The cemented solid-core pedicle screws had decrement rates of 27% and 16% in Grade 10 and Grade 40, respectively. There are almost same decrement rate (between 5.5% and 6.5%) for all types of pedicle screws instrumented to the samples of bovine vertebra. The pullout strengths of novel expandable pedicle screws in both of early period and after toggling conditions were almost similar, in other words, the decrement rates of it were lower than other types. According to the data collected from this study, polymethylmethacrylate augmentation significantly decreases pullout strength following the toggling loads. Higher brittleness of cured polymethylmethacrylate has adverse effect on the pullout strength. Although augmentation is an important process for enhancing pullout strength in early period, it has some disadvantages for preserving stabilization in a long time. Expandable pedicle screw with polyetheretherketone shell may be good alternative to polymethylmethacrylate augmentation on both primer stabilization and long-term loading application with toggling.
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Affiliation(s)
| | - Mesut Emre Yaman
- Department of Neurosurgery, Memorial Ankara Hospital, Ankara, Turkey
| | - Yusuf Usta
- Department of Mechanical Engineering, Gazi University, Ankara, Turkey
| | - Teyfik Demir
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
| | - Tolga Tolunay
- Department of Orthopedics, Yıldırım Beyazıt University, Ankara, Turkey
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21
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Palepu V, Helgeson MD, Molyneaux-Francis M, Nagaraja S. Impact of bone quality on the performance of integrated fixation cage screws. Spine J 2018; 18:321-329. [PMID: 28823940 DOI: 10.1016/j.spinee.2017.08.239] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 06/29/2017] [Accepted: 08/09/2017] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Commercially available lumbar integrated fixation cages (IFCs) have variable designs. For example, screw-based designs have up to four screws inserted at different locations across the vertebral end plate as well as at different angles in the sagittal and transverse planes. This is important as end plate and trabecular bone quality may vary across the vertebra and may affect the screw's fixation ability, particularly if bone purchase at the bone-screw interface is poor. PURPOSE This study aimed to evaluate whether variations in local bone quality surrounding IFC screws inserted at different locations in the vertebrae would affect their mechanical performance. STUDY DESIGN This study is an in vitro human cadaveric biomechanical analysis. MATERIALS AND METHODS Fourteen lumbar (L3 and L4) vertebrae from 10 cadavers (age: 76±10 years, bone mineral density: 0.89±0.17 g/cm2) were used for this study. Pilot holes (3.5-mm diameter×15-mm length) representing three different IFC screw orientations (lateral to medial [LM], midsagittal [MS], and medial to lateral [ML]) were created in vertebrae using an IFC guide and bone awl. The screw locations and trajectories chosen are representative of commercially available IFC designs. These pilot holes were then imaged with high-resolution microcomputed tomography to obtain a three-dimensional structure of the bone surrounding the pilot hole. Local bone morphology was then quantified by evaluating a 3-mm-thick circumferential volume surrounding the pilot hole. Integrated fixation screws were implanted into pilot holes while recording maximum screw insertional torques. Screws were toggled in the cranial direction from 10 to 50 N for first 10,000 cycles, and the maximum load was increased by 25 N for every 5,000 cycles for a total of 25,000 cycles. RESULTS Total bone volume (BV) and trabecular bone volume fraction surrounding ML screws were significantly greater (p<.03) compared with those around MS screws and LM screws. The maximum insertional torque for ML screws were greater (p=.06) than LM and significantly greater (p<.02) than MS screws. The number of cycles to failure for the ML screw was significantly greater (p<.04) than that for the LM and the MS screws. Total BV (R2≤46.2%, p<.03) and the maximum insertional torque (R2≤59.6%, p<.03) provided better correlations to screw loosening compared with all the other bone quality parameters. CONCLUSIONS Our findings indicate that bone quality in the vertebral body varied spatially depending on the orientation and the insertion location of the IFC screw. These alterations in local bone quality significantly affected the screw's ability to fixate to bone. These variations in bone quality may be assessed intraoperatively using screw insertional torque measurements. By understanding available bone purchase at the bone-implant interface, the appropriate implant design can be selected to maximize the fixation strength.
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Affiliation(s)
- Vivek Palepu
- Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Applied Mechanics, U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Melvin D Helgeson
- Department of Orthopaedics, Walter Reed National Military Medical Center, 4494 North Palmer Rd, Bethesda, MD 20889, USA
| | - Michael Molyneaux-Francis
- Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Applied Mechanics, U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Srinidhi Nagaraja
- Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Applied Mechanics, U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA.
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Martín-Fernández M, López-Herradón A, Piñera AR, Tomé-Bermejo F, Duart JM, Vlad MD, Rodríguez-Arguisjuela MG, Alvarez-Galovich L. Potential risks of using cement-augmented screws for spinal fusion in patients with low bone quality. Spine J 2017; 17:1192-1199. [PMID: 28606606 DOI: 10.1016/j.spinee.2017.04.029] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 03/20/2017] [Accepted: 04/24/2017] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Dramatic increases in the average life expectancy have led to increases in the variety of degenerative changes and deformities observed in the aging spine. The elderly population can present challenges for spine surgeons, not only because of increased comorbidities, but also because of the quality of their bones. Pedicle screws are the implants used most commonly in spinal surgery for fixation, but their efficacy depends directly on bone quality. Although polymethyl methacrylate (PMMA)-augmented screws represent an alternative for patients with osteoporotic vertebrae, their use has raised some concerns because of the possible association between cement leakages (CLs) and other morbidities. PURPOSE To analyze potential complications related to the use of cement-augmented screws for spinal fusion and to investigate the effectiveness of using these screws in the treatment of patients with low bone quality. STUDY DESIGN A retrospective single-center study. PATIENT SAMPLE This study included 313 consecutive patients who underwent spinal fusion using a total of 1,780 cement-augmented screws. METHODS AND OUTCOME MEASURES We analyzed potential complications related to the use of cement-augmented screws, including CL, vascular injury, infection, screw extraction problems, revision surgery, and instrument failure. There are no financial conflicts of interest to report. RESULTS A total of 1,043 vertebrae were instrumented. Cement leakage was observed in 650 vertebrae (62.3%). There were no major clinical complications related to CL, but two patients (0.6%) had radicular pain related to CL at the S1 foramina. Of the 13 patients (4.1%) who developed deep infections requiring surgical debridement, two with chronic infections had possible spondylitis that required instrument removal. All patients responded well to antibiotic therapy. Revision surgery was performed in 56 patients (17.9%), most of whom had long construction. A total of 180 screws were removed as a result of revision. There were no problems with screw extraction. CONCLUSIONS These results demonstrate the efficacy and safety of cement-augmented screws for the treatment of patients with low bone mineral density.
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Affiliation(s)
- M Martín-Fernández
- Spine Department, Hospital Universitario Fundación Jiménez Díaz-UAM, Madrid, Spain
| | - A López-Herradón
- Spine Department, Hospital Universitario Fundación Jiménez Díaz-UAM, Madrid, Spain
| | - A R Piñera
- Spine Department, Hospital Universitario Fundación Jiménez Díaz-UAM, Madrid, Spain
| | - F Tomé-Bermejo
- Spine Department, Hospital Universitario Fundación Jiménez Díaz-UAM, Madrid, Spain
| | - J M Duart
- Spine Department, Hospital Universitario Fundación Jiménez Díaz-UAM, Madrid, Spain
| | - M D Vlad
- Faculty of Medical Bioengineering, "Gr. T. Popa" University of Medicine and Pharmacy, Iasi, Romania
| | | | - L Alvarez-Galovich
- Spine Department, Hospital Universitario Fundación Jiménez Díaz-UAM, Madrid, Spain.
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23
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Biomechanical Investigation of a Novel Revision Device in an Osteoporotic Model: Pullout Strength of Pedicle Screw Anchor Versus Larger Screw Diameter. Clin Spine Surg 2017. [PMID: 28632549 DOI: 10.1097/bsd.0000000000000313] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
STUDY DESIGN In vitro cadaveric biomechanical study. OBJECTIVE To assess revision pullout strength of novel anchored screws (AS) versus conventional larger diameter traditional pedicle screws (TPS) in an osteoporotic model. SUMMARY OF BACKGROUND DATA Pedicle screws are the most ubiquitous method of treating spinal pathologies requiring lumbar fusion. Although these screws are effective in providing 3-column stabilization of the spine, revision surgeries are occasionally necessary, particularly for geriatric and osteoporotic populations. Innovative technologies should be tested to ensure continued improvement in revision techniques. METHODS For 4 specimens at L2-L5 (T-score=-3.6±0.54), 6.5-mm-diameter TPS were inserted into left and right pedicles and were pulled out; revision screws were then inserted. Polyether-ether-ketone anchors, designed to expand around a 6.5-mm screw, were inserted into all left pedicles. On the contralateral side, 7.5-mm-diameter TPS were inserted at L2-L3, and 8.5-mm-diameter TPS at L4-L5. Pullout testing was performed at 10 mm/min. The maximum pullout strength and insertion forces were recorded. RESULTS The initial average pullout force (6.5-mm screw) was 837 N (±329 N) and 642 N (±318 N) in L2-L3 and L4-L5 left pedicles, and 705 N (±451 N) and 779 N (±378 N) in L2-L3 and L4-L5 right pedicles, respectively. Comparison of revision pullout forces versus initial pullout forces revealed the following: 87% and 63% for AS in L2-L3 and L4-L5 left pedicles, respectively; 56% for 7.5-mm and 93% for 8.5-mm TPS in L2-L3 and L4-L5 right pedicles, respectively. CONCLUSIONS Anchor sleeves with 6.5-mm-diameter pedicle screws provided markedly higher resistance to screw pullout than 7.5-mm-diameter revision screws and fixation statistically equivalent to 8.5-mm-diameter screws, possibly because of medial-lateral expansion within the vertebral space and/or convex filling of the pedicle. AS results had the lowest SD, indicating minimal variability in bone-screw purchase.
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24
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Pelletier MH, Bertollo N, Al-Khawaja D, Walsh WR. The contribution of the cortical shell to pedicle screw fixation. JOURNAL OF SPINE SURGERY 2017; 3:184-192. [PMID: 28744499 DOI: 10.21037/jss.2017.06.07] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND A pedicle screw insertion technique known as "hubbing" involves the removal of cortical bone around the screw insertion with the aim of improving fixation and decreasing screw loosening. However, the efficacy of this procedure relative to bone density and early loading have not been fully explored. The purpose of this study is to establish the contribution of the cortical layer (hubbing), cancellous density, early loading (toggling) in an idealised model. This is an in vitro laboratory study. METHODS Synthetic bone blocks with cancellous bulk and a simulated cortical shell were implanted with 6.5 mm pedicle screws. Three key variables were evaluated in this study; density of the simulated bone (10-20 lb/ft3), toggling (±0.5 mm for 10,000 cycles), and the presence or absence of the surrounding cortex (hubbing). Pullout testing after toggling was performed to determine maximum load, stiffness and energy. Results were analyzed to assess interaction and main effects. RESULTS Removal of the cortex decreased the pullout loads by approximately 1,100 N after toggling. Toggling in the presence of the cortical shell had no effect. However, once the cortical shell is removed damage to the weaker cancellous bone accumulates and further compromises the fixation. CONCLUSIONS The addition of a cortical layer in the Sawbone model is significant and provides a more realistic model of load sharing. The cortex plays a considerable role in the protection of underlying cancellous bone as well as contributing to initial pullout strength. The results of this study demonstrate a negative synergistic effect when both toggling and hubbing are applied to the weaker bone.
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Affiliation(s)
- Matthew Henry Pelletier
- Surgical & Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW Australia, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Nicky Bertollo
- Surgical & Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW Australia, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Darweesh Al-Khawaja
- Department of Neurosurgery, Wollongong Hospital, Wollongong, New South Wales 2500, Australia
| | - William Robert Walsh
- Surgical & Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW Australia, Prince of Wales Hospital, Sydney, NSW 2031, Australia
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Lorenz A, Leichtle CI, Frantz S, Bumann M, Tsiflikas I, Shiozawa T, Leichtle UG. Pull out Strength of Dual Outer Diameter Pedicle Screws Compared to Uncemented and Cemented Standard Pedicle Screws: A Biomechanical in vitro Study. Orthop Surg 2017; 9:229-236. [PMID: 28547867 DOI: 10.1111/os.12322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 01/26/2017] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVE To analyze the potential of the dual outer diameter screw and systematically evaluate the pull-out force of the dual outer diameter screw compared to the uncemented and cemented standard pedicle screws with special regard to the pedicle diameter and the vertebra level. METHODS Sixty vertebrae of five human spines (T 6 -L 5 ) were sorted into three study groups for pairwise comparison of the uncemented dual outer diameter screw, the uncemented standard screw, and the cemented standard screw, and randomized with respect to bone mineral density (BMD) and vertebra level. The vertebrae were instrumented, insertion torque was determined, and pull-out testing was performed using a material testing machine. Failure load was evaluated in pairwise comparison within each study group. The screw-to-pedicle diameter ratio was determined and the uncemented dual outer diameter and standard screws were compared for different ratios as well as vertebra levels. RESULTS Significantly increased pull-out forces were measured for the cemented standard screw compared to the uncemented standard screw (+689 N, P < 0.001) and the dual outer diameter screw (+403 N, P < 0.001). Comparing the dual outer diameter screw to the uncemented standard screw in the total study group, a distinct but not significant increase was measured (+149 N, P = 0.114). Further analysis of these two screws, however, revealed a significant increase of pull-out force for the dual outer diameter screw in the lumbar region (+247 N, P = 0.040), as well as for a screw-to-pedicle diameter ratio between 0.6 and 1 (+ 488 N, P = 0.028). CONCLUSIONS For clinical application, cement augmentation remains the gold standard for increasing screw stability. According to our results, the use of a dual outer diameter screw is an interesting option to increase screw stability in the lumbar region without cement augmentation. For the thoracic region, however, the screw-to-pedicle diameter should be checked and attention should be paid to screw cut out, if the dual outer diameter screw is considered.
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Affiliation(s)
- Andrea Lorenz
- Department of Orthopaedic Surgery, University Hospital Tübingen, Tübingen, Germany
| | - Carmen I Leichtle
- Department of Orthopaedic Surgery, University Hospital Tübingen, Tübingen, Germany.,Spine and Orthopaedic Surgery, Rottenburg, Germany
| | - Sandra Frantz
- Department of Orthopaedic Surgery, University Hospital Tübingen, Tübingen, Germany
| | - Marte Bumann
- Department of Orthopaedic Surgery, University Hospital Tübingen, Tübingen, Germany
| | - Ilias Tsiflikas
- Department of Radiology, University Hospital Tübingen, Tübingen, Germany
| | - Thomas Shiozawa
- Department of Clinical Anatomy and Cell Analytics, Institute of Anatomy, University of Tübingen, Tübingen, Germany
| | - Ulf G Leichtle
- Department of Orthopaedic Surgery, University Hospital Tübingen, Tübingen, Germany
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Aycan MF, Tolunay T, Demir T, Yaman ME, Usta Y. Pullout performance comparison of novel expandable pedicle screw with expandable poly-ether-ether-ketone shells and cement-augmented pedicle screws. Proc Inst Mech Eng H 2017; 231:169-175. [PMID: 28095741 DOI: 10.1177/0954411916687792] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Aim of this study is to assess the pullout performance of various pedicle screws in different test materials. Polyurethane foams (Grade 10 and Grade 40) produced in laboratory and bovine vertebrae were instrumented with normal, cannulated (cemented), novel expandable and normal (cemented) pedicle screws. Test samples were prepared according to the ASTM F543 standard testing protocols and surgical guidelines. To examine the screw placement and cement distribution, anteriosuperior and oblique radiographs were taken from each sample after insertion process was completed. Pullout tests were performed in an Instron 3369 testing device. Load versus displacement graphs were recorded and the ultimate pullout force was defined as the maximum load (pullout strength) sustained before failure of screw. Student's t-test was performed on each group whether the differences between pullout strength of pedicle screws were significant or not. While normal pedicle screws have the lowest pullout strength in all test materials, normal pedicle screws cemented with polymethylmethacrylate exhibit significantly higher pullout performance than others. For all test materials, there is a significant improvement in pullout strength of normal screws by augmentation. While novel expandable pedicle screws with expandable poly-ether-ether-ketone shells exhibited lower pullout performance than normal screws cemented with polymethylmethacrylate, their pullout performances in all groups were higher than the ones of normal and cannulated pedicle screws. For all test materials, although cannulated pedicle screws exhibit higher pullout strength than normal pedicle screws, there are no significant differences between the two groups. The novel expandable pedicle screws with expandable poly-ether-ether-ketone shells may be used instead of normal and cannulated pedicle screws cemented with polymethylmethacrylate due to their good performances.
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Affiliation(s)
| | - Tolga Tolunay
- 2 Department of Orthopaedics, Ankara Yildirim Beyazit University, Ankara, Turkey
| | - Teyfik Demir
- 3 Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
| | - Mesut Emre Yaman
- 4 Department of Neurosurgery, Memorial Ankara Hospital, Ankara, Turkey
| | - Yusuf Usta
- 1 Department of Mechanical Engineering, Gazi University, Ankara, Turkey
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Barbagallo GMV, Raudino G, Visocchi M, Alobaid AA, Al-Mutair AA, Naveen T, Certo F. Restoration of Thoracolumbar Spine Stability and Alignment in Elderly Patients Using Minimally Invasive Spine Surgery (MISS). A Safe and Feasible Option in Degenerative and Traumatic Spine Diseases. ACTA NEUROCHIRURGICA SUPPLEMENT 2017; 124:69-74. [DOI: 10.1007/978-3-319-39546-3_11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Effect of various factors on pull out strength of pedicle screw in normal and osteoporotic cancellous bone models. Med Eng Phys 2016; 40:28-38. [PMID: 27939099 DOI: 10.1016/j.medengphy.2016.11.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Revised: 11/21/2016] [Accepted: 11/27/2016] [Indexed: 12/27/2022]
Abstract
Pedicle screws are widely used for the treatment of spinal instability by spine fusion. Screw loosening is a major problem of spine fusion, contributing to delayed patient recovery. The present study aimed to understand the factor and interaction effects of density, insertion depth and insertion angle on pedicle screw pull out strength and insertion torque. A pull out study was carried out on rigid polyurethane foam blocks representing osteoporotic to normal bone densities according to the ASTM-1839 standard. It was found that density contributes most to pullout strength and insertion torque. The interaction effect is significant (p < 0.05) and contributes 8% to pull out strength. Axial pullout strength was 34% lower than angled pull out strength in the osteoporotic bone model. Insertion angle had no significant effect (p > 0.05) on insertion torque. Pullout strength and insertion torque had no significant correlation (p > 0.05) in the case of the extremely osteoporotic bone model.
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Gazzeri R, Roperto R, Fiore C. Surgical treatment of degenerative and traumatic spinal diseases with expandable screws in patients with osteoporosis: 2-year follow-up clinical study. J Neurosurg Spine 2016; 25:610-619. [PMID: 27314551 DOI: 10.3171/2016.3.spine151294] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Pedicle screw instrumentation of the osteoporotic spine carries an increased risk of screw loosening, pullout, and fixation failure. A variety of techniques have been used clinically to improve pedicle screw fixation in the presence of compromised bone. Pedicle screws may be augmented with cement, but this may lead to cement leakage and result in disastrous consequences. To avoid these complications, a multiaxial expandable pedicle screw has been developed. This was a prospective, single-center study designed to evaluate the clinical results of patients with osteoporosis with traumatic and degenerative spinal diseases treated with expandable pedicle screws. METHODS Thirty-three patients (mean age 61.4 years) with osteoporosis and traumatic or degenerative spinal diseases underwent spinal posterior fixation with expandable screws. Preoperative and postoperative visual analog scale (VAS) for pain and Oswestry Disability Index (ODI) questionnaire scores were obtained. The immediate postoperative screw position was measured and compared with the final position on lateral plain radiographs and axial CT scans at the 1- and 2-year follow-up examinations. RESULTS A total of 182 pedicle screws were used, including 174 expandable and 8 regular screws. The mean preoperative patient VAS score improved from 8.2 to 3.6 after surgery. The mean ODI score improved from 83.7% before surgery to 29.7% after the operation and to 36.1% at the final follow-up. No screw migration had occurred at the 1-year follow-up, but 1 screw breakage/migration was visualized on spinal radiography at the 2-year follow-up. CONCLUSIONS The results of this study show that the multiaxial expandable pedicle screw is a safe and practical technique for patients with osteoporosis and various spinal diseases and adds a valuable tool to the armamentarium of spinal instrumentation.
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Affiliation(s)
- Roberto Gazzeri
- Department of Neurosurgery, San Giovanni Addolorata Hospital, Rome, Italy
| | - Raffaelino Roperto
- Department of Neurosurgery, San Giovanni Addolorata Hospital, Rome, Italy
| | - Claudio Fiore
- Department of Neurosurgery, San Giovanni Addolorata Hospital, Rome, Italy
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WANG JIANGZE, ZHANG FENG, YOU MINGLIANG, SHA MO, LIANG BOWEI, LIANG DONGZHU, DING ZHENQI. A BIOMECHANICAL STUDY OF SHEAR LOAD ON BONE–SCREW INTERFACE OF THORACOLUMBAR VERTEBRAE. J MECH MED BIOL 2015. [DOI: 10.1142/s0219519415400412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Vertebral screw failure by cutting through or pulling out of the vertebral body is common in intraoperative and postoperative stages of anterior thoracolumbar surgery, especially in osteoporotic patients. This biomechanical study was conducted to investigate the maximum shear force thoracolumbar vertebrae can withstand and the corresponding displacement of screws and analyze their correlation with vertebral bone mineral density. Forty individual vertebra specimens (T11-L3) were obtained from eight fresh adult cadaveric thoracolumbar spine specimens and randomly divided into an experimental group and a control group. Screws were placed in the center point of vertebrae and penetrated the contralateral cortex. Shear loading and axial pullout tests were conducted on the experimental group while only axial pullout test was conducted on the control group. The maximum shear forces and maximum axial pullout forces were recorded. The conditions of vertebral body destruction and screw channel were observed and the maximum axial pullout forces were recorded and analyzed. A large amount of thread bone debris was observed in the control group. In the experimental group, however, only a small amount of thread bone debris was observed; the widths of screw paths were larger than those in the control group and gradually increased from screw tips in the direction of loading. The vertebral bodies had an average shear strength of [Formula: see text][Formula: see text]N, and the corresponding average screw displacement was [Formula: see text][Formula: see text]mm. Linear regression analysis showed that the shear strength had a significant positive correlation with vertebral bone mineral density (BMD) (r[Formula: see text][Formula: see text][Formula: see text]0.958, P[Formula: see text][Formula: see text][Formula: see text]0.01), while the screw displacement had a significant negative correlation with vertebral BMD (r[Formula: see text][Formula: see text][Formula: see text]−0.933, P[Formula: see text][Formula: see text][Formula: see text]0.01). No significant difference in bone density was found between the destruction and the control groups (P[Formula: see text][Formula: see text][Formula: see text]0.05); the difference in maximum axial pullout strength between the destruction and the control groups was significant (P[Formula: see text][Formula: see text][Formula: see text]0.01). These results indicated that vertebral BMD positively correlated with the maximum shear force and negatively with the screw displacement. It is important that the corrective strength for spinal deformity may affect bone–screw interface in anterior thoracolumbar surgery.
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Affiliation(s)
- JIANG-ZE WANG
- Department of Orthopaedics The Affiliated Southeast Hospital of Xiamen University Orthopaedic Center of the 175th Hospital of PLA Zhangzhou, Fujian 363000, P. R. China
| | - FENG ZHANG
- Department of Orthopaedics The Affiliated Southeast Hospital of Xiamen University Orthopaedic Center of the 175th Hospital of PLA Zhangzhou, Fujian 363000, P. R. China
| | - MING-LIANG YOU
- Cancer Science Institute of Singapore National University of Singapore Singapore, 117599
| | - MO SHA
- Department of Orthopaedics The Affiliated Southeast Hospital of Xiamen University Orthopaedic Center of the 175th Hospital of PLA Zhangzhou, Fujian 363000, P. R. China
| | - BO-WEI LIANG
- Department of Orthopaedics The Affiliated Southeast Hospital of Xiamen University Orthopaedic Center of the 175th Hospital of PLA Zhangzhou, Fujian 363000, P. R. China
| | - DONG-ZHU LIANG
- Guangdong Provincial Key Laboratory of Biomechanics Southern Medical University Guangzhou 510515, P. R. China
| | - ZHEN-QI DING
- Department of Orthopaedics The Affiliated Southeast Hospital of Xiamen University Orthopaedic Center of the 175th Hospital of PLA Zhangzhou, Fujian 363000, P. R. China
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Demir T. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell. Proc Inst Mech Eng H 2015; 229:386-94. [PMID: 25991716 DOI: 10.1177/0954411915584430] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective.
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Affiliation(s)
- Teyfik Demir
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
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32
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Tolunay T, Başgül C, Demir T, Yaman ME, Arslan AK. Pullout performance comparison of pedicle screws based on cement application and design parameters. Proc Inst Mech Eng H 2015; 229:786-93. [DOI: 10.1177/0954411915612494] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pedicle screws are the main fixation devices for certain surgeries. Pedicle screw loosening is a common problem especially for osteoporotic incidents. Cannulated screws with cement augmentation are widely used for that kind of cases. Dual lead dual cored pedicle screw has already given promising pullout values without augmentation. This study concentrates on the usage of dual lead dual core with cement augmentation as an alternative to cannulated and standard pedicle screws with cement augmentation. Five groups (dual lead dual core, normal pedicle screw and cannulated pedicle screw with augmentation, normal pedicle screw, dual lead dual cored pedicle screw) were designed for this study. Healthy bovine vertebrae and synthetic polyurethane foams (grade 20) were used as embedding test medium. Test samples were prepared in accordance with surgical guidelines and ASTM F543 standard testing protocols. Pullout tests were conducted with Instron 3300 testing frame. Load versus displacement values were recorded and maximum pullout loads were stated. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation exhibited the highest pullout values, while dual lead dual cored pedicle screw demonstrated similar pullout strength as cannulated pedicle screw and normal pedicle screw with poly-methyl methacrylate augmentation. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation can be used for osteoporotic and/or severe osteoporotic patients according to its promising results on animal cadaver and synthetic foams.
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Affiliation(s)
- Tolga Tolunay
- Department of Orthopaedics, Yenimahalle Education and Research Hospital, Ankara, Turkey
| | - Cemile Başgül
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
| | - Teyfik Demir
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
| | - Mesut E Yaman
- Department of Neurosurgery, Yenimahalle Education and Research Hospital, Ankara, Turkey
| | - Arslan K Arslan
- Department of Orthopaedics, Yenimahalle Education and Research Hospital, Ankara, Turkey
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VCELAK JOSEF, TICHÝ PETR, BOUDA TOMÁŠ, CHOMIAK JIŘÍ, TÓTH LADISLAV. PEDICLE SCREW CONVERGENCE IMPACT ON THE STABILITY OF TRANSPEDICULAR FIXATION SPINE MODEL IN CYCLIC LOADING: BIOMECHANICAL STUDY. J MECH MED BIOL 2015. [DOI: 10.1142/s0219519415500785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The principle of this study is experimental measurement and description of behavior of transpedicular fixation during cyclic loading due to convergence of screw insertion. Investigations were made of three configurations of assemblies of posterior stabliization with converging screws at 0°, 20° and 40°. The experiment was inspired ASTM Standard F1717 and modified to minimize the effect of other parameters. The MTS 858.2 Mini Bionix testing system was used during the experiment, in conjunction with the Interface 1010ACK load cell. Data processing and analysis were carried out by Matlab R 20102b, MathWorks. The probed assemblies were cyclically loaded until structural failure occurred, always at the screwbone (or PUR block) interface, i.e., the "windshield wiper" effect. The measurement results show that while the rigidity of the assembly increases with increased convergence of transpedicular screws, they also indicate an increased initial rate of assembly damage accumulation, together with assembly failure during a reduced number of cyclic loading cycles. The mechanical behavioral study of transpedicular fixation is limited by the conditions of simplification of interpretation of complex movements and spinal pathophysiology in the attempt to minimize the effect of other parameters and exaggerated measurements.
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Affiliation(s)
- JOSEF VCELAK
- Orthopaedic Clinic, 1st Medical Faculty, Charles University, Prague, Czech Republic
| | - PETR TICHÝ
- Orthopaedic Clinic, 1st Medical Faculty, Charles University, Prague, Czech Republic
| | - TOMÁŠ BOUDA
- Orthopaedic Clinic, 1st Medical Faculty, Charles University, Prague, Czech Republic
| | - JIŘÍ CHOMIAK
- Orthopaedic Clinic, 1st Medical Faculty, Charles University, Prague, Czech Republic
| | - LADISLAV TÓTH
- Orthopaedic Clinic, 1st Medical Faculty, Charles University, Prague, Czech Republic
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Undertapping of Lumbar Pedicle Screws Can Result in Tapping With a Pitch That Differs From That of the Screw, Which Decreases Screw Pullout Force. Spine (Phila Pa 1976) 2015; 40:E729-34. [PMID: 25856261 DOI: 10.1097/brs.0000000000000922] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Survey of spine surgeons and biomechanical comparison of screw pullout forces. OBJECTIVE To investigate what may be a suboptimal practice regularly occurring in spine surgery. SUMMARY OF BACKGROUND DATA In order for a tap to function in its intended manner, the pitch of the tap should be the same as the pitch of the screw. Undertapping has been shown to increase the pullout force of pedicle screws compared with line-to-line tapping. However, given the way current commercial lumbar pedicle screw systems are designed, undertapping may result in a tap being used that has a different pitch from that of the screw (incongruent pitch). METHODS A survey asked participants questions to estimate the proportion of cases each participant performed in the prior year using various hole preparation techniques. Participant responses were interpreted in the context of manufacturing specifications of specific instrumentation systems. Screw pullout forces were compared between undertapping with incongruent pitch and undertapping with congruent pitch using 0.16 g/cm polyurethane foam block and 6.5-mm screws. RESULTS Of the 3679 cases in which participants reported tapping, participants reported line-to-line tapping in 209 cases (5%), undertapping with incongruent pitch in 1156 cases (32%), and undertapping with congruent pitch in 2314 cases (63%). The mean pullout force for undertapping with incongruent pitch was 56 N (8%) less than the mean pullout force for undertapping with congruent pitch. This is equivalent to 13 lb. CONCLUSION This study estimates that for about 1 out of every 3 surgical cases with tapping of lumbar pedicle screws in the United States, hole preparation is being performed by undertapping with incongruent pitch. This study also shows that undertapping with incongruent pitch results in a decrease in pullout force by 8% compared with undertapping with congruent pitch. Steps should be taken to correct this suboptimal practice. LEVEL OF EVIDENCE 3.
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Tolunay T, Arslan K, Yaman O, Dalbayrak S, Demir T. Biomechanical Performance of Various Cement-Augmented Cannulated Pedicle Screw Designs for Osteoporotic Bones. Spine Deform 2015; 3:205-210. [PMID: 27927460 DOI: 10.1016/j.jspd.2014.09.055] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 09/12/2014] [Accepted: 09/17/2014] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Early-stage pullout is a common problem for surgeons during the fixation of osteoporotic bones. Poor bone quality limits the use of pedicle screws for patients with osteoporosis. In this study, the researchers investigated the effects of hole and gap position and type on the pullout strength of cannulated screws. METHODS Seven different designs were tested, including a control group. All cannula diameters were 2 mm and holes were drilled with a diameter of 1.5 mm. Gaps were milled with a 2-mm-diameter tool with 2-mm displacement proximally. All holes and gaps were drilled or opened unilaterally and bilaterally. Grade 40 and 10 polyurethane foam was used to simulate healthy and osteoporotic bones, respectively. For pullout tests, insertion depth was 30 mm and 2-mm-diameter pilot holes were drilled into blocks before screws were inserted. The cross-head speed was 2 mm/min. For torsion tests, 1 side of the screw was fixed and other was twisted clockwise. RESULTS For torsion tests, the maximum torque value exhibited by the control group (non-cannulated) was 14.94 Nm. The highest torsional strength among tested cannulated screws was 13.54 Nm for Single side two holes including design (S2H) (p < .0001). The minimum torsional strength was 9.45 Nm with a breaking angle of 39° (p < .005). Comparing results for samples pulled out from grade 40 polyurethane foam, single side slot including design (SS) samples exhibited the highest pullout strength with a maximum force of 3,104 N. CONCLUSIONS The unilateral, sequential, 3-radial hole, drilled, cannulated screw was the optimal alternative when considering pullout and torsional strength as criteria.
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Affiliation(s)
- Tolga Tolunay
- Department of Orthopaedics, Yenimahalle Training and Research Hospital, 2026. Avenue, 06370, Ankara, Turkey
| | - Kağan Arslan
- Department of Orthopaedics, Yenimahalle Training and Research Hospital, 2026. Avenue, 06370, Ankara, Turkey
| | - Onur Yaman
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Sogutozu Avenue, 06560, Ankara, Turkey
| | - Sedat Dalbayrak
- Department of Neurosurgery, Neurospinal Academy, Istanbul, Turkey
| | - Teyfik Demir
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Sogutozu Avenue, 06560, Ankara, Turkey.
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Balancing rigidity and safety of pedicle screw fixation via a novel expansion mechanism in a severely osteoporotic model. BIOMED RESEARCH INTERNATIONAL 2015; 2015:318405. [PMID: 25705655 PMCID: PMC4331393 DOI: 10.1155/2015/318405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 01/03/2015] [Accepted: 01/03/2015] [Indexed: 11/17/2022]
Abstract
Many successful attempts to increase pullout strength of pedicle screws in osteoporotic bone have been accompanied with an increased risk of catastrophic damage to the patient. To avoid this, a single-armed expansive pedicle screw was designed to increase fixation strength while controlling postfailure damage away from the nerves surrounding the pedicle. The screw was then subsequently tested in two severely osteoporotic models: one representing trabecular bone (with and without the presence of polymethylmethacrylate) and the other representing a combination of trabecular and cortical bone. Maximum pullout strength, stiffness, energy to failure, energy to removal, and size of the resulting block damage were statistically compared among conditions. While expandable pedicle screws produced maximum pullout forces less than or comparable to standard screws, they required a higher amount of energy to be fully removed from both models. Furthermore, damage to the cortical layer in the composite test blocks was smaller in all measured directions for tests involving expandable pedicle screws than those involving standard pedicle screws. This indicates that while initial fixation may not differ in the presence of cortical bone, the expandable pedicle screw offers an increased level of postfailure stability and safety to patients awaiting revision surgery.
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Zhou CS, Xu YF, Zhang Y, Chen Z, Lv H. Biomechanical testing of a unique built-in expandable anterior spinal internal fixation system. BMC Musculoskelet Disord 2014; 15:424. [PMID: 25496488 PMCID: PMC4295300 DOI: 10.1186/1471-2474-15-424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 12/05/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Expandable screws have greater pullout strength than conventional screws. The purpose of this study was to compare the biomechanical stability provided by a new built-in expandable anterior spinal fixation system with that of 2 commonly used anterior fixation systems, the Z-Plate and the Kaneda, in a porcine partial vertebral corpectomy model. METHODS Eighteen porcine thoracolumbar spine specimens were randomly divided into 3 groups of 6 each. A vertebral wedge osteotomy was performed by removing the anterior 2/3 of the L1 vertebral body and the T15/L1 disc. Vertebrae were fixed with the Z-Plate, Kaneda, or expandable fixation system. The 3-dimensional spinal range of motion (ROM) of specimens in the intact state (prior to osteotomy), injured state (after osteotomy), and after internal fixation were recorded. The pullout strength and maximum torque of common anterior screws, the expandable anterior fixation screw unexpanded, and the expandable anterior fixation screw expanded was tested. RESULTS After internal fixation, the expandable device and Z-plate system exhibited higher left bending motion than the Kaneda system (5.50° and 5.37° vs. 5.04, p = 0.001 and 0.008, respectively), and the Z-plate and Kaneda groups had significantly higher left axial and right axial rotation ROM as compared to the expandable device group (left axial rotation: 5.23° and 5.02° vs. 4.53°; right axial rotation: 5.23° and 5.08° vs. 4.49°). The maximum insertion torque of the expandable device was significantly greater than of a common screw (5.10 vs. 3.75 Ns). The maximum pullout force of the expandable device expanded was significantly higher than that of the common screw and the expandable device unexpanded (3,035.48 N vs. 1,827.38 N and 2,333.49 N). CONCLUSIONS The built-in anterior fixation system provides better axial rotational stability as compared to the other 2 systems, and greater maximum torque and pullout strength than a common fixation screw.
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Affiliation(s)
| | - Yan-Fang Xu
- Department of Orthopaedics, The Second People's Hospital of Changzhi City, No 83 Speace West Street, Changzhi City, Shanxi 046000, People's Republic of China.
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Designs and techniques that improve the pullout strength of pedicle screws in osteoporotic vertebrae: current status. BIOMED RESEARCH INTERNATIONAL 2014; 2014:748393. [PMID: 24724097 PMCID: PMC3958762 DOI: 10.1155/2014/748393] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 01/16/2014] [Accepted: 01/22/2014] [Indexed: 12/21/2022]
Abstract
Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein.
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Amaritsakul Y, Chao CK, Lin J. Comparison study of the pullout strength of conventional spinal pedicle screws and a novel design in full and backed-out insertions using mechanical tests. Proc Inst Mech Eng H 2014; 228:250-7. [DOI: 10.1177/0954411914522437] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recently, new pedicle screw designs have been developed. However, these designs’ performances are still unclear, especially when backed out after insertion. The objective of this study was to investigate the performances of different screw designs when backed out from full insertion. Seven conventional designs of the pedicle screw and one novel design were inserted into polyurethane foam (0.32 g/cm3). All screws were first fully inserted (43 mm) and were backed out 360°. Axial pullout tests were performed and the reaction force was measured. The results showed that the conical screw of type 1 with a small inner diameter provided the highest pullout strength in both full insertion and backed-out insertion (2401.85 and 2169.82 N, respectively). However, this screw’s pullout strength significantly decreased (9.7%) when backed out from full insertion. There was no significant difference between the conical screw of type 1 with a small inner diameter and double duo core screw ( p > 0.01) in backed-out insertion. The cylindrical screw with a small diameter, dual inner core screw and double dual core screw also provided good results in both full insertion (2115.44, 2182.99 and 2226.93 N, respectively) and backed-out conditions (2065.80, 2014.28 and 1941.29 N, respectively). The increased pullout strength of the conical design could be due to the effect of bone compaction. However, the screw exhibited less consistent pullout strength when backed out when compared with the other designs. The conical screw should be inserted to the precise position without turning back, especially in osteoporosis patients. The dual inner core screw and double dual core screw could provide greater stability in both conditions. Care should be taken when using both the cylindrical screw with a small thread depth and the dual outer core screw.
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Affiliation(s)
- Yongyut Amaritsakul
- Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, ROC
| | - Ching-Kong Chao
- Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, ROC
| | - Jinn Lin
- Department of Orthopedic Surgery, National Taiwan University Hospital, Taipei, Taiwan, ROC
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Rovira Gutierrez M, Gonzalez MF, Villar Perez J, Perez Varela L, Pascua LH, Alia Benitez J, Ignacio ED, Quintana Cruz JJ, Zuñiga Gomez L, Izquierdo Nuñez E. Utilización de un nuevo tornillo expansivo en pacientes con mala calidad ósea: estudio multicéntrico. COLUNA/COLUMNA 2013. [DOI: 10.1590/s1808-18512013000400010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
OBJETIVO: Observar el comportamiento del tornillo expansivo en pacientes con mala calidad ósea, su seguridad, técnica, manejo y complicaciones: porcentaje de aflojamiento, roturas, "pull-out" y pseudartrosis. MÉTODOS: Realizamos estudio prospectivo multicéntrico analizando factores de riesgo del paciente, VAS, tiempo quirúrgico, pérdida de sangre, emplazamiento de tornillos y complicaciones debidas al implante a la alta y a los 3, 12 y 24 meses. RESULTADOS: El 99% de los pacientes no tuvieron ninguna complicación permanente relacionada con el implante; sólo hubo un caso de radiculopatía no resuelta. En el 95% de los implantes, los tornillos se colocaron sin complicaciones; en el 5% aparecieron complicaciones relacionadas con la mala colocación o expansión del tornillo, resueltas en acto quirúrgico. Tiempo quirúrgico promedio por nivel, 56 min.; tiempo promedio por intervención, 2 horas 35 min. Sangramiento promedio por nivel intervenido, 211cc. Hemos tenido tres casos de "pull-out". El VAS evolucionó favorablemente de forma significativa, con reducciones promedio mayores a cuatro puntos. El estudio continuará hasta los cinco años, siendo estos los resultados preliminares. CONCLUSIONES: Este tipo de tornillos expansivos aportan un nuevo sistema de anclaje para pacientes con mala calidad ósea; son seguros y eficaces, ofrecen rapidez en su colocación, una menor exposición a los RXy, en caso de retirada del tornillo, dejan el camino libre para una nueva cirugía.
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Koller H, Zenner J, Hitzl W, Resch H, Stephan D, Augat P, Penzkofer R, Korn G, Kendell A, Meier O, Mayer M. The impact of a distal expansion mechanism added to a standard pedicle screw on pullout resistance. A biomechanical study. Spine J 2013; 13:532-41. [PMID: 23415899 DOI: 10.1016/j.spinee.2013.01.038] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 07/13/2012] [Accepted: 01/13/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Spinal deformity surgery in elderly patients is associated with an increased risk of implant loosening due to failure at the screw-bone interface. Several techniques can be used to increase the screw anchorage characteristics. Cement-augmented screw fixation was shown to be the most efficient method; however, this technique is associated with a risk of complications related to vertebral cement deposition and leakage. Hence, there is a need to further elaborate the alternative screw augmenting techniques to reduce the indications for bone cement. PURPOSE To analyze surgical alternatives to cement augmentation, the present study sought to quantify the impact of a distal expansion mechanism added to a standard pedicle screw on an axial pullout resistance. STUDY DESIGN A biomechanical laboratory study on the uniaxial pullout resistance of a standard pedicle screw versus a customized pedicle screw with a distal expansion mechanism. METHODS A total of 40 vertebrae from seven fresh-frozen human specimens were harvested and subjected to a computed tomography scanning and an analysis of the bone mineral density (BMD). The vertebrae were instrumented with a standard 6.0-mm pedicle screw and a modified 6.0-mm pedicle screw with a distal expansion mechanism added. The actual working length of both screws inside the vertebrae was identical. The distal expansion mechanism made up one-fifth of the shaft length. The accuracy of the screw insertion was assessed using biplanar radiographs and by inspection. Analysis of resistance to pullout was performed by a coaxial alignment of the pedicle screws and attachment to an electromechanical testing machine. The pullout rate was 5 mm/min, and the load-displacement curve was recorded until the force of the pullout resistance peaked. The peak load-to-failure was measured in Newtons and reported as the ultimate failure load. With each test, the mode of failure was noted and analyzed descriptively. RESULTS A total of 17 vertebrae with matched pairs of standard and expansion pedicle screws were eligible for the final statistical analysis. The BMD of the vertebrae tested was 0.67±0.19 g/cm³. The screw length was 50 mm, and the actual working length of both screws was 40.3±4.2 mm. The ultimate failure load of the standard screw was 773.8±529.4 N and that of the expansion screw was 910.3±488.3 N. Statistical analysis revealed a strong trend toward an increased failure load with the expansion screw (p=.06). The mean increase of the ultimate failure load was 136.5±350.4 N. Abrupt vertebral fracture at the vertebral body-pedicle junction and the pedicle occurred seven times with the expansion screw and only five times with the standard screw (p=.16). CONCLUSIONS Our study indicates that adding a distal expansion mechanism to a standard pedicle screw increases the failure load by one-fifth. Modern expansion screws might offer an intermediate solution for the augmentation of screw-rod constructs in osteoporotic bone while reducing the need for cement-augmented screws and avoiding the related risks.
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Affiliation(s)
- Heiko Koller
- German Scoliosis Center Bad Wildungen, Werner-Wicker-Clinic, Im Kreuzfeld 4, D-34537, Bad Wildungen, Germany.
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Comparison of teriparatide and bisphosphonate treatment to reduce pedicle screw loosening after lumbar spinal fusion surgery in postmenopausal women with osteoporosis from a bone quality perspective. Spine (Phila Pa 1976) 2013; 38:E487-92. [PMID: 23354115 DOI: 10.1097/brs.0b013e31828826dd] [Citation(s) in RCA: 186] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Prospective study. OBJECTIVE To examine the efficacy of teriparatide or bisphosphonate treatment to reduce pedicle screw (PS) loosening after instrumented lumbar posterolateral fusion in postmenopausal women with osteoporosis. SUMMARY OF BACKGROUND DATA Failure of fixation caused by loosening of PSs in osteoporosis is a problem in spinal surgery. Oral administration of bisphosphonate or intermittent injection of parathyroid hormone treatment increases bone mass and reduces the risk of osteoporotic vertebral fractures. Although these treatments may be factor in improving bone quality, a clinical study of the efficacy of bisphosphonate or parathyroid hormone for reducing PS loosening that addresses the quality of the bone marrow and pedicle cortex has not yet been reported. METHODS Sixty-two women with osteoporosis diagnosed with degenerative spondylolisthesis were divided into 3 groups: a teriparatide group (daily subcutaneous injection of 20 μg of teriparatide, n = 20), a bisphosphonate group (daily oral administration 2.5 mg of risedronate, n = 20), and a control group (without medication for osteoporosis, n = 22). All patients underwent decompression and 1- or 2-level instrumented posterolateral fusion with a local bone graft. Loosening of PSs and surgical outcome were evaluated radiographically, clinically, and by computed tomography 12 months after surgery. RESULTS At 12-month follow-up, the incidence of PS loosening was 7% to 13% in the teriparatide group, 13% to 26% in the risedronate group, and 15% to 25% in the control group. The incidence of PS loosening in the teriparatide group was significantly lower than that in the risedronate or the control group (P < 0.05). In contrast, the extent of PS loosening in the risedronate group was not significantly different from that in the control group (P > 0.05). CONCLUSION Our findings suggest that administration of teriparatide increased the quality of the lumbar spine bone marrow and pedicle cortex.
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Steib JP, Schuller S. Ostéosynthèse du rachis : évolution des matériels et des techniques. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/s0246-0467(12)58654-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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