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Okamoto N, Okazaki R, Azuma S, Oshima Y. Clinical role of crosslink augmentation during short-segment posterior lumbar interbody fusion with total facetectomy: A propensity score-matched analysis. J Clin Neurosci 2024; 120:48-54. [PMID: 38185006 DOI: 10.1016/j.jocn.2023.12.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 12/30/2023] [Indexed: 01/09/2024]
Abstract
We investigated the clinical role of crosslink augmentation during PLIF with total facetectomy. We retrospectively reviewed 376 patients who underwent one- or two-segment PLIF with unilateral or bilateral total facetectomy between January 2017 and March 2022. The patients were categorized into two groups based on whether a crosslink was instrumented or not. Radiological outcome measurements included fusion status and implant failure rates on 12-month postoperative computed tomography. Patient-reported outcome measures included the Numerical Rating Scale for lower back pain, Oswestry Disability Index, and Short Form-12 Physical Component Summary scores, which were assessed preoperatively and at 12 months postoperatively. Surgery-related complications included surgical site infection, symptomatic implant failure, and epidural hematoma. Propensity score matching was performed to compare both groups after adjusting for confounding factors, including baseline and surgical procedural characteristics. A total of 200 cases were included in the propensity score calculation, and one-to-one matching was performed, resulting in 56 pairs with and without a crosslink. The fusion status (88.7 % vs. 85.5 %), screw loosening (14.3 % vs. 14.3 %), cage subsidence (17.9 % vs. 16.1 %), and cage dislodgement (5.4 % vs. 0 %) showed no significant difference between those with and without a crosslink, respectively. No significant differences were observed in the patient-reported outcomes or surgery-related complication rates between the groups. Crosslink augmentation during PLIF with total facetectomy is not recommended because it does not provide any radiological or clinical benefit and is associated with avoidable expenses.
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Affiliation(s)
- Naoki Okamoto
- Department of Orthopaedic Surgery, Japanese Red Cross Saitama Hospital, Saitama, Japan 1-5 Shintoshin, Chuo-ku, Saitama 330-0081, Japan; University of Tokyo Spine Group (UTSG), 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan.
| | - Rentaro Okazaki
- Department of Orthopaedic Surgery, Japanese Red Cross Saitama Hospital, Saitama, Japan 1-5 Shintoshin, Chuo-ku, Saitama 330-0081, Japan; University of Tokyo Spine Group (UTSG), 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan
| | - Seiichi Azuma
- Department of Orthopaedic Surgery, Japanese Red Cross Saitama Hospital, Saitama, Japan 1-5 Shintoshin, Chuo-ku, Saitama 330-0081, Japan; University of Tokyo Spine Group (UTSG), 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan
| | - Yasushi Oshima
- University of Tokyo Spine Group (UTSG), 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan; Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan.
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Han Y, Ren X, Liang Y, Ma X, Wang X. Biomechanical effects of transverse connectors on total en bloc spondylectomy of the lumbar spine: a finite element analysis. J Orthop Surg Res 2023; 18:484. [PMID: 37408002 DOI: 10.1186/s13018-023-03977-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/03/2023] [Indexed: 07/07/2023] Open
Abstract
BACKGROUND The influence of total en bloc spondylectomy (TES) on spinal stability is substantial, necessitating strong fixation to restore spinal stability. The transverse connector (TC) serves as a posterior spinal instrumentation that connects the left and right sides of the pedicle screw-rod system. Several studies have highlighted the potential of a TC in enhancing the stability of the fixed segments. However, contradictory results have suggested that a TC not only fails to improve the stability of the fixed segments but also might promote stress associated with internal fixation. To date, there is a lack of previous research investigating the biomechanical effects of a TC on TES. This study aimed to investigate the biomechanical effects of a TC on internal fixation during TES of the lumbar (L) spine. METHODS A single-segment (L3 segment) TES was simulated using a comprehensive L spine finite element model. Five models were constructed based on the various positions of the TC, namely the intact model (L1-sacrum), the TES model without a TC, the TES model with a TC at L1-2, the TES model with a TC at L2-4, and the TES model with a TC at L4-5. Mechanical analysis of these distinct models was conducted using the Abaqus software to assess the variations in the biomechanics of the pedicle screw-rod system, titanium cage, and adjacent endplates. RESULTS The stability of the surgical segments was found to be satisfactory across all models. Compared with the complete model, the internal fixation device exhibited the greatest constraint on overextension (95.2-95.6%), while showing the least limitation on left/right rotation (53.62-55.64%). The application of the TC had minimal effect on the stability of the fixed segments, resulting in a maximum reduction in segment mobility of 0.11° and a variation range of 3.29%. Regardless of the use of a TC, no significant changes in stress were observed for the titanium cage. In the model without the TC, the maximum von Mises stress (VMS) for the pedicle screw-rod system reached 136.9 MPa during anterior flexion. Upon the addition of a TC, the maximum VMS of the pedicle screw-rod system increased to varying degrees. The highest recorded VMS was 459.3 MPa, indicating a stress increase of 335.5%. Following the TC implantation, the stress on the adjacent endplate exhibited a partial reduction, with the maximum stress reduced by 27.6%. CONCLUSION The use of a TC in TES does not improve the stability of the fixed segments and instead might result in increased stress concentration within the internal fixation devices. Based on these findings, the routine utilisation of TC in TES is deemed unnecessary.
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Affiliation(s)
- Ye Han
- Department of Orthopaedics, Affiliated Hospital of Hebei University, No. 212, Yuhua Road, Hebei, Baoding City, 071000, China
| | - Xuehong Ren
- Hebei University, Hebei, Baoding City, China
| | - Yijie Liang
- Hebei University, Hebei, Baoding City, China
| | - Xiaoyong Ma
- Department of Orthopaedics, Affiliated Hospital of Hebei University, No. 212, Yuhua Road, Hebei, Baoding City, 071000, China
| | - Xiaodong Wang
- Department of Orthopaedics, Affiliated Hospital of Hebei University, No. 212, Yuhua Road, Hebei, Baoding City, 071000, China.
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Is it a requirement or a preference to use cross-links in lumbar instrumentation? JOURNAL OF SURGERY AND MEDICINE 2022. [DOI: 10.28982/josam.7446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Background/Aim: The use of cross-links (CL) is controversial due to reasons such as cost increases and instrument redundancy. While there are many biomechanical studies, the clinical data is limited. The aim of this study is to present the clinical effects of CL by putting forward postoperative clinical outcomes and long-term results of patients with (CL+) and without (CL-) CL augmentation.
Methods: In this retrospective cohort study, patients who underwent lumbar posterior instrumentation with CL+ (n = 164) and without CL- (n = 111) augmentation were evaluated. Demographic data, surgical results, preoperative and postoperative visual analogue scale (VAS), the Oswestry Disability Index (ODI) differences, and pseudoarthrosis and adjacent segment disease (ASD)-related recurrence for more than three years of follow-up were determined. Data of CL+ and CL- groups were compared.
Results: CL+ and CL- groups were similar in terms of age and gender (P = 0.319 and P = 0.777, respectively) There was no difference between the two groups in terms of bleeding amount, duration of surgery, and duration of hospitalization (P = 0.931, P = 0.669 and P = 0.518, respectively). Groups were similar in terms of VAS and ODI differences (P = 0.915 and P = 0.983, respectively), yet there was one case of infection in the CL+ group and two cases of infection detected in the CL- group. There were 13 ASDs in the CL+ group, and eight ASDs in the CL- group. Pseudoarthrosis was seen seven times in the CL+ group, while it was four in the CL- group.
Conclusion: It was observed that adding CL in patients who underwent lumbar instrumentation did not change the early period surgical results. The prevalence of complications was compatible with the scientific literature. In our study, there was no preventive advantage in terms of clinical or postoperative complications found in the use of CL.
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Han L, Yang H, Li Y, Li Z, Ma H, Wang C, Yuan J, Zheng L, Chen Q, Lu X. Biomechanical Evaluation of the Cross-link Usage and Position in the Single and Multiple Segment Posterior Lumbar Interbody Fusion. Orthop Surg 2022; 14:2711-2720. [PMID: 36102202 PMCID: PMC9531066 DOI: 10.1111/os.13485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 07/28/2022] [Accepted: 08/09/2022] [Indexed: 12/29/2022] Open
Abstract
OBJECTIVE Previous studies have neither explored the usage of cross-links nor investigated the optimal position of the cross-links in posterior lumbar interbody fusion (PLIF). This study evaluates biomechanical properties of cross-links in terms of different fixation segments and optimal position in single- and multi-segment posterior lumbar interbody fusion. METHODS Two finite element (FE) models of instrumented lumbosacral spine with single-(L4/5) and multi-segment (L3-S1) PLIF surgery were simulated. On the basis of the two models, the benefits of the usage of cross-links were assessed and compared with the status of no application of cross-links. Moreover, the effects of position of cross-links on multi-segment PLIF surgery were studied in Upper, Middle, and Lower positions. RESULTS No significant difference was found in the range of motion (ROM), intersegmental rotational angle (IRA) of adjacent segments, and intradiscal pressure (IDP) regardless of the usage of cross-links in the single-segment PLIF surgery, while the cross-link increased the maximum von Mises stress in the fixation (MSF) under the axial rotation (53.65 MPa vs 41.42 MPa). In the multi-segment PLIF surgery, the usage of cross-links showed anti-rotational advantages indicated by ROM (Without Cross-link 2.35o , Upper, 2.24o ; Middle, 2.26o ; Lower, 2.30o ) and IRA (Without Cross-link 1.19o , Upper, 1.08o ; Middle, 1.09o ; Lower, 1.13o ). The greatest values of MSF were found in without cross-link case under the flexion, lateral bending, and axial rotation (37.48, 62.61, and 86.73 MPa). The application of cross-links at the Middle and Lower positions had lower values of MSF (48.79 and 69.62 MPa) under the lateral bending and axial rotation, respectively. CONCLUSION The application of cross-links was not beneficial for the single-segment PLIF, while it was found highly advantageous for the multi-segment PLIF. Moreover, the usage of cross-links at the Middle or Lower positions resulted in a better biomechanical stability.
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Affiliation(s)
- Lin Han
- Department of OrthopaedicsShanghai Changzheng Hospital, Second Military Medical UniversityShanghaiChina
| | - Haisong Yang
- Department of OrthopaedicsShanghai Changzheng Hospital, Second Military Medical UniversityShanghaiChina
| | - Yongheng Li
- Biomechanics LaboratorySchool of Biological Science & Medical Engineering, Southeast UniversityNanjingChina
| | - Zhiyong Li
- Biomechanics LaboratorySchool of Biological Science & Medical Engineering, Southeast UniversityNanjingChina,School of Mechanical Medical and Process Engineering, Queensland University of TechnologyBrisbaneAustralia
| | - Hongdao Ma
- Department of OrthopaedicsShanghai Changzheng Hospital, Second Military Medical UniversityShanghaiChina
| | - Chenfeng Wang
- Department of OrthopaedicsShanghai Changzheng Hospital, Second Military Medical UniversityShanghaiChina
| | - Jincan Yuan
- Department of OrthopaedicsShanghai Changzheng Hospital, Second Military Medical UniversityShanghaiChina
| | - Luyu Zheng
- School of Medicine, Zhengzhou UniversityZhengzhouChina
| | - Qiang Chen
- Biomechanics LaboratorySchool of Biological Science & Medical Engineering, Southeast UniversityNanjingChina
| | - Xuhua Lu
- Department of OrthopaedicsShanghai Changzheng Hospital, Second Military Medical UniversityShanghaiChina
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Kanno H, Onoda Y, Hashimoto K, Aizawa T, Ozawa H. Reinforcement of Percutaneous Pedicle Screw Fixation with Hydroxyapatite Granules in Patients with Osteoporotic Spine: Biomechanical Performance and Clinical Outcomes. Medicina (B Aires) 2022; 58:medicina58050579. [PMID: 35629996 PMCID: PMC9147225 DOI: 10.3390/medicina58050579] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/01/2022] [Accepted: 04/19/2022] [Indexed: 11/16/2022] Open
Abstract
In percutaneous pedicle screw (PPS) fixation of the osteoporotic spine, rigid screw fixation obtaining strong stabilization is important for achieving successful treatment outcomes. However, in patients with severe osteoporosis, it is difficult to obtain PPS fixation with sufficient stability. PPS fixation has potential disadvantages with respect to maintaining secure stabilization in comparison to conventional pedicle screw fixation. In PPS fixation, bone grafting to achieve posterior spine fusion is generally not applicable and transverse connectors between the rods cannot be used to reinforce the fixation. Various augmentation methods, including additional hooks, sublaminar bands, and hydroxyapatite (HA) sticks, are available for conventional pedicle screw fixation. On the other hand, there has been no established augmentation method for PPS fixation. Recently, we developed a novel augmentation technique for PPS fixation using HA granules. This technique allows the percutaneous insertion of HA granules into the screw hole along the guidewire prior to insertion of the PPS. We have used this augmentation technique for PPS fixation in various spine surgeries in patients with osteoporosis. In our previous studies, biomechanical analyses demonstrated that PPS fixation was significantly enhanced by augmentation with HA granules in the osteoporotic lumbar spine. Furthermore, augmentation with HA granules was considered to decrease the incidence of screw loosening and implant failure following PPS fixation in patients with osteoporotic spine. In this article, we describe the surgical procedures of the augmentation method using HA granules and summarize our data from the biomechanical analysis of augmentation for PPS fixation. We also review the surgical outcomes of PPS fixation with augmentation using HA granules.
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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.)
- Correspondence:
| | - 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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Wu Z, Schwend RM, Anderson JT, Marasigan JAM, Price NJ. Iliac screw instrumentation to the pelvis in children with neuromuscular and syndromic scoliosis. No lateral connectors and respect sagittal balance. Spine Deform 2021; 9:1115-1123. [PMID: 33492654 DOI: 10.1007/s43390-021-00287-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 01/03/2021] [Indexed: 11/30/2022]
Abstract
STUDY DESIGN One-center retrospective cohort study. BACKGROUND Compared to the traditional iliac screw technique, the modified iliac screw technique has a lower rate of distal implant failure in the treatment of neuromuscular scoliosis patients with pelvic obliquity. However, the reasons for decreased failure with the modified iliac screw technique are controversial. QUESTIONS/PURPOSES (1) Is distal implant failure, as evident by implant breakage or disconnection, more likely to occur in patients receiving the traditional iliac screw technique (PSIS) compared to the modified S2AI (MODS2) technique? (2) After controlling for relevant confounding variables, are there other identifiable risk factors for distal implant failure? METHODS We identified patients who underwent pelvic screw fixation by three pediatric spine surgeons from January 2007 to July 2017. Based on the starting point of the iliac screws, patients were divided into two groups. Group 1 consisted of PSIS fixation with an offset connector. Group 2 consisted of modified S2AI fixation without an offset connector. Demographic, operative, and radiographic data were obtained. RESULTS Cobb angle, lumbar lordosis, and pelvic obliquity were not significantly different between the two groups. Overall distal implant failure was 40/100 (40%) and significant between Group 1 PSIS 29/53 (55%) and Group 2 MODS2 11/47 (23%) (p = 0.002). No other complications were significant. Three risk factors were identified with implant failure: high pelvic incidence (17-fold increase, 95% confidence interval [CI] = 5.5 to 53.1, p < 0.001), high angle rod contour (3.8-fold increase, 95% CI = 1.2 to 11.9, p = 0.023), and use of an offset connector (3.2-fold increase, 95% CI = 1.0 to 10.3, p = 0.049). Failure did not correlate with the use of a cross-link, iliac screw diameter, or screw density. Revision surgery related to distal implant failure did not significantly differ between the two groups. CONCLUSIONS Compared to the use of an offset connector with PSIS fixation, MODS2 fixation had a lower rate of implant failure. Sagittal balance parameters, namely pelvic incidence and angle of rod bend, were the major risk factors for implant failure. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Zhenkai Wu
- Department of Orthopaedic Surgery, School of Medicine, Children's Mercy Kansas City, 2401 Gillham Road, Kansas City, MO, 64108, USA.,Department of Pediatric Orthopaedics, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, No. 1665, Kongjiang Road, Shanghai, 200092, China
| | - Richard M Schwend
- Department of Orthopaedic Surgery and Musculoskeletal Medicine, Children's Mercy Kansas City, 2401 Gillham Road, Kansas City, MO, 64108, USA.
| | - John T Anderson
- Department of Orthopaedic Surgery and Musculoskeletal Medicine, Children's Mercy Kansas City, 2401 Gillham Road, Kansas City, MO, 64108, USA
| | - Joanne Abby M Marasigan
- Orthopaedic Surgery Department and Musculoskeletal Medicine, University of Missouri-Kansas City School of Medicine, 2301 Holmes Road, Kansas City, MO, 64108, USA
| | - Nigel J Price
- Department of Orthopaedic Surgery and Musculoskeletal Medicine, Children's Mercy Kansas City, 2401 Gillham Road, Kansas City, MO, 64108, USA
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Al-Qahtani AN, Al Aqeely KS, Alamari Z, Al Eissa S, Alhelal F, Alhandi AA, Konbaz F. The Current Practice of Adult Idiopathic Scoliosis Surgical Treatment Among Spine Surgeons in Saudi Arabia. Cureus 2020; 12:e11552. [PMID: 33224682 PMCID: PMC7676947 DOI: 10.7759/cureus.11552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Background: Scoliosis is a spinal deformity consisting of lateral curvature and rotation of the vertebrae. The goal of corrective scoliosis surgery is to restore alignment of the spine and maintain motion. However, there is no global agreement among spine surgeons on the best method of surgical intervention, and little is known about the variations in practice among spine surgeons in Saudi Arabia. Objectives: The aim of this study is to examine the current surgical practices relating to adolescent idiopathic scoliosis and to establish the degree of variation and consensus among spine surgeons in Saudi Arabia. Methods: This was a cross-sectional study conducted among spine surgeons in Saudi Arabia, using a self-administered questionnaire. The questionnaire addressed four areas: surgeons’ demographics, pre-operative assessment, operative assessment, and infection control practices. There were a total of 27 questions. Data was analyzed using statistical package for social sciences (SPSS) software (SPSS Inc., Chicago, IL, USA). Results: A total of 150 surgeons were included in this study. Of these, 73 responded to the questionnaire (response rate: 48.6%), 46 (63.01%) of whom were fellows. All respondents were males, and 37 (51.39%) were aged between 30 and 40 years. Fifty five (75.34%) were orthopedic surgeons. The most commonly used pre-operative health assessment test was an echocardiogram. Sixty six (90%) surgeons requested scoliosis anteroposterior (AP) view and lateral radiograph for curvature between 40 degrees and 90 degrees, and 65 (89%) requested it for curvature greater than 90 degrees. For the posterior construct, 29 (45.31%) did not use cross-links for fewer than 10 levels, and 23 (35.94%) did not use cross-links for more than 10 levels. In addition to a local bone graft, the most commonly used transplant method was allograft 37 (50.68%). Fifty five (85.94%) respondents favored an all-screw pedicle construct over a hybrid construct. Conclusion: A large variation in surgical practices was observed. This was especially apparent in practices including the use of cross-links, intra-operative cell salvage, and the intra-operative use of traction. Some degree of variation was observed in pre-operative imaging assessment practices. Surgical guidelines should be developed to build a consensus among surgeons. A unified surgical training curriculum may help in achieving this goal.
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Affiliation(s)
- Abdullah N Al-Qahtani
- Medicine, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
| | - Khalid S Al Aqeely
- Orthopaedics, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
| | - Zeyad Alamari
- Orthopaedics, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
| | - Sami Al Eissa
- Orthopaedics, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
| | - Fahad Alhelal
- Orthopaedics, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
| | - Ali A Alhandi
- Orthopaedics, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
| | - Faisal Konbaz
- Orthopaedics, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, SAU
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Cornaz F, Widmer J, Snedeker JG, Spirig JM, Farshad M. Cross-links in posterior pedicle screw-rod instrumentation of the spine: a systematic review on mechanical, biomechanical, numerical and clinical studies. 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 2020; 30:34-49. [DOI: 10.1007/s00586-020-06597-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 05/13/2020] [Accepted: 09/05/2020] [Indexed: 12/14/2022]
Abstract
Abstract
Purpose
Dorsal screw-rod instrumentations are used for a variety of spinal disorders. Cross-links (CL) can be added to such constructs, however, no clear recommendations exist. This study aims to provide an overview of the available evidence on the effectiveness of CL, potentially allowing to formulate recommendations on their use.
Methods
A systematic literature review was performed on PubMed and 37 original articles were included and grouped into mechanical, biomechanical, finite element and clinical studies. The change in range of motion (ROM) was analyzed in mechanical and biomechanical studies, ROM, stiffness and stress distribution were evaluated in finite element studies and clinical outcome parameters were analyzed in clinical studies.
Results
A relative consistent reduction in ROM in axial rotation with CL-augmentation was reported, while minor and less consistent effects were observed in flexion–extension and lateral bending. The use of CLs was clinical beneficial in C1/2 fusion, while the limited clinical studies on other anatomic regions show no significant benefit for CL-augmentation.
Conclusion
While CL provides some additional axial rotation stability in most situations, lateral bending and flexion–extension are less affected. Based on clinical data, CL-augmentation can only be recommended for C1/2 instrumentations, while for other cases, further clinical studies are needed to allow for evidence-based recommendations.
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Li T, Ma C, Du YQ, Qiao GY, Yu XG, Yin YH. The Role of Transverse Connectors in C1-C2 fixation for Atlantoaxial Instability: Is It Necessary? A Biomechanical Study. World Neurosurg 2020; 140:e212-e218. [PMID: 32438009 DOI: 10.1016/j.wneu.2020.04.247] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate the biomechanical effect of C1 lateral mass-C2 pedicle screw-rod (C1LM-C2PS) fixation with and without transverse connectors (TC) in an atlantoaxial instability (AAI) model. METHODS Ten freshly frozen cadaveric specimens were tested using an industrial robot under the following conditions: intact model, AAI model, C1-C2 model, C1-C2 with one TC model, and C1-C2 with two TCs model. Three types of motion, flexion-extension (FE), lateral bending (LB), and axial rotation (AR), were applied (1.5 Nm) to the specimens. The range of motion (ROM) and neutral zone (NZ) between C1 and C2 in all directions were measured. RESULTS Compared with those of the intact and AAI models, the C1-C2 ROM and NZ of all instrumented groups were decreased significantly in each direction of loading motion (P < 0.05). The mean FE ROM in the no TC, 1 TC, and 2 TC groups was 2.12° ± 0.41°, 2.29° ± 0.42°, and 2.04° ± 0.69°, respectively (P = 0.840, 0.981, 0.628, respectively); the mean LB ROM in the 3 intervention groups was 1.26° ± 0.67°, 1.02° ± 0.51° and 1.03° ± 0.57°, respectively (P = 0.489, 0.501, 1.000, respectively). During AR, the ROM and NZ of the no TC group (3.19° ± 0.89° and 1.51° ± 0.42°) were significantly reduced by more than 60% compared with those in the 1 (0.98° ± 0.28° and 0.40° ± 0.11°) and 2 TC groups (1.17° ± 1.69° and 0.42° ± 0.61°) (P < 0.001). Two TCs were equivalent for all loading motions to 1 TC (P > 0.05). CONCLUSIONS Adding TCs to C1LM-C2PS can effectively decrease the axial rotation ROM and enhance the stability of C1-C2 segment. Therefore, it is necessary to use TC-strengthened C1 lateral mass -C2 pedicle screw-rod fixation in patients with instability of C1-C2.
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Affiliation(s)
- Teng Li
- Department of Neurosurgery, The First Medical Centre, Chinese PLA General Hospital, Beijing, China
| | - Chao Ma
- Key Laboratory of Modern Measurement and Control Technology, Ministry of Education, Beijing Information Science and Technology University, Beijing, China
| | - Yue-Qi Du
- Department of Neurosurgery, The First Medical Centre, Chinese PLA General Hospital, Beijing, China
| | - Guang-Yu Qiao
- Department of Neurosurgery, The First Medical Centre, Chinese PLA General Hospital, Beijing, China
| | - Xin-Guang Yu
- Department of Neurosurgery, The First Medical Centre, Chinese PLA General Hospital, Beijing, China
| | - Yi-Heng Yin
- Department of Neurosurgery, The First Medical Centre, Chinese PLA General Hospital, Beijing, China.
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Novel augmentation technique of percutaneous pedicle screw fixation using hydroxyapatite granules in the osteoporotic lumbar spine: a cadaveric biomechanical analysis. 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 2020; 30:71-78. [PMID: 32424638 DOI: 10.1007/s00586-020-06451-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 04/05/2020] [Accepted: 05/05/2020] [Indexed: 10/24/2022]
Abstract
PURPOSE Percutaneous pedicle screw (PPS) fixation has been commonly used for various spine surgeries. Rigid PPS fixation is necessary to decrease the incidence of screw loosening in osteoporotic spine. Recently, we have reported biomechanical advantages of augmentation technique using hydroxyapatite (HA) granules for PPS fixation in synthetic bone. However, its biomechanical performance in augmenting PPS fixation for osteoporotic spine has not been fully elucidated. The aim of the present study is to perform a cadaveric biomechanical analysis of PPS fixation augmented with HA granules. METHODS Thirty osteoporotic lumbar vertebrae (L1-L5) were obtained from 6 cadavers (3 men and 3 women; age 80 ± 9 years; bone mineral density 73 ± 9 mg/cm3). The maximal pullout strength and maximal insertion torque were compared between the screws inserted into the vertebrae with and without augmentation. In toggle testing, the number of craniocaudal toggle cycles and maximal load required to achieve the 2-mm screw head displacement were also compared. RESULTS The maximal pullout strength in the screws augmented with HA granules was significantly greater compared to those without augmentation (p < 0.05). The augmentation significantly increased the maximal insertion torque of the screws (p < 0.05). Moreover, the number of toggle cycles and the maximal load required to reach 2 mm of displacement were significantly higher in the augmented screws (p < 0.05). CONCLUSION The PPS fixation was significantly enhanced by the augmentation with HA granules in the osteoporotic lumbar spine. The PPS fixation augmented with HA granules might decrease the incidence of screw loosening and implant failure in patients with osteoporotic spine.
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Hong JB, Son DM, Park TH, Woo SH, Lee SJ, Choi UY, Han IB, Chung CK, Kim YJ, Sohn S. Risk of rod fracture according to cross-link position in pedicle subtraction osteotomy (PSO): A finite element study. J Clin Neurosci 2020; 73:304-307. [DOI: 10.1016/j.jocn.2020.01.053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 01/11/2020] [Indexed: 10/25/2022]
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Gaume M, Persohn S, Vergari C, Glorion C, Skalli W, Miladi L. Biomechanical cadaver study of proximal fixation in a minimally invasive bipolar construct. Spine Deform 2020; 8:33-38. [PMID: 31925759 DOI: 10.1007/s43390-019-00014-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 09/14/2019] [Indexed: 12/27/2022]
Abstract
STUDY DESIGN Biomechanical human cadaver study. OBJECTIVE To determine the three-dimensional intervertebral ranges of motion (ROMs) of intact and hook-instrumented thoracic spine specimens subjected to physiological loads, using an in vitro experimental protocol with EOS biplane radiography. Pedicle screws are commonly used in thoracic instrumentation constructs, and their biomechanical properties have been widely studied. Promising clinical results have been reported using a T1-T5 thoracic hook-claw construct for proximal rod anchoring. Instrumentation stability is a crucial factor in minimizing mechanical complications rates but had not been assessed for this construct in a biomechanical study. METHODS Six fresh-frozen human cadaver C6-T7 thoracic spines were studied. The first thoracic vertebrae were instrumented using two claws of supra-laminar and pedicle hooks, each fixed on two adjacent vertebrae, on either side of a single free vertebra. Quasi-static pure-moment loads up to 5 Nm were applied to each specimen before and after instrumentation, in flexion-extension, right and left bending, and axial rotation. Five steel beads impacted in each vertebra allowed 3D tracking of vertebral movements on EOS biplanar radiographs acquired after each loading step. The relative ranges of motion (ROMs) of each pair of vertebras were computed. RESULTS Mean ROMs with the intact specimens were 17° in flexion-extension, 27.9° in lateral bending, and 29.5° in axial rotation. Corresponding values with the instrumented specimens were 0.9°, 2.6°, and 7.3°, respectively. Instrumentation significantly (P < 0.05) decreased flexion-extension (by 92-98%), lateral bending (by 87-96%), and axial rotation (by 68-84%). CONCLUSION This study establishes the biomechanical stability of a double claw-hook construct in the upper thoracic spine, which may well explain the low mechanical complication rate in previous clinical studies. LEVEL OF EVIDENCE Not applicable, experimental cadaver study.
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Affiliation(s)
- M Gaume
- Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 Bd. de l'Hôpital, 75013, Paris, France. .,Pediatrics Orthopedics Department, Necker Hospital, Paris Descartes University, Assistance Publique Hôpitaux de Paris, Paris, France.
| | - S Persohn
- Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 Bd. de l'Hôpital, 75013, Paris, France
| | - C Vergari
- Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 Bd. de l'Hôpital, 75013, Paris, France
| | - C Glorion
- Pediatrics Orthopedics Department, Necker Hospital, Paris Descartes University, Assistance Publique Hôpitaux de Paris, Paris, France
| | - W Skalli
- Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 Bd. de l'Hôpital, 75013, Paris, France
| | - L Miladi
- Pediatrics Orthopedics Department, Necker Hospital, Paris Descartes University, Assistance Publique Hôpitaux de Paris, Paris, France
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Wang HW, Yin YH, Li T, Yu XG, Qiao GY. Effects of transverse connector on reduction and fixation of atlantoaxial dislocation and basilar invagination using posterior C1-C2 screw-rod technique. Spine J 2019; 19:1995-2002. [PMID: 31254651 DOI: 10.1016/j.spinee.2019.06.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 06/21/2019] [Accepted: 06/24/2019] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT The mechanical strength provided by internal fixation is crucial for maintaining reduction and facilitating bony fusion. Though satisfactory results with the C1-C2 technique have been acquired in most clinical reports, the related problems of fusion delay and pseudarthrosis still exist. To increase the chance of bony fusion, a transverse connector (TC) is frequently used to augment torsional stiffness of thoracolumbar screw/rod constructs. Nevertheless, the clinical implication of TC in the management of atlantoaxial dislocation (AAD) and basilar invagination (BI) remains largely unknown. PURPOSE To evaluate the effects of TC application on C1-C2 screw-rod constructs based on consecutive adult patients with AAD and BI in a single institution over a 10-year period. STUDY DESIGN A retrospective study. PATIENT SAMPLE Patients with AAD and BI, who were treated with posterior C1-C2 screw-rod technique with or without TC usage from June 2007 to June 2017 at a single institution. OUTCOME MEASURES The radiological measurements included the anterior atlantodental interval (AADI), posterior atlantodental interval (PADI), height of odontoid process above Chamberlain line, and cervicomedullary angle (CMA). Patients' neurologic status was evaluated with the Japanese Orthopaedic Association (JOA) score. Fusion status was evaluated at different follow-up periods. METHODS We compared the difference of clinical, radiological, and surgical outcomes between the TC and NTC groups postoperatively. RESULTS In total, there were 149 consecutive patients in the TC group and 168 patients in the NTC group. On average, 1.2 TCs per patient were used in the TC group. No significant differences were identified for operative time and blood loss between groups. There was also no statistical difference in the radiological measurements of AADI, PADI, Chamberlain line, and CMA between the TC and NTC groups preoperatively and postoperatively. A significantly higher JOA score was obtained in the TC group than that in the NTC group postoperatively. The fusion rates were higher in the TC group than those in the NCT group at the early stage postoperatively (3 and 6 months; p<.01). CONCLUSIONS Use of TCs seems to improve bony fusion and neurologic outcomes in the treatment of AAD and BI with C1-C2 screw-rod technique.
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Affiliation(s)
- Hua-Wei Wang
- Department of Neurosurgery, PLA General Hospital, 28 Fuxing Rd, Haidian District, Beijing 100853, China
| | - Yi-Heng Yin
- Department of Neurosurgery, PLA General Hospital, 28 Fuxing Rd, Haidian District, Beijing 100853, China
| | - Teng Li
- Department of Neurosurgery, PLA General Hospital, 28 Fuxing Rd, Haidian District, Beijing 100853, China
| | - Xin-Guang Yu
- Department of Neurosurgery, PLA General Hospital, 28 Fuxing Rd, Haidian District, Beijing 100853, China.
| | - Guang-Yu Qiao
- Department of Neurosurgery, PLA General Hospital, 28 Fuxing Rd, Haidian District, Beijing 100853, China
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Obeidat M, Tan Z, Finkelstein JA. Cortical Bone Trajectory Screws for Fixation Across the Cervicothoracic Junction: Surgical Technique and Outcomes. Global Spine J 2019; 9:859-865. [PMID: 31819852 PMCID: PMC6882086 DOI: 10.1177/2192568219838822] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
STUDY DESIGN Clinical case series describing a novel surgical technique. OBJECTIVE Stabilization across the cervicothoracic junction (CTJ) poses technical difficulties which make this procedure challenging. The transition from cervical lordosis to thoracic kyphosis and the orientation of the lateral masses of the cervical spine compared with the pedicles of the thoracic spine create the need to accommodate for 2 planes of alignment when placing instrumentation. A novel surgical technique for instrumentation across the cervicothoracic junction is described. METHODS The use of cortical bone trajectory (CBT) technique for pedicle fixation in the upper thoracic spine is described in combination with cervical lateral mass or pedicle screws. The application in our first 12 patients for stabilization across the CTJ is described. Two case presentations illustrate the technique. RESULTS All the patients had rod screw constructs without the need to skip levels, there was no requirement for transverse connectors and only 1 plane of contouring was required. CONCLUSIONS The use of CBT technique has not been described for the upper thoracic spine. This technique avoids many technical problems associated with posterior instrumentation of the CTJ. The facility of their use in this application arises from the similar coronal plane entry points as the cervical lateral mass screws compared with the more lateral starting point of traditional thoracic pedicle screws. The technique has clinical equipoise to traditional thoracic pedicle screw insertion but with the benefits of an easier ability to perform the instrumentation and saving levels of fusion.
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Affiliation(s)
- Mohammad Obeidat
- Sunnybrook Health Sciences Center, Toronto, Ontario, Canada,University of Toronto, Toronto, Ontario, Canada
| | - Zachary Tan
- Sunnybrook Health Sciences Center, Toronto, Ontario, Canada,University of Toronto, Toronto, Ontario, Canada
| | - Joel A. Finkelstein
- Sunnybrook Health Sciences Center, Toronto, Ontario, Canada,University of Toronto, Toronto, Ontario, Canada,Joel A. Finkelstein, Feldberg Chair in Spinal Research Division of Orthopaedic Surgery, Sunnybrook Health Sciences Center, 2075 Bayview Avenue, Room MG361, Toronto, Ontario, M4N 3M5, Canada.
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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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Biomechanical Analysis of a Growing Rod with Sliding Pedicle Screw System for Early-Onset Scoliosis. JOURNAL OF HEALTHCARE ENGINEERING 2019; 2019:9535070. [PMID: 31281619 PMCID: PMC6594281 DOI: 10.1155/2019/9535070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 03/25/2019] [Indexed: 01/21/2023]
Abstract
Early-onset scoliosis (EOS) remains a challenging condition for which current nonfusion surgeries require iterative lengthening surgeries. A growing rod with sliding pedicle screw system (GRSPSS) was developed to treat spinal deformities without repeated operative lengthening. This study was performed to evaluate whether GRSPSS had similar stability as a conventional pedicle screw system to maintain deformity correction. A serial-linkage robotic manipulator with a six-axis load cell positioned on the end-effector was utilized to evaluate the mechanical stability of the GRSPSS versus conventional fixed scoliosis instrumentation. Ten skeletally mature thoracic female Katahdin sheep spines (T4-L1) were subjected to 2.5 Nm of flexion-extension (FE), lateral bending (LB), and axial rotation (AR) in 2° increments for each state. The overall range of motion (ROM), apical segment ROM, and stiffness were calculated and reported. A two-tailed paired t-test was used to detect significant differences (p < 0.05) between the fixed group and GRSPSS fixation. There were no significant differences in overall range of motion (ROM), apical segment ROM, or stiffness for FE or LB between the GRSPSS group and fixed group. In AR, the GRSPSS group showed increased ROM compared to the fixed group for the overall spine (36.0° versus 19.2°, p < 0.01) and for the instrumented T8-T10 segments (7.0° versus 2.9°, p=0.02). Similarly, the fixed rod elastic zone (EZ) stiffness was significantly greater than the GRSPSS EZ stiffness (0.29 N/m versus 0.17 N/m, p < 0.001). The space around the rod allows for the increased AR observed with the GRSPSS fusion technique and is necessary for axial growth. The GRSPSS fusion model shows equivalent flexion and LB stability to current fusion models and represents a stable fusion technique and may allow for longitudinal growth during childhood.
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Hill G, Nagaraja S, Bridges A, Vosoughi AS, Goel VK, Dreher ML. Mechanical performance of traditional distraction-based dual growing rod constructs. Spine J 2019; 19:744-754. [PMID: 30219359 DOI: 10.1016/j.spinee.2018.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/31/2018] [Accepted: 09/05/2018] [Indexed: 02/03/2023]
Abstract
BACKGROUND Growing rod constructs are an important contribution in the treatment of children with early onset scoliosis even though these devices experience high rates of rod fracture. The mechanical performance of traditional, distraction-based dual growing rod constructs is not well understood, and mechanical models for predicting device performance are limited. PURPOSE Two mechanical models were developed and used to determine the mechanical performance of various growing rod configurations by increasing construct complexity. STUDY DESIGN/SETTING Mechanical bench testing and finite element (FE) analysis. METHODS Static and dynamic compression bending tests were based on an ASTM F1717 method modified to accommodate dual growing rod constructs. Six construct configurations were tested, mechanical properties were recorded, and statistical analyses were performed to determine significant differences between groups: (1) no connectors (rods only), (2) side-by-side connectors, (3) side-by-side connectors plus 4 crosslinks, (4) (40-mm long tandem connectors, (5) 80-mm long tandem connectors, and (6) 80-mm long tandem connectors plus 4 crosslinks. FE analysis was used to predict the stress distribution within the constructs. RESULTS The static results indicated greater stiffness, yield load, and peak load as the axial connector length increased (side-by-side to 40 mm tandem to 80 mm tandem). The dynamic results showed similar cycles to failure for side-by-side and tandem connector (40 and 80 mm) construct configurations without crosslinks. Crosslinks shifted the location of rod fracture observed experimentally and significantly reduced the fatigue life of the construct. The flexibility of the construct decreased significantly as the axial connector length increased. FE predictions were highly consistent with the experimentally measured values and provided information on stress distribution within the rod for comparison to experimental fracture locations. CONCLUSIONS This is the first study to evaluate mechanical performance of various configurations of pediatric growing rod constructs using preclinical models. The current study is consistent with a previous retrieval study in that rigid constructs lacking flexibility (ie, higher stiffness and lower displacement), such as those with 80-mm tandem connectors and multiple crosslinks, demonstrated decreased mechanical performance as shown through both experimental and computational models. Additionally, the experimental and computational findings suggest that surgeons should strategically consider the number of interconnecting components and subsequent stress concentrations along the posterior side of the rod. For example, changing the placement of crosslinks to low stress regions of the construct or not using crosslinks in the construct are options.
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Affiliation(s)
- Genevieve Hill
- U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA; University of Maryland, College Park, College Park, MD 20742.
| | - Srinidhi Nagaraja
- U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
| | - Austin Bridges
- U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
| | - Ardalan Seyed Vosoughi
- Engineering Center for Orthopaedic Research Excellence, Department of Bioengineering and Orthopaedic Surgery, Colleges of Engineering and Medicine, University of Toledo, Toledo, OH, 43606, USA
| | - Vijay K Goel
- Engineering Center for Orthopaedic Research Excellence, Department of Bioengineering and Orthopaedic Surgery, Colleges of Engineering and Medicine, University of Toledo, Toledo, OH, 43606, USA
| | - Maureen L Dreher
- U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
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Wang T, Cai Z, Zhao Y, Wang W, Zheng G, Wang Z, Wang Y. The Influence of Cross-Links on Long-Segment Instrumentation Following Spinal Osteotomy: A Finite Element Analysis. World Neurosurg 2018; 123:e294-e302. [PMID: 30496922 DOI: 10.1016/j.wneu.2018.11.154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 11/16/2018] [Accepted: 11/18/2018] [Indexed: 10/27/2022]
Abstract
OBJECTIVE To develop finite element models of spine following osteotomy and evaluate the effect of number and location of cross-links (CLs) on long-segment instrumentation. METHODS A finite element model of instrumented spine following osteotomy was created from computed tomography images of a postoperative male patient with thoracolumbar kyphotic deformity. Five fixation models were established to simulate different number and location of CLs. Four loading conditions (flexion, extension, lateral bending, and axial rotation) were applied on the models. Range of motion (ROM), maximum value and distribution of stress on implants, and stress on vertebrae were compared between models. RESULTS With increased number of CLs, average ROM of instrumented segments was reduced by 2.37%, 1.89%, and 2.49% in flexion, extension, and lateral bending. ROM was reduced by 21.98% in loading axial rotation condition. With increased number of CLs, ROM tended to be limited. Peak stresses were located on rods during axial rotation, on proximal pedicle screws during flexion, and on the osteotomy site during extension and lateral bending. CLs had an effect of dispersing stress concentration. CONCLUSIONS The application of CLs enhanced the rigidity of the construct. With increased number of CLs, ROM of the construct was decreased, especially in axial rotation. CLs can also disperse the stress concentration. After comparing various CL configurations in different motion conditions, we believe that the optimal method is to place 2 CLs at the osteotomy site and the proximal segment.
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Affiliation(s)
- Tianhao Wang
- Department of Orthopaedics, Southwest Hospital, Third Military Medical University, Chongqing, China; Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China
| | - Zhihua Cai
- School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan, China
| | - Yongfei Zhao
- Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China
| | - Wei Wang
- School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan, China
| | - Guoquan Zheng
- Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China
| | - Zheng Wang
- Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China
| | - Yan Wang
- Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China.
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Godzik J, Hool N, Dalton JF, Whiting AC, Newcomb AGUS, Kelly BP, Crawford NR. Impact of Connector Placement and Design on Bending Stiffness of Spinal Constructs. World Neurosurg 2018; 121:e89-e95. [PMID: 30217782 DOI: 10.1016/j.wneu.2018.08.235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/29/2018] [Accepted: 08/31/2018] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To evaluate the stability of multiple rod-connector construct designs using a mechanical 4-point bending testing frame. METHODS A mechanical study was used to evaluate the bending stiffness of 3 connectors across 12 different configurations of rod-connector-rod constructs. Stability was evaluated in flexion-extension and lateral bending. Combinations of rods having 1 of 3 diameters (4.0 mm, 5.5 mm, and 6.0 mm) connected by 1 of 3 connector types (parallel open, snap-on, and hinged) were compared. Configurations with single connectors and with double connectors with variable spacing were also compared to simulate revision surgery conditions. RESULTS Constructs consisting of 4.0-mm rods connected to 4.0-mm rods were significantly less stiff as the total number of connectors used in a series exceeded 2. When single-connector configurations were compared, parallel open rod connectors demonstrated greater stiffness in flexion-extension than hinged open connectors, whereas hinged open connectors demonstrated greater stiffness in lateral bending. Using double connectors increased stiffness of 4.0- to 4.0-mm rod configurations in flexion-extension and lateral bending, 4.0- to 6.0-mm rod configurations in flexion-extension, and 5.5- to 6.0-mm rod configurations in lateral bending. Spacing the double connectors significantly improved lateral bending stiffness of 4.0- to 4.0-mm and 5.5- to 6.0-mm rod configurations. CONCLUSIONS Our data indicate that the design, number, and placement of rod connectors have a significant impact on the bending stiffness of a surgical construct. Such mechanical data may influence construct design in primary and revision surgeries of the cervical spine and cervicothoracic junction.
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Affiliation(s)
- Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Nick Hool
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | - Alexander C Whiting
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Anna G U S Newcomb
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.
| | - Neil R Crawford
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Advantages of an on-the-screwhead crosslink connector for atlantoaxial fixation using the Goel/Harms technique. J Clin Neurosci 2018; 50:183-189. [DOI: 10.1016/j.jocn.2018.01.043] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 01/08/2018] [Indexed: 11/20/2022]
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Lee MC, Jarvis C, Solomito MJ, Thomson JD. Comparison of S2-Alar and traditional iliac screw pelvic fixation for pediatric neuromuscular deformity. Spine J 2018; 18:648-654. [PMID: 28870838 DOI: 10.1016/j.spinee.2017.08.253] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 07/27/2017] [Accepted: 08/29/2017] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Many pelvic fixation options exist for posterior spinal fusion of pediatric neuromuscular scoliosis, including standard iliac screws (SISs) or a more recently introduced S2-Alar (S2A) technique. However, little data exist comparing the clinical and radiographic outcomes of these techniques. PURPOSE This study aimed to dentify differences in clinical and radiographic outcomes for pediatric neuromuscular scoliosis patients treated with SIS or S2A pelvic fixation. STUDY DESIGN/SETTING This was a retrospective cohort study at a pediatric orthopedic clinic. PATIENT SAMPLE Patients aged 8-19 years undergoing posterior spinal fusion to the pelvis for neuromuscular scoliosis using SIS or S2A technique, with Gross Motor Function Classification System (GMFCS) Level 4 or 5 were included. OUTCOMES MEASURES Postoperative complication rates associated with pelvic fixation method were the outcome measures. METHODS Charts and radiographs were reviewed for demographics, intra- and postoperative course, levels of instrumentation, operative correction, and implant failure (IF). Postoperative complications were classified according to the Accordion scale. RESULTS We studied 50 patients (28 SIS, 22 S2A) aged 14.0±2.8 years and an average follow-up of 3.5±1.7 years. The average number of levels fused was 16.5±1.1 with an average curve correction of 48°±21° postoperatively. A significant difference in radiographic IF rates was noted between SIS and S2A groups (57% vs. 27%, p=.02). No difference was noted between groups for frequency or severity of postoperative complications, inclusive of wound infections. Subgroup analysis demonstrated equivalent IF rates when comparing the S2A group with the SIS group with cross-links. CONCLUSIONS The S2A group generally demonstrated improved rates of radiographic IF compared with the SIS group, but the rates became equivalent when a cross-link was added to an SIS construct. Further, no difference in postoperative complication rates were identified between SIS and S2A groups.
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Affiliation(s)
- Mark C Lee
- Connecticut Children's Medical Center, 282 Washington St, Hartford, CT 06106.
| | - Casey Jarvis
- University of Connecticut, 375 Astor Drive, Sayville, NY 11782
| | - Matthew J Solomito
- Connecticut Children's Medical Center, 399 Farmington Ave, Farmington, CT 06106
| | - Jeffrey D Thomson
- Connecticut Children's Medical Center, 282 Washington St, Hartford, CT 06106
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Borkowski SL, Tamrazian E, Bowen RE, Scaduto AA, Ebramzadeh E, Sangiorgio SN. Challenging the Conventional Standard for Thoracic Spine Range of Motion: A Systematic Review. JBJS Rev 2018; 4:e51-e511. [PMID: 27487429 DOI: 10.2106/jbjs.rvw.o.00048] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Segmental motion is a fundamental characteristic of the thoracic spine; however, studies of segmental ranges of motion have not been summarized or analyzed. The purpose of the present study was to present a summary of the literature on intact cadaveric thoracic spine segmental range of motion in each anatomical plane. METHODS A systematic MEDLINE search was performed with use of the terms "thoracic spine," "motion," and "cadaver." Reports that included data on the range of motion of intact thoracic human cadaveric spines were included. Independent variables included experimental details (e.g., specimen age), type of loading (e.g., pure moments), and applied moment. Dependent variables included the ranges of motion in flexion-extension, lateral bending, and axial rotation. RESULTS Thirty-three unique articles were identified and included. Twenty-three applied pure moments to thoracic spine specimens, with applied moments ranging from 1.5 to 8 Nm. Estimated segmental range of motion pooled means ranged from 1.9° to 3.8° in flexion-extension, from 2.1° to 4.4° in lateral bending, and from 2.4° to 5.2° in axial rotation. The sums of the range of motion pooled means (T1 to T12) were 28° in flexion-extension, 36° in lateral bending, and 45° in axial rotation. CONCLUSIONS The pooled ranges of motion were similar to reported in vivo motions but were considerably smaller in magnitude than the frequently referenced values reported prior to the widespread use of biomechanical testing standards. Improved reporting of biomechanical testing methods, as well as specimen health, may be beneficial for improving on these estimations of segmental cadaveric thoracic spine range of motion.
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Affiliation(s)
- Sean L Borkowski
- The J. Vernon Luck, Sr., M.D. Orthopaedic Research Center, Orthopaedic Institute for Children, University of California, Los Angeles, Los Angeles, California.,Lucideon, Schenectady, New York
| | | | - Richard E Bowen
- Orthopaedic Institute for Children and Department of Orthopaedic Surgery, University of California, Los Angeles, Los Angeles, California
| | - Anthony A Scaduto
- Orthopaedic Institute for Children and Department of Orthopaedic Surgery, University of California, Los Angeles, Los Angeles, California
| | - Edward Ebramzadeh
- The J. Vernon Luck, Sr., M.D. Orthopaedic Research Center, Orthopaedic Institute for Children, University of California, Los Angeles, Los Angeles, California
| | - Sophia N Sangiorgio
- The J. Vernon Luck, Sr., M.D. Orthopaedic Research Center, Orthopaedic Institute for Children, University of California, Los Angeles, Los Angeles, California
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Hill G, Nagaraja S, Akbarnia BA, Pawelek J, Sponseller P, Sturm P, Emans J, Bonangelino P, Cockrum J, Kane W, Dreher M. Retrieval and clinical analysis of distraction-based dual growing rod constructs for early-onset scoliosis. Spine J 2017; 17:1506-1518. [PMID: 28456673 DOI: 10.1016/j.spinee.2017.04.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 03/15/2017] [Accepted: 04/21/2017] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Growing rod constructs are an important contribution for treating patients with early-onset scoliosis. These devices experience high failure rates, including rod fractures. PURPOSE The objective of this study was to identify the failure mechanism of retrieved growing rods, and to identify differences between patients with failed and intact constructs. STUDY DESIGN/SETTING Growing rod patients who had implant removal and were previously enrolled in a multicenter registry were eligible for this study. PATIENT SAMPLE Forty dual-rod constructs were retrieved from 36 patients across four centers, and 34 of those constructs met the inclusion criteria. Eighteen constructs failed due to rod fracture. Sixteen intact constructs were removed due to final fusion (n=7), implant exchange (n=5), infection (n=2), or implant prominence (n=2). OUTCOME MEASURES Analyses of clinical registry data, radiographs, and retrievals were the outcome measures. METHODS Retrievals were analyzed with microscopic imaging (optical and scanning electron microscopy) for areas of mechanical failure, damage, and corrosion. Failure analyses were conducted on the fracture surfaces to identify failure mechanism(s). Statistical analyses were performed to determine significant differences between the failed and intact groups. RESULTS The failed rods fractured due to bending fatigue under flexion motion. Construct configuration and loading dictate high bending stresses at three distinct locations along the construct: (1) mid-construct, (2) adjacent to the tandem connector, or (3) adjacent to the distal anchor foundation. In addition, high torques used to insert set screws may create an initiation point for fatigue. Syndromic scoliosis, prior rod fractures, increase in patient weight, and rigid constructs consisting of tandem connectors and multiple crosslinks were associated with failure. CONCLUSION This is the first study to examine retrieved, failed growing rod implants across multiple centers. Our analysis found that rod fractures are due to bending fatigue, and that stress concentrations play an important role in rod fractures. Recommendations are made on surgical techniques, such as the use of torque-limiting wrenches or not exceeding the prescribed torques. Additional recommendations include frequent rod replacement in select patients during scheduled surgeries.
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Affiliation(s)
- Genevieve Hill
- US Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA; Fischell Department of Bioengineering, University of Maryland, Room 2330, Jeong H. Kim Engineering Building, Bldg #225, College Park, MD 20742, USA.
| | - Srinidhi Nagaraja
- US Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA; Fischell Department of Bioengineering, University of Maryland, Room 2330, Jeong H. Kim Engineering Building, Bldg #225, College Park, MD 20742, USA
| | - Behrooz A Akbarnia
- Growing Spine Study Group, 6190 Cornerstone Ct East, Suite 212, San Diego, CA 92121, USA
| | - Jeff Pawelek
- Growing Spine Study Group, 6190 Cornerstone Ct East, Suite 212, San Diego, CA 92121, USA
| | - Paul Sponseller
- Growing Spine Study Group, 6190 Cornerstone Ct East, Suite 212, San Diego, CA 92121, USA; Johns Hopkins Hospital, 1800 Orleans St, Baltimore, MD 21287, USA
| | - Peter Sturm
- Growing Spine Study Group, 6190 Cornerstone Ct East, Suite 212, San Diego, CA 92121, USA; Cincinnati Children's Hospital, 3333 Burnet Ave, MLC 2017, Cincinnati, OH 45229, USA
| | - John Emans
- Growing Spine Study Group, 6190 Cornerstone Ct East, Suite 212, San Diego, CA 92121, USA; Boston Children's Hospital, 300 Longwood Ave, Boston, MA 02115, USA
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- Growing Spine Study Group, 555 East Wells St, Suite 1100, Milwaukee, WI 53202, USA
| | - Pablo Bonangelino
- US Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Joshua Cockrum
- US Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - William Kane
- Exponent, Inc., 3440 Market St, Suite 600, Philadelphia, PA 19104, USA
| | - Maureen Dreher
- US Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA; Fischell Department of Bioengineering, University of Maryland, Room 2330, Jeong H. Kim Engineering Building, Bldg #225, College Park, MD 20742, USA
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Abstract
STUDY DESIGN Biomechanical study of double-level pedicle screw constructs with or without crosslinks (CL) in an unstable model. OBJECTIVES The purpose of this study is to investigate the optimal position and orientation of the CL. SUMMARY OF BACKGROUND DATA Several reports have described biomechanical research on such CL, but no definite consensus has been reached regarding the effects. Very few studies have examined the position and orientation of the CL. The question of where and how the CL should be clinically set remains unanswered. METHODS Ten cadaveric lumbar spines (L3-L5) of boars were used and 7 models were prepared by the sequential damage and spinal instrumentation of each specimen. Bending stiffness was measured in flexion, extension, lateral bending, and axial rotation for each model using 6-axis material tester under torque of 0 to ±3 N m. Results for each configuration were compared using analysis of variance and the Turkey-Kramer test. RESULTS In flexion, extension, and lateral bending, 7 models showed similar stiffness with no significant differences. In axial rotation, stiffness increased significantly (P<0.05) in the cephalic, central, caudal, and oblique CL models in comparison with that of the no CL model, and stiffness of the horizontal 2 CL and oblique 2 CL models was significantly higher than that of cephalic, central, caudal, and oblique CL models (P<0.05). However, no significant differences in stiffness were seen between cephalic, central, and caudal CL models, between the central and oblique CL models, or between the horizontal and oblique 2 CL models. CONCLUSIONS Concomitant use of CLs significantly increased axial rotational stiffness, even though stiffness in flexion, extension, and lateral bending was not increased. In addition, stiffness in axial rotation significantly improved with the use of 2 CLs instead of a single CL, and stiffness was unchanged by position and orientation of CL.
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Does Lumbopelvic Fixation Add Stability? A Cadaveric Biomechanical Analysis of an Unstable Pelvic Fracture Model. J Orthop Trauma 2017; 31:37-46. [PMID: 27997465 DOI: 10.1097/bot.0000000000000703] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE We sought to determine the role of lumbopelvic fixation (LPF) in the treatment of zone II sacral fractures with varying levels of sacral comminution combined with anterior pelvic ring (PR) instability. We also sought to determine the proximal extent of LPF necessary for adequate stabilization and the role of LPF in complex sacral fractures when only 1 transiliac-transsacral (TI-TS) screw is feasible. MATERIALS AND METHODS Fifteen L4 to pelvis fresh-frozen cadaveric specimens were tested intact in flexion-extension (FE) and axial rotation (AR) in a bilateral stance gliding hip model. Two comminution severities were simulated through the sacral foramen using an oscillating saw, with either a single vertical fracture (small gap, 1 mm) or 2 vertical fractures 10 mm apart with the intermediary bone removed (large gap). We assessed sacral fracture zone (SZ), PR, and total lumbopelvic (TL) stability during FE and AR. The following variables were tested: (1) presence of transverse cross-connector, (2) presence of anterior plate, (3) extent of LPF (L4 vs. L5), (4) fracture gap size (small vs. large), (5) number of TI-TS screws (1 vs. 2). RESULTS The transverse cross-connector and anterior plate significantly increased PR stability during AR (P = 0.02 and P = 0.01, respectively). Increased sacral comminution significantly affected SZ stability during FE (P = 0.01). Two versus 1 TI-TS screw in a large-gap model significantly affected TL stability (P = 0.04) and trended toward increased SZ stabilization during FE (P = 0.08). Addition of LPF (L4 and L5) significantly improved SZ and TL stability during AR and FE (P < 0.05). LPF in combination with TI-TS screws resulted in the least amount of motion across all 3 zones (SZ, PR, and TL) compared with all other constructs in both small-gap and large-gap models. CONCLUSIONS The role of LPF in the treatment of complex sacral fractures is supported, especially in the setting of sacral comminution. LPF with proximal fixation at L4 in a hybrid approach might be needed in highly comminuted cases and when only 1 TI-TS screw is feasible to obtain maximum biomechanical support across the fracture zone.
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Biomechanical stability of transverse connectors in the setting of a thoracic pedicle subtraction osteotomy. Spine J 2015; 15:1629-35. [PMID: 25771755 DOI: 10.1016/j.spinee.2015.03.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 12/19/2014] [Accepted: 03/07/2015] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Transverse connectors (TCs) are often used to improve the rigidity of posterior spinal instrumentation as previous investigations have suggested that TCs enhance torsional rigidity in long-segment thoracic constructs. Posterior osteotomies, such as pedicle subtraction osteotomy (PSO), are used in severe thoracic deformities and provide a significant amount of correction; as a consequence, however, PSOs also induce three-column spinal instability. In theory, augmentation of longitudinal constructs with TC after a thoracic PSO may provide additional rigidity, but the concept has not been previously evaluated. PURPOSE To evaluate the biomechanical contribution of TC to the rigidity of a long-segment pedicle screw-rod construct after a thoracic PSO. STUDY DESIGN An in vitro fresh-frozen human cadaveric biomechanical analysis. METHODS Seven human cadaveric thoracic spines were prepared and instrumented from T4-T10 with bilateral pedicle screws/rods and a PSO was performed at T7. Intact range of motion (ROM) testing was performed with nondestructive loading and analyzed by loading modality (axial rotation [AR], flexion/extension [FE], and lateral bending [LB]). Range of motion analysis was performed in the unaugmented construct, the construct augmented with one TC, and the construct augmented with two TCs. RESULTS After PSO and an unaugmented longitudinal pedicle screw-rod construct, T4-T10 (overall construct) and T6-T8 (PSO site) ROMs were significantly reduced in all planes of motion compared with intact condition (AR: 11.8° vs. 31.7°; FE: 2.4° vs. 12.3°; 3.4° vs. 17.9°, respectively, p<.05). Augmentation of longitudinal construct with either one or two TCs did not significantly increase construct rigidity in FE or LB compared with the unaugmented construct (p>.05). In contrast, during AR, global ROM was significantly reduced by 43% and 48% at T6-T8 (1.7° and 1.2° vs. 2.38°, respectively) after addition of one and two TCs (p<.05), respectively. One TC did not significantly reduce torsional ROM from the intact state. CONCLUSIONS Two TCs significantly improved torsional rigidity of the entire construct and at the PSO site, with no differences in rigidity for FE and LB or with the addition of only one TC. In the setting of a PSO and long-segment pedicle screw-rod construct, augmentation with at least two TCs should be considered to improve torsional rigidity.
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Garg S, Niswander C, Pan Z, Erickson M. Cross-Links Do Not Improve Clinical or Radiographic Outcomes of Posterior Spinal Fusion With Pedicle Screws in Adolescent Idiopathic Scoliosis: A Multicenter Cohort Study. Spine Deform 2015; 3:338-344. [PMID: 27927479 DOI: 10.1016/j.jspd.2014.12.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 11/17/2014] [Accepted: 12/14/2014] [Indexed: 11/25/2022]
Abstract
STUDY DESIGN Retrospective, comparative analysis. OBJECTIVES Comparative analysis was performed to determine the differences, if any, between adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF) with and without cross-links. SUMMARY OF BACKGROUND DATA Cross-links are frequently used during PSF for AIS. It is unclear whether they provide any advantage for patients with all-pedicle screw constructs. METHODS A prospectively collected multicenter database of patients with AIS undergoing spinal fusion was retrospectively queried. Study inclusion criteria were primary PSF with all-pedicle screw fixation (greater than 90% fixation points) and minimum 2 years' follow-up. Collected data included demographics, radiographic measures, complications, Scoliosis Research Society-22r and Spinal Appearance Questionnaire (SAQ) scores. RESULTS A total of 500 patients were included (377 cross-link and 123 non-cross-link). Age, body mass index, gender, and preoperative major Cobb angle were not different between groups. Except for a slightly decreased lumbar Cobb angle (2.7°) in the cross-link group, no other radiographic measures were different at follow-up. Complications were not significantly different between groups: 21 of 377 (6%) crosslink and 9 of 123 (7%) non-cross-link. Infection occurred in 1 patient in the cross-link group and none in the non-cross link group. Reoperation occurred in 4 patients, all with cross-links (3 for implant removal and 1 for distal adding-on). Scoliosis Research Society-22r scores, total and individual domains, improved by a similar amount in both groups. At follow-up, parent and patient SAQ appearance scores were not significantly different. The SAQ expectations domain scores were similar for all visits and improved for both patients and parents. CONCLUSIONS There do not appear to be significant clinical or radiographic outcome differences in patients with AIS undergoing PSF based on the use of cross-links at 2-year follow-up. Surgeons should consider eliminating cross-links in patients with AIS who have PSF with all-pedicle screw constructs. This may have substantial cost savings without affecting patient outcome.
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Affiliation(s)
- Sumeet Garg
- Children's Hospital Colorado Orthopedics Institute, University of Colorado, 13123 East 16th Avenue, Box 060, Aurora, CO 80045, USA.
| | - Cameron Niswander
- Children's Hospital Colorado Orthopedics Institute, University of Colorado, 13123 East 16th Avenue, Box 060, Aurora, CO 80045, USA
| | - Zhaoxing Pan
- Children's Hospital Colorado Orthopedics Institute, University of Colorado, 13123 East 16th Avenue, Box 060, Aurora, CO 80045, USA
| | - Mark Erickson
- Children's Hospital Colorado Orthopedics Institute, University of Colorado, 13123 East 16th Avenue, Box 060, Aurora, CO 80045, USA
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Radcliff KE, Hussain MM, Moldavsky M, Klocke NF, Vaccaro A, Albert TJ, Khalil S, Bucklen BS. Stabilization of the craniocervical junction after an internal dislocation injury: an in vitro study. Spine J 2015; 15:1070-6. [PMID: 25681231 DOI: 10.1016/j.spinee.2015.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/22/2014] [Accepted: 02/01/2015] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Reconstructive surgeries at the occipitocervical (OC) junction have been studied in treating degenerative conditions. There is a paucity of data for optimal fixation for a traumatically unstable OC joint. In clinical OC dislocations, segmental fixation may be impossible because of vertebral artery injury or fracture. Segmental fixation of the occiput, C1, and C2 demonstrated maximum biomechanical stability in fixation of an unstable craniocervical dislocation. A biomechanical study comparing various points of cervical posterior screw fixation after recreating traumatic injury would illuminate relative advantages between the various techniques. PURPOSE To determine the rigidity lost, if any, of segmental C0-C2 posterior screw fixation versus fixation skipping C1 at the OC junction, with or without a cross-connector. STUDY DESIGN This study is a cadaveric biomechanical investigation. METHODS Intervertebral motions and translations were recorded in seven specimens under conditions in the following order: intact, OC dislocation model with complete disruption of the cruciate ligaments, alar ligaments, and occipitoatlantal/atlantoaxial capsules (injury), segmental posterior fixation (SPF) with posterior instrumentation (ELLIPSE; Globus Medical, Inc., Audubon, PA, USA) at occiput, C1, and C2 levels, endpoint fixation (EPF) with posterior instrumentation at occiput and C1 level skipping C1, and endpoint fixation with a cross-connector (EPFC). Motion was applied through a custom spine simulator with a pure moment load of 2.5 Nm and measured with motion capture markers attached to occiput (C0), anterior C1 ring, and C2. Flexion-extension (FE), lateral bending (LB), axial rotation (AR), and cranial-caudal (CC) motions were recorded in terms of C0-C2. Results were reported as a percentage of injured motion (injury=100%), unless otherwise stated. RESULTS The injury significantly increased the motion to 165%, 263%, and 130%, during FE, LB, and AR, respectively, of intact. The CC translations increased to 164%, 254%, and 121% during FE, LB, AR, respectively, of intact. Segmental posterior fixation significantly reduced motion to 7%, 8%, and 1%, during FE, LB, and AR, respectively, of injury. Endpoint fixation significantly increased motion in FE, resulting in 12%, 6%, and 4% during FE, LB, and AR, respectively, of injury when compared with SPF. The EPFC construct decreased the motion compared with its counterpart to 8.6%, 5.7%, and 3.2% during FE, LB, and AR, respectively. CONCLUSIONS All fixation constructs significantly reduced motion in all loading modes and CC translations, compared with intact and injury. The construct with the greatest stability against craniocervical dislocation included SPF with instrumentation at the occiput, C1, and C2. By skipping C1 using the EPF, FE and cephalad-caudal translations significantly increased compared with posterior fixation at every level. The addition of a cross-connector increased the stability but was not statistically significant.
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Affiliation(s)
- Kris E Radcliff
- Rothman Institute, 2500 English Creek Ave., Building 1300, Egg Harbor Township, NJ 08234, USA
| | - Mir M Hussain
- MERC, Globus Medical, Inc., 2560 General Armistead Ave., Audubon, PA 19403, USA.
| | - Mark Moldavsky
- MERC, Globus Medical, Inc., 2560 General Armistead Ave., Audubon, PA 19403, USA
| | - Noelle F Klocke
- MERC, Globus Medical, Inc., 2560 General Armistead Ave., Audubon, PA 19403, USA
| | - Alexander Vaccaro
- Rothman Institute, 925 Chestnut St, 5th Floor, Philadelphia, PA 19107, USA
| | - Todd J Albert
- Rothman Institute, 925 Chestnut St, 5th Floor, Philadelphia, PA 19107, USA
| | - Saif Khalil
- MERC, Globus Medical, Inc., 2560 General Armistead Ave., Audubon, PA 19403, USA
| | - Brandon S Bucklen
- MERC, Globus Medical, Inc., 2560 General Armistead Ave., Audubon, PA 19403, USA
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Rahmathulla G, Deen HG. Spine fusion cross-link causing delayed dural erosion and CSF leak: case report. J Neurosurg Spine 2015; 22:439-43. [PMID: 25635637 DOI: 10.3171/2014.9.spine14244] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The past 2 decades have seen a considerable increase in the number of lumbar spinal fusion surgeries. To enhance spinal stabilization and fusion, make the construct resistant to or stiffer for axial stress loading, lateral bending, and torsional stresses, cross-links and connectors were designed and included in a rod-screw construct. The authors present the case of a 49-year-old woman who presented 11 years after undergoing an L4-5 decompression and fusion in which a pedicle screw-rod construct with an integrated cross-link was designed to attach onto the pedicle screws. The patient's response at the time to the initial surgery was excellent; however, at the time of presentation 11 years later, she had significant postural headaches, severe neurogenic claudication, and radiculopathy. Imaging revealed canal compression across the instrumented levels and a possible thickened adherent filum terminale. Reexploration of the level revealed a large erosive dural defect with a CSF leak, spinal canal compression, and a thickened filum at the level of the cross-link. To the author's knowledge, such complications have not been reported in literature. The authors discuss this rare complication of spinal fusion and the need to avoid dural compression when cross-links are used.
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Does addition of crosslink to pedicle-screw-based instrumentation impact the development of the spinal canal in children younger than 5 years of age? 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 2014; 24:1391-8. [DOI: 10.1007/s00586-014-3727-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 12/14/2014] [Accepted: 12/14/2014] [Indexed: 11/30/2022]
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Effectiveness of cross-linking posterior segmental instrumentation in adolescent idiopathic scoliosis: a 2-year follow-up comparative study. Spine J 2013; 13:1485-92. [PMID: 23800823 DOI: 10.1016/j.spinee.2013.05.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 02/08/2013] [Accepted: 05/04/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Surgeons continue to debate the need for a cross-link (CL) in posterior spinal instrumentation constructs with segmental pedicle screws in adolescent idiopathic scoliosis (AIS). Advantage of CLs is increased stiffness of the construct, and disadvantages include added expense and risk of late operative-site pain and pseudarthrosis. PURPOSE To compare the effectiveness of using CLs versus using no cross-links (NCLs) in posterior segmental instrumentation in AIS. STUDY DESIGN Retrospective comparative study, level of evidence 3. PATIENT SAMPLE Seventy-five AIS patients less than 21 years of age, who underwent posterior spinal instrumentation with segmental pedicle screws (25 with CLs and 50 with NCLs) at a single institution with 2-year follow-up, are described. OUTCOME MEASURES Physiologic measures include imaging: thoracic and lumbar Cobb angles, correction rate, apical vertebral translation (AVT), and apical vertebral rotation (AVR); self-report measures include Scoliosis Research Society (SRS) domain outcome scores. METHODS Preoperative (pre-op) and postoperative first erect, 1-year, and 2-year follow-up radiographs were measured. Instrumentation-related complications and normalized SRS scores were recorded. Independent sample t test, χ(2) test, and repeated-measures analysis of variance were used for analyses. RESULTS The average age at surgery was 14 years, the mean pre-op Cobb angle was 57°, and the mean number of levels fused was 10.9. The groups were similar preoperatively with respect to age, sex, Lenke curve, Cobb angle, AVT, and Risser grade and were similar intraoperatively for levels fused and anchor density. There was no difference in AVR, Cobb angle, correction rate, or AVT between the groups (p>.05). Complications included one wound infection in the CL group and one painful scar in the NCL group. There were no differences in SRS domain scores. CONCLUSION We observed no differences in maintenance of correction, SRS scores, and complications with or without cross-linking posterior segmental instrumentation in AIS patients over 2-year follow-up. Further follow-up is necessary.
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En bloc vertebral column derotation provides spinal derotation but no additional effect on thoracic rib hump correction as compared with no derotation in adolescents undergoing surgery for idiopathic scoliosis with total pedicle screw instrumentation. Spine (Phila Pa 1976) 2013; 38:1576-83. [PMID: 23680831 DOI: 10.1097/brs.0b013e31829a6d37] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN A comparative review of 2 cohorts with prospective data collection. OBJECTIVE To compare clinical and radiographical parameters in patients with adolescent idiopathic scoliosis undergoing surgery, using total pedicle screw instrumentation with and without en bloc vertebral column derotation (DVR). SUMMARY OF BACKGROUND DATA All pedicle screw instrumentations with or without DVR are an effective surgical method for adolescent idiopathic scoliosis correction. However, there are limited data comparing pedicle screw instrumentation alone with pedicle screws with DVR on clinical and radiographical outcomes. METHODS We followed 72 consecutive children and adolescents (14 males, mean age at surgery: 14.7 [range, 9.0-18.0] years; 6 juveniles, 66 adolescents) operated for a structural thoracic idiopathic scoliosis (Lenke 1-4, or 6) using all pedicle screw construct in a prospective manner for a minimum of 2 years. Of them, 24 had pedicle screw instrumentation with apical monoaxial screws without derotation (N-DVR) and 48 with en bloc DVR. RESULTS Preoperatively, the mean (SD) main thoracic curve was 56° ± 9° and 57° ± 11° and was corrected to 16° ± 6° in both groups at 2-year follow-up (not significant). Thoracic rib hump averaged 12.3° ± 3.6° versus 14.2° ± 5.0° (P = 0.075) preoperatively and 7.2° ± 3.8° versus 8.3° ± 3.7° at 2-year follow-up in the N-DVR and in the DVR both groups, respectively (P = 0.30). Correction of spinal rotation in the main thoracic curve as assessed by the Upsani score was significantly better in the DVR group than in the N-DVR group at 6 months (P = 0.038) and 2-year follow-up (P = 0.039). Thoracic kyphosis reduced from a mean of 23° ± 18° to 20° ± 9° in the N-DVR group but remained unchanged in the DVR group (P = 0.11 between groups at 2-year follow-up). CONCLUSION En bloc DVR has a significant effect on radiographical spinal column derotation and may help prevent flattening of thoracic kyphosis, but this derotation is not reflected by better thoracic rib hump correction at 2-year follow-up. LEVEL OF EVIDENCE 2.
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Abstract
STUDY DESIGN Retrospective study. OBJECTIVE To assess critically if cross-links are necessary adjuvants in posterior spinal constructs. SUMMARY OF BACKGROUND DATA Although numerous biomechanical studies are available in the literature, there has been no clinical study that has evaluated the need for cross-links in clinical situations. METHODS The spinal constructs of patients of varied etiology who underwent surgery between July 2007 and July 2011 without the usage of cross-links were evaluated. The immediate postoperative erect radiographs were compared with the erect radiographs at the last follow-up by 2 independent observers (spine fellows not involved in the management of the patients) critically for any rotational instability using the Nash-Moe technique of assessment of vertebral rotation as well as for any "parallelogram effect." The intraobserver and interobserver reliability was analyzed. RESULTS There were 208 cases included in the study during the study period that satisfied the criteria. The total number of motion segments fused was 707 ranging from 1 to 15 involving various etiologies. The average follow-up was 15 months (12-36 mo). Barring one patient with a thoracolumbar fracture with rotational instability (AO [Arbeitsgemeinschaft für Osteosynthesefragen] type C) who had undergone a short-segment fixation, none of the cases demonstrated any rotational instability in the follow-up radiographs. Interestingly, the rotational instability (parallelogram effect) in that patient got corrected spontaneously once anterior reconstruction was performed. The intraobserver reliability was 100% and the interobserver reliability was 92.83%. This variability was in assessing the grade of vertebral rotation only; none of the levels had a change in rotation irrespective of variation in grade assessment in the final postoperative radiograph. CONCLUSION This study concludes that use of cross-links in clinical practice may be avoidable. The derivations from biomechanical studies do not translate into clinical advantages. Eliminating the usage of cross-links reduces the operative time as well as the overall total hospital costs (a single cross-link may cost anywhere between $1500 and $2000 and surgeons tend to use single or multiple cross-links). Additionally, prominence of implants, corrosion, infection, implant failure, and pseudarthrosis are the other complications attributed to cross-links in the literature that can be eliminated by preventing their incorporation in spinal constructs. LEVEL OF EVIDENCE N/A.
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Gotfryd AO, Avanzi O. Randomized Clinical Study on Surgical Techniques With Different Pedicle Screw Densities in the Treatment of Adolescent Idiopathic Scoliosis Types Lenke 1A and 1B. Spine Deform 2013; 1:272-279. [PMID: 27927358 DOI: 10.1016/j.jspd.2013.05.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 05/10/2013] [Accepted: 05/13/2013] [Indexed: 11/17/2022]
Abstract
STUDY DESIGN Randomized clinical trial. OBJECTIVES To analyze the impact of surgical techniques with different pedicle screw densities on clinical, functional, and radiographic outcomes, and on costs for patients with adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA The use of pedicle screws to correct spinal deformities has grown. However, there is no scientific evidence that higher-density screws offer better results for AIS treatment. METHODS Patients with Lenke 1A/1B AIS and main thoracic curves to the right, 45° to 70°, were operated on using a posterior approach and free-hand technique. Group 1 was treated with 10 screws in strategically determined vertebrae: 4 in the base, 3 in central vertebrae, and 3 in superior vertebrae. In Group 2, the principles of segmental instrumentation were followed, treating all pedicles on the concavity side, except for the apical vertebra, and alternate pedicles on the convexity side, using 10 to 14 screws. Screw density was calculated as the ratio between the number of screws and pedicles fused. RESULTS Groups were homogeneous regarding preoperative clinical and functional variables, surgery time, and intraoperative bleeding volume. Group 2 had a higher number of screws, average density of pedicle screws, and cost of treatment (p = .000). The number of fused levels was similar between groups. Two years postoperatively, all radiographic variables were homogeneous between groups (mean correction of main thoracic curve was 68.5% in Group 1 and 67.9% in Group 2), but Group 2 achieved better clinical correction of the thoracic hump (p = .000). Both presented significant improvement in the 5 domains of Scoliosis Research Society Score-30. CONCLUSIONS In AIS patients with Lenke 1A/B curves of 45° to 70°, treatment with a higher pedicle screw density construct was significantly more expensive but had statistically similar functional results and radiographic correction. The denser construct achieved better correction of the thoracic hump 2 years after surgery.
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Affiliation(s)
| | - Osmar Avanzi
- Department of Orthopedics and Traumatology, Faculdade de Ciências Médicas, Santa Casa de Misericórdia de São Paulo, Brazil
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Comparative analysis of posterior fusion constructs as treatments for middle and posterior column injuries: an in vitro biomechanical investigation. Clin Biomech (Bristol, Avon) 2013; 28:483-9. [PMID: 23707137 DOI: 10.1016/j.clinbiomech.2013.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 04/30/2013] [Accepted: 05/01/2013] [Indexed: 02/07/2023]
Abstract
BACKGROUND Titanium pedicle screw-rod instrumentation is considered a standard treatment for spinal instability; however, the advantages of cobalt-chromium over titanium is generating interest in orthopedic practice. The aim of this study was to compare titanium versus cobalt-chromium rods in posterior fusion through in vitro biomechanical testing. METHODS Posterior and middle column injuries were simulated at L3-L5 in six cadaveric L1-S1 human spines and different pedicle screw constructs were implanted. Specimens were subjected to flexibility tests and range of motion, intradiscal pressure and axial rotation energy loss were statistically compared among five conditions: intact, titanium rods (with and without transverse connectors) and cobalt-chromium rods (with and without transverse connectors). FINDINGS All fusion constructs significantly (P<0.01) decreased range of motion in flexion-extension and lateral bending with respect to intact, but no significant differences (P>0.05) were observed in axial rotation among all conditions. Intradiscal pressure significantly increased (P≤0.01) after fusion, except for the cobalt-chrome conditions in extension (P≥0.06), and no significant differences (P>0.99) were found among fixation constructs. In terms of energy loss, differences became significant P≤0.05 between the cobalt-chrome with transverse connector condition with respect to the cobalt-chrome and titanium conditions. INTERPRETATION There is not enough evidence to support that the cobalt-chrome rods performed biomechanically different than the titanium rods. The inclusion of the transverse connector only increased stability for the cobalt-chromium construct in axial rotation.
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Abstract
STUDY DESIGN A 10-point questionnaire was constructed to identify the philosophy of surgeons on various aspects of scoliosis surgery, such as choice of implant, bone graft, autologous blood transfusion, cord monitoring, and computer-assisted surgery. Comparisons were then made with recommendations published in the spinal literature. OBJECTIVE To determine certain aspects of the current practice of scoliosis surgery in the United Kingdom. SUMMARY OF BACKGROUND DATA Guidelines for good clinical practice in spinal deformity surgery are available in the United Kingdom but do not cover a number of controversial issues. METHODS Consultants and fellows attended the 2009 British Scoliosis Society meeting. Fifty questionnaires were completed by 45 consultants and 5 fellows. RESULTS All pedicle screw constructs favored by 25 of 50, hybrid 24 of 50 (1 undecided). Posterior construct of fewer than 10 levels, 20 of 50 would not cross-link, 11 of 50 used 1, and 19 of 20 used 2 or more. More than 10 levels 17 of 50 considered cross-links unnecessary, 4 of 50 used 1 and 29 of 50 used 2 or more. Eighty-eight percent preferred titanium alloy implants, whereas others used a mixture of stainless steel and cobalt chrome. When using bone graft, respondents used bone substitutes (24), iliac crest graft (14), allograft (12) and demineralized bone matrix (9) in addition to local bone. Ten of 50 would use recombinant bone morphogenetic protein (3 for revision cases only). Thirty-nine of 50 routinely used intraoperative cell salvage and 4 of 50 never used autologous blood. All used cord monitoring: sensory (19 of 50), motor (2 of 50), and combined (29 of 50). None used computer-aided surgery. Twenty-six operated alone, 12 operated in pairs, and 12 varied depending on type of case. CONCLUSION This survey shows interesting variations in scoliosis surgery in the United Kingdom. It may reflect the conflicting evidence in the literature.
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Lehman RA, Dmitriev AE, Wilson KW. Biomechanical analysis of the C2 intralaminar fixation technique using a cross-link and offset connector for an unstable atlantoaxial joint. Spine J 2012; 12:151-6. [PMID: 22405616 DOI: 10.1016/j.spinee.2012.01.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 01/24/2012] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT C2 intralaminar screws offer the advantage of avoiding the vertebral artery; however, biomechanical studies have demonstrated inferiority of C2 intralaminar screw fixation compared with C2 intrapedicular fixation in the presence of an odontoid fracture. Addition of a transverse cross-link may improve stability afforded by the lamina screws but will require the use of offset connectors to complete the construct. PURPOSE The aims of this project were to evaluate whether transverse cross-links can add adequate stability to atlantoaxial constructs using C1 lateral mass and C2 intralaminar screw fixation. The secondary objective was to determine the biomechanical contribution of the C2 offset connectors. STUDY DESIGN In vitro human cadaveric biomechanical study. METHODS Ten cadaveric specimens were obtained and instrumented with C1 lateral mass, C2 pedicle, and C2 intralaminar screws. After intact spine testing, each C1-C2 construct was nondestructively evaluated under axial rotation (AR), flexion extension (FE), and lateral bending (LB). Intralaminar fixation was tested with and without offset connectors, which allowed for cross-link addition to the construct. After normal state evaluation, the odontoid was resected and analyses were repeated. RESULTS Postreconstruction range of motion in AR, FE, and LB showed no significant differences between the four fixation constructs in the stable specimens. Transpedicular fixation at C2 proved superior to intralaminar techniques without a cross-link in AR and LB after destabilization with an odontoidectomy. The addition of a cross-link to the intralaminar construct improved segmental AR and LB stability to the level afforded by the transpedicular fixation. Offset connectors appeared to marginally weaken the intralaminar fixation, but the findings were not significant. CONCLUSIONS Coupled with an offset connector and a cross-link, C2 intralaminar screws offer similar segmental stability to intrapedicular fixation in the presence of an unstable dens fracture. Lateral offset connectors at C2 do not significantly compromise stability of C1 lateral mass-C2 intralaminar fixation.
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Affiliation(s)
- Ronald A Lehman
- Department of Orthopaedic Surgery and Rehabilitation, Walter Reed National Military Medical Center, 8901 Wisconsin Ave, Bethesda, MD 20889, USA.
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Wang H, Li C, Liu T, Zhao WD, Zhou Y. Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study. Indian J Orthop 2012; 46:395-401. [PMID: 22912513 PMCID: PMC3421928 DOI: 10.4103/0019-5413.98827] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical studies to support the claim. The aim of this study was to evaluate the effect of adding intermediate pedicle screws at the level of a fracture on the stiffness of a short-segment pedicle fixation using monoaxial or polyaxial screws and to compare the strength of monoaxial and polyaxial screws in the calf spine fracture model. MATERIALS AND METHODS Flexibility of 12 fresh-frozen calf lumbar spine specimens was evaluated in all planes. An unstable burst fracture model was created at the level of L3 by the pre-injury and dropped-mass technique. The specimens were randomly divided into monoaxial pedicle screw (MPS) and polyaxial pedicle screw (PPS) groups. Flexibility was retested without and with intermediate screws (MPSi and PPSi) placed at the level of fracture in addition to standard screws placed at L2 and L4. RESULTS The addition of intermediate screws significantly increased the stability of the constructs, as measured by a decreased range of motion (ROM) in flexion, extension, and lateral bending in both MPS and PPS groups (P < 0.05). There was neither any significant difference in the ROM in the spines of the two groups before injury, nor a difference in the ROM between the MPSi and PPSi groups (P > 0.05), but there was a significant difference between MPS and PPS in flexion and extension in the short-segment fixation group (P < 0.05). CONCLUSIONS The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw.
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Affiliation(s)
- Hongwei Wang
- Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, Xinqiao Street, Chongqing, China
| | - Changqing Li
- Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, Xinqiao Street, Chongqing, China
| | - Tao Liu
- Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, Xinqiao Street, Chongqing, China
| | - Wei-dong Zhao
- Department of Anatomy, Biomechanical Laboratory, Southern Medical University, Guangzhou 510515, China
| | - Yue Zhou
- Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, Xinqiao Street, Chongqing, China,Address for correspondence: Dr. Yue Zhou, Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, 83 Xinqiao Street, Chongqing 400037, PR China. E-mail:
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Shaw MN, Morel EP, Utter PA, Gussous YM, Ginoux L, Berglund LJ, Gay RE, Krauss WE. Transverse connectors providing increased stability to the cervical spine rod-screw construct: an in vitro human cadaveric study. J Neurosurg Spine 2011; 14:719-25. [DOI: 10.3171/2011.1.spine10411] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
The object of this study was to determine if the addition of transverse connectors (TCs) to a rod-screw construct leads to increased stabilization of the cervical spine.
Methods
Eleven human cadaveric cervical spines (C2–T1) were used to examine the effect of adding connectors to a C3–7 rod-screw construct in 3 models of instability: 1) C3–6 wide laminectomy, 2) wide laminectomy and 50% foraminotomy at C4–5 and C5–6, and 3) wide laminectomy with full medial to lateral foraminotomy. Following each destabilization procedure, specimens were tested with no TC, 1 TC between the C-5 screws, and 2 TCs between the C-4 and C-6 screws. Testing of the connectors was conducted in random order. Specimens were subjected to ± 2 Nm of torque in flexion and extension, lateral bending, and axial rotation. Range of motion was determined for each experimental condition. Statistical comparisons were made between the destabilized and intact conditions, and between the addition of TCs and the absence of TCs.
Results
The progressive destabilization procedures significantly increased motion. The addition of TCs did not significantly change motion in flexion and extension. Lateral bending was significantly decreased with 2 connectors, but not with 1 connector. The greatest effect was on axial rotation. In general, 2 TCs were more restrictive than 1 TC, and decreased motion 10% more than fixation alone.
Conclusions
Regardless of the degree of cervical destabilization, 1 or 2 TCs decreased motion compared with rods and screws alone. Axial rotation was most affected. Transverse connectors effectively increase the rigidity of rod-screw constructs in the cervical spine. Severe cervical instability can be overcome with the use of 2 TCs, but in cases in which 2 cannot be used, 1 should be adequate and superior to none.
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Affiliation(s)
| | | | | | | | | | | | - Ralph E. Gay
- 1Biomechanics Laboratory, and
- 3Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota
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Abstract
There are three basic concepts that are important to the biomechanics of pedicle screw-based instrumentation. First, the outer diameter of the screw determines pullout strength, while the inner diameter determines fatigue strength. Secondly, when inserting a pedicle screw, the dorsal cortex of the spine should not be violated and the screws on each side should converge and be of good length. Thirdly, fixation can be augmented in cases of severe osteoporosis or revision. A trajectory parallel or caudal to the superior endplate can minimise breakage of the screw from repeated axial loading. Straight insertion of the pedicle screw in the mid-sagittal plane provides the strongest stability. Rotational stability can be improved by adding transverse connectors. The indications for their use include anterior column instability, and the correction of rotational deformity.
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Affiliation(s)
- W Cho
- Department of Orthopaedic Surgery, University of Virginia, 114 Old Fifth Circle, Charlottesville, Virginia 22903, USA.
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