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Abstract
Pseudarthrosis of the cervical spine represents a common and challenging problem for spine surgeons. Rates vary greatly from as low as 0%-20% to >60% and depend heavily on patient factors, approach, and number of levels. While some patients remain asymptomatic from pseudarthrosis, many require revision surgery due to instability, continued neck pain, or radiculopathy/myelopathy. We aimed to provide a practical, narrative review of cervical pseudarthrosis to address the following areas: (1) definitions, (2) incidence, (3) risk factors, (4) presentation and workup, (5) treatment decision-making, and (6) postoperative care. It is our hope the current review provides a concise summary for how to diagnose and treat challenging cervical nonunions.
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Affiliation(s)
- Scott L Zuckerman
- Department of Neurosurgery, Vanderbilt University Medical Center, Nashville, TN
- Department of Orthopedic Surgery, Columbia University Medical Center, New York, NY
| | - Clinton J Devin
- Steamboat Orthopedic and Spine Institute, Steamboat Springs, CO
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Comparison between selective caudal fixed screw construct and all variable screw construct in anterior cervical discectomy and fusion. Sci Rep 2021; 11:10573. [PMID: 34012036 PMCID: PMC8134452 DOI: 10.1038/s41598-021-90121-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 04/19/2021] [Indexed: 11/19/2022] Open
Abstract
This retrospective comparative study aimed to compare the efficacy of selective caudal fixed screw constructs with all variable screw constructs in anterior cervical discectomy and fusion (ACDF). Thirty-five patients who underwent surgery using selective caudal fixed screw construct (SF group) were compared with 44 patients who underwent surgery using all variable constructs (AV group). The fusion rate, subsidence, adjacent level ossification development (ALOD), adjacent segmental disease (ASD), and plate-adjacent disc space distance were assessed. The one-year fusion rates assessed by computed tomography bone bridging and interspinous motion as well as the significant subsidence rate did not differ significantly between the AV and SF groups. The ALOD and ASD rates and plate-adjacent disc space distances did not significantly differ between the two groups at both the cranial and caudal adjacent levels. The number of operated levels was significantly associated with pseudarthrosis in the logistic regression analysis. The stability provided by the locking mechanism of the fixed screw did not lead to an increased fusion rate at the caudal level. Therefore, the screw type should be selected based on individual patient’s anatomy and surgeon’s experience without concern for increased complications caused by screw type.
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Song KJ, Choi BW, Ham DH, Kim HJ. Prognosis of Hardware-Related Problems in Anterior Cervical Discectomy and Fusion with Cage and Plate Constructs. World Neurosurg 2019; 134:e249-e255. [PMID: 31629142 DOI: 10.1016/j.wneu.2019.10.042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 10/05/2019] [Accepted: 10/08/2019] [Indexed: 10/25/2022]
Abstract
OBJECTIVE To analyze hardware-related problems and their prognoses after anterior cervical discectomy and fusion (ACDF) using cages and plates for degenerative and traumatic cervical disc diseases. METHODS The study included 808 patients who underwent anterior cervical discectomy and fusion for degenerative and traumatic disc diseases with >1 year of follow-up. We investigated time of onset and progression of problems associated with instrumentation and cage usage. The mean follow-up time was 3.4 years. Type of plate, range and level of fusion, patient factors (age, sex, body mass index, and bone mineral density), and local kyphosis were evaluated. RESULTS Complications were found in 132 cases (16.5%), including subsidence in 69 cases, plate loosening in 8 cases, screw loosening in 8 cases, screw breakage in 1 case, and multiple complications in 36 cases. In 3 cases, additional posterior cervical surgery was performed. One case needed hardware revision. There were no esophageal, tracheal, or neurovascular structural injuries secondary to metal failure. There were no significant differences in type of plate, level of surgery, or patient factors. The greater the number of fusion segments, the greater the incidence of complications (P = 0.001). The clinical outcomes improved regardless of the complications (P = 0.083). CONCLUSIONS Most hardware-related complications are not symptomatic and can be treated conservatively. Only a few cases need revision surgery. Precise surgical techniques are needed in multilevel anterior cervical discectomy and fusion (>3 levels) because of the increased complication rate.
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Affiliation(s)
- Kyung-Jin Song
- Department of Orthopaedic Surgery, Chonbuk National University Medical School, Jeonju, Korea
| | - Byung-Wan Choi
- Department of Orthopedic Surgery, Inje University, Haeundae Paik Hospital, Busan, Korea.
| | - Dong Hun Ham
- Department of Orthopaedic Surgery, Chonbuk National University Medical School, Jeonju, Korea
| | - Hyeong Jik Kim
- Department of Orthopaedic Surgery, Chonbuk National University Medical School, Jeonju, Korea
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Stiffness Matters: Part II-The Effects of Plate Stiffness on Load-Sharing and the Progression of Fusion Following Anterior Cervical Discectomy and Fusion In Vivo. Spine (Phila Pa 1976) 2018; 43:E1069-E1076. [PMID: 29557926 DOI: 10.1097/brs.0000000000002644] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Real time in vivo measurement of forces in the cervical spine of goats following anterior cervical discectomy and fusion (ACDF). OBJECTIVE To measure interbody forces in the cervical spine during the time course of fusion following ACDF with plates of different stiffnesses. SUMMARY OF BACKGROUND DATA Following ACDF, the biomechanics of the arthrodesis is largely dictated by the plate. The properties of the plate prescribe the extent of load-sharing through the disc space versus the extent of stress-shielding. Load-sharing promotes interbody bone formation and stress-shielding can inhibit maturation of bone. However, these principles have never been validated in vivo. Measuring in vivo biomechanics of the cervical spine is critical to understanding the complex relationships between implant design, interbody loading, load-sharing, and the progression of fusion. METHODS Anterior cervical plates of distinct bending stiffnesses were placed surgically following ACDF in goats. A validated custom force-sensing interbody implant was placed in the disc space to measure load-sharing in the spine. Interbody loads were measured in vivo in real time during the course of fusion for each plate. RESULTS Interbody forces during flexion/extension were highly dynamic. In animals that received high stiffness plates, maximum forces were in extension whereas in animals that received lower stiffness plates, maximum forces were in flexion. As fusion progressed, interbody load magnitude decreased. CONCLUSION The magnitude of interbody forces in the cervical spine is dynamic and correlates to activity and posture of the head and neck. The magnitude and consistency of forces in the interbody space correlates to plate stiffness with more compliant plates resulting in more consistent load-sharing. The magnitude of interbody forces decreases as fusion matures suggesting that smart interbody implants may be used as a diagnostic tool to indicate the progression of interbody fusion. LEVEL OF EVIDENCE N/A.
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Stiffness Matters: Part I-The Effects of Plate Stiffness on the Biomechanics of ACDF In Vitro. Spine (Phila Pa 1976) 2018; 43:E1061-E1068. [PMID: 29547464 DOI: 10.1097/brs.0000000000002643] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN In vitro biomechanical testing of human cadaveric cervical and goat cervical motion segments. OBJECTIVE The aim of this study was to measure the effects of plate stiffness on load-sharing, instantaneous axis of rotation (IAR), and posterior element loading after anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA ACDF is intended to create an environment, which facilitates sufficient stability and biomechanical conditions to promote bone formation. The relationship between cervical plate stiffness, load-sharing, and the IAR is complex. The ideal cervical plate is sufficiently stiff to limit interbody motion but is compliant enough to facilitate load-sharing rather than stress-shielding. METHODS Anterior cervical plates of distinct bending stiffnesses were applied to human and goat cervical motion segments following ACDF. A validated custom force-sensing interbody implant was placed in the disc space to measure load-sharing in the spine. Interbody loads, posterior element strain, and the IAR were measured during flexion/extension for each plate. RESULTS Load-sharing in the interbody space, posterior element strain, and the location of the IAR were all significantly affected by plate stiffness. More compliant plates resulted in more load sharing, less posterior element strain, and a more dorsally located IAR relative to stiffer plates. CONCLUSION A more compliant plate fosters more consistent load-sharing through the entire range of flexion/extension, which may promote faster bone formation and better fusion. A more compliant plate causes less posterior element strain, which may reduce facet joint loads and in turn reduce facet joint arthrosis. An ideal plate may be one that is stiff enough to minimize interbody motion and yet compliant enough to allow consistent load-sharing and minimal increase in posterior element strain. LEVEL OF EVIDENCE N/A.
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Kani KK, Chew FS. Anterior cervical discectomy and fusion: review and update for radiologists. Skeletal Radiol 2018; 47:7-17. [PMID: 29058045 DOI: 10.1007/s00256-017-2798-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 10/06/2017] [Accepted: 10/11/2017] [Indexed: 02/02/2023]
Abstract
OBJECTIVES The goals of this article are to describe the various types of interbody grafts and anterior cervical plating systems, techniques for optimizing evaluation of cervical spine metallic implants on CT and MR imaging, expected appearance and complications of ACDF on postoperative imaging and imaging assessment of fusion. Optimization for optimizing metal induced artifacts. CONCLUSION Currently, ACDF is the most commonly performed surgical procedure for degenerative cervical spine disease. Interbody fusion is performed with bone grafts or interbody spacers, and may be supplemented with anterior cervical plating. Compressive pathologies at the vertebral body level may be addressed by simultaneous corpectomy. Postoperatively, imaging plays an integral role in routine screening of asymptomatic individuals, fusion assessment and evaluation of complications.
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Affiliation(s)
- Kimia Khalatbari Kani
- Department of Radiology, University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Felix S Chew
- Department of Radiology, University of Washington, 4245 Roosevelt Way NE, Box 354755, Seattle, WA, 98105, USA
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Yeh KT, Lee RP, Chen IH, Yu TC, Liu KL, Peng CH, Wang JH, Chang PY, Wu WT. Fresh frozen cortical strut allograft in two-level anterior cervical corpectomy and fusion. PLoS One 2017; 12:e0183112. [PMID: 28841652 PMCID: PMC5571964 DOI: 10.1371/journal.pone.0183112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 07/28/2017] [Indexed: 11/18/2022] Open
Abstract
Anterior cervical corpectomy and fusion (ACCF) is one of the main surgical strategies for the management of multilevel cervical spondylotic myelopathy (MCSM). High complication rates of graft bone fracture, resorption, displacement, and fusion collapse or pseudarthrosis have been previously reported. The strategies to prevent the aforementioned complications include using fresh frozen cortical strut allograft (FFCSA) to keep most of the original bone quality and using additional anterior plate fixation to improve the fusion stability and union rate. In this study, we evaluated 4-year follow-ups for surgical outcomes and analyzed the risk factors of MCSM patients who received 2-level ACCF with FFCSA and titanium dynamic plate fixation. We retrospectively collected preoperative and postoperative radiographic and clinical data of patients from 2005 to 2009; the inclusion criteria were having been diagnosed as MCSM and having received 2-level ACCF with an FFCSA fibular shaft and an anterior dynamic plate. The cervical curvature lordosis improved and the neurogenic function recovered well postoperatively. Visual analog scale for neck pain and neck disability index scores both decreased after 12 and 48 months following surgery. The Japanese Orthopaedic Association score recovery rate at postoperative 4 years was 87.5%. Fusion rates achieved 100% at 12 months. The preoperative Nurick score seemed to be the only significant risk factor correlated with the functional recovery rate at 4 years after the surgery. In conclusion, based on a minimum 4-year follow-up of 2-level ACCF with FFCSA and dynamic titanium plates for patients with MCSM, the surgical results were satisfying and the complication rates were low.
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Affiliation(s)
- Kuang-Ting Yeh
- Department of Orthopedics, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
- School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Ru-Ping Lee
- Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan
| | - Ing-Ho Chen
- Department of Orthopedics, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
- School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Tzai-Chiu Yu
- Department of Orthopedics, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
- School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Kuan-Lin Liu
- Department of Orthopedics, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Cheng-Huan Peng
- Department of Orthopedics, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Jen-Hung Wang
- Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Pau-Yuan Chang
- Department of Radiology, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Wen-Tien Wu
- Department of Orthopedics, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
- School of Medicine, Tzu Chi University, Hualien, Taiwan
- Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan
- * E-mail:
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The Effect of Dynamic Versus Static Plating Systems on Fusion Rates and Complications in 1-Level and/or 2-Level Anterior Cervical Discectomy and Fusion: A Systematic Review. Clin Spine Surg 2017; 30:20-26. [PMID: 27898451 DOI: 10.1097/bsd.0000000000000453] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
STUDY DESIGN A systematic review. OBJECTIVE To determine the effect of plate design on fusion rates in patients undergoing a 1- and 2-level anterior cervical discectomy and fusion (ACDF). METHODS Articles published between January 1, 2002 and January 1, 2015 were systematically reviewed to determine the fusion rate of 1- and 2-level ACDFs using either a fully constrained or semiconstrained locking plate. Additional variables that were collected included the number of levels, the type of graft/cage used, the study design, the method for determining fusion, and complications. RESULTS Fifty-two articles and 3053 patients were included. No significant difference in the fusion rate for 1- and 2-level ACDF using a fully constrained plate (96.1%) and a semiconstrained plate (95.29%) was identified (P=0.84). No difference (P=0.85) in the total complication rate between fully constrained plates (3.20%) and semiconstrained plates (3.66%), or the rate of complications that required a revision (2.17% vs. 2.41%, P=0.82) was identified. However, semiconstrained plates had a nonsignificant increase in total dysphagia rates (odds ratio=1.660, P=0.28) and short-term dysphagia rates (odds ratio=2.349, P=0.10). CONCLUSIONS In patients undergoing a 1- or 2-level ACDF, there is no significant difference in the fusion or complication rate between fully constrained plates and semiconstrained plates. LEVEL OF EVIDENCE Level II-systematic review.
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Yan Y, Bell KM, Hartman RA, Hu J, Wang W, Kang JD, Lee JY. In vitro evaluation of translating and rotating plates using a robot testing system under follower load. 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 2015; 26:189-199. [PMID: 26321003 DOI: 10.1007/s00586-015-4203-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 08/20/2015] [Accepted: 08/20/2015] [Indexed: 11/25/2022]
Abstract
BACKGROUND CONTEXT Various modifications to standard "rigid" anterior cervical plate designs (constrained plate) have been developed that allow for some degree of axial translation and/or rotation of the plate (semi-constrained plate)-theoretically promoting proper load sharing with the graft and improved fusion rates. However, previous studies about rigid and dynamic plates have not examined the influence of simulated muscle loading. PURPOSE The objective of this study was to compare rigid, translating, and rotating plates for single-level corpectomy procedures using a robot testing system with follower load. STUDY DESIGN In-vitro biomechanical test. METHODS N = 15 fresh-frozen human (C3-7) cervical specimens were biomechanically tested. The follower load was applied to the specimens at the neutral position from 0 to 100 N. Specimens were randomized into a rigid plate group, a translating plate group and a rotating plate group and then tested in flexion, extension, lateral bending and axial rotation to a pure moment target of 2.0 Nm under 100N of follower load. Range of motion, load sharing, and adjacent level effects were analyzed using a repeated measures analysis of variance (ANOVA). RESULTS No significant differences were observed between the translating plate and the rigid plate on load sharing at neutral position and C4-6 ROM, but the translating plate was able to maintain load through the graft at a desired level during flexion. The rotating plate shared less load than rigid and translating plates in the neutral position, but cannot maintain the graft load during flexion. CONCLUSIONS This study demonstrated that, in the presence of simulated muscle loading (follower load), the translating plate demonstrated superior performance for load sharing compared to the rigid and rotating plates.
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Affiliation(s)
- Y Yan
- Department of Spine Surgery, The First Affiliated Hospital of University of South China, Hengyang, People's Republic of China
- C/O Ferguson Laboratory for Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 200 Lothrop Street, E1612 BST, Pittsburgh, PA, 15213, USA
- Department of Spine Surgery, Xiangya Hospital, Central South University, Changsha, People's Republic of China
| | - K M Bell
- C/O Ferguson Laboratory for Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 200 Lothrop Street, E1612 BST, Pittsburgh, PA, 15213, USA.
| | - R A Hartman
- C/O Ferguson Laboratory for Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 200 Lothrop Street, E1612 BST, Pittsburgh, PA, 15213, USA
| | - J Hu
- Department of Spine Surgery, Xiangya Hospital, Central South University, Changsha, People's Republic of China
| | - W Wang
- Department of Spine Surgery, The First Affiliated Hospital of University of South China, Hengyang, People's Republic of China
| | - J D Kang
- C/O Ferguson Laboratory for Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 200 Lothrop Street, E1612 BST, Pittsburgh, PA, 15213, USA
| | - J Y Lee
- C/O Ferguson Laboratory for Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 200 Lothrop Street, E1612 BST, Pittsburgh, PA, 15213, USA
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Connor DE, Shamieh KS, Ogden AL, Mukherjee DP, Sin A, Nanda A. Biomechanical performance of rigid compared to dynamic anterior cervical plating: analysis of adjacent upper and lower level compressive forces. J Clin Neurosci 2012; 19:1706-10. [DOI: 10.1016/j.jocn.2012.03.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 03/05/2012] [Accepted: 03/17/2012] [Indexed: 11/30/2022]
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Li H, Dai LY. A systematic review of complications in cervical spine surgery for ossification of the posterior longitudinal ligament. Spine J 2011; 11:1049-57. [PMID: 22015235 DOI: 10.1016/j.spinee.2011.09.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 07/25/2011] [Accepted: 09/07/2011] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Surgical management of ossification of the posterior longitudinal ligament (OPLL) is associated with complications. However, surgical complications for OPLL have not been clearly documented. PURPOSE To review and summarize the incidence of surgical complications of OPLL in the cervical spine and evaluate the impact of surgical approach (anterior or posterior), year of study publication, follow-up duration, and the surgical outcome on complication incidence. STUDY DESIGN Systematic review. METHODS An English literature review was conducted especially on surgical complications of cervical OPLL. The incidence of complications was statistically summarized, with its correlation to surgical approaches, year of study publications, follow-up duration, and the surgical outcome was statistically evaluated. RESULTS Twenty-seven retrospective studies, including a total of 1,558 patients, were reviewed. The overall incidence of surgical complications of cervical OPLL was 21.8%. Neurologic deficit (8.3%, overall rate), cerebrospinal fluid leakage (CFL) (5.1%), axial pain (3.5%), and implant complications (3.5%) were relatively common. The incidence of complications for posterior approach was not statistically different from those for anterior procedures. However, with regard to individual complication, C5 palsy and axial pain occurred more frequently in patients approached posteriorly, whereas CFL, implant complications, hoarseness, dysphagia, and dyspnea appeared more common in anterior cases. CONCLUSIONS There is a relatively high incidence of surgical complications for cervical OPLL compared with other cervical degeneration diseases. It is, therefore, necessary for surgeons to take into consideration the risk of surgical complications when communicating with patients for decision making and to alert complications during or after surgical procedures.
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Affiliation(s)
- Hai Li
- Department of Orthopedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Rd, Shanghai 200092, China
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Truumees E. Commentary: Incorporating new technology into spine care: the case of resorbable cervical plates. Spine J 2011; 11:1009-14. [PMID: 22122833 DOI: 10.1016/j.spinee.2011.10.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 10/21/2011] [Indexed: 02/03/2023]
Abstract
Commentary on: Lebl DR, Bono CM, Metkar US, et al. Bioabsorbable anterior cervical plate fixation for single-level degenerative disorders: early clinical and radiographic experience. Spine J 2011;11:1002-8 (in this issue).
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Affiliation(s)
- Eeric Truumees
- Seton Spine & Scoliosis Center, Seton Brain and Spine Institute, University Medical Center at Brackenridge, 1600 West 38th St, Suite 200, Austin, TX 78731, USA.
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Reid JJ, Johnson JS, Wang JC. Challenges to bone formation in spinal fusion. J Biomech 2010; 44:213-20. [PMID: 21071030 DOI: 10.1016/j.jbiomech.2010.10.021] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 10/13/2010] [Indexed: 01/10/2023]
Abstract
Spinal arthrodesis continues to expand in clinical indications and surgical practice. Despite a century of study, failure of bone formation or pseudarthrosis can occur in individual patients with debilitating clinical symptoms. Here we review biological and technical aspects of spinal fusion under active investigation, describe relevant biomechanics in health and disease, and identify the possibilities and limitations of translational animal models. The purpose of this article is to foster collaborative efforts with researchers who model bone hierarchy. The induction of heterotopic osteosynthesis requires a complex balance of biologic factors and operative technique to achieve successful fusion. Anatomical considerations of each spinal region including blood supply, osteology, and biomechanics predispose a fusion site to robust or insufficient bone formation. Careful preparation of the fusion site and appropriate selection of graft materials remains critical but is sometimes guided by conflicting evidence from the long-bone literature. Modern techniques of graft site preparation and instrumentation have evolved for every segment of the vertebral column. Despite validated biomechanical studies of modern instrumentation, a correlation with superior clinical outcomes is difficult to demonstrate. In many cases, adjuvant biologic therapies with allograft and synthetic cages have been used successfully to reproduce the enhancement of fusion rates observed with cancellous and tricortical autograft. Current areas of investigation comprise materials science, stem cell therapies, recombinant growth factors, scaffolds and biologic delivery systems, and minimally invasive surgical techniques to optimize the biologic response to intervention. Diverse animal models are required to approach the breadth of spinal pathology and novel therapeutics.
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Affiliation(s)
- Jeremy J Reid
- Department of Orthopaedic Surgery, David Geffen School of Medicine, University of California, Los Angeles, USA
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Fogel GR, Li Z, Liu W, Liao Z, Wu J, Zhou W. In vitro evaluation of stiffness and load sharing in a two-level corpectomy: comparison of static and dynamic cervical plates. Spine J 2010; 10:417-21. [PMID: 20338828 DOI: 10.1016/j.spinee.2010.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 12/29/2009] [Accepted: 02/05/2010] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Anterior cervical plating has been accepted in corpectomy and fusion of the cervical spine. Constrained plates were criticized for stress shielding that may lead to subsidence and pseudarthrosis. A dynamic plate allows load sharing as the graft subsides. Ideally, the dynamic plate design should maintain adequate stiffness of the construct while providing a reasonable load sharing with the strut graft. PURPOSE The purpose of the study was to compare dynamic and static plate kinematics with graft subsidence. STUDY DESIGN/SETTING The study designed was an in vitro biomechanical study in a porcine cervical spine model. METHODS Twelve spines were initially tested in intact condition with 20-N axial load in 15 degrees of flexion and extension range of motion (ROM). Then, a two-level corpectomy was created in all specimens with spines randomized to receive either a static or dynamic plate. The spines were retested under identical conditions with optimal length and undersized graft. Range of motion and graft loading were analyzed with a one-way analysis of variance (p<.05). RESULTS Both plates significantly limited ROM compared with the intact spine in both graft length conditions. In extension graft, load was significantly higher (p=.001) in the static plate with optimal length, and in flexion, there was a significant loss of graft load (p=.0004). In flexion, the dynamic plate with undersized graft demonstrated significantly more load sustained (p=.0004). CONCLUSIONS Both plates reasonably limited the ROM of the corpectomy. The static plate had significantly higher graft loads in extension and significant loss of graft load in flexion, whereas the dynamic plate maintained a reasonable graft load in ROM even when graft contact was imperfect.
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Affiliation(s)
- Guy R Fogel
- Spine Orthopedic Institute, 21 Spurs Lane, San Antonio, TX 78240, USA
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Kelly MP, Mok JM, Berven S. Dynamic constructs for spinal fusion: an evidence-based review. Orthop Clin North Am 2010; 41:203-15. [PMID: 20399359 DOI: 10.1016/j.ocl.2009.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Dynamic stabilization of the spine has applications in cervical and lumbar degenerative disease and in thoracolumbar trauma. There is little evidence to support the use of dynamic cervical plates rather than rigid anterior cervical fixation. Evidence to support the use of dynamic constructs for fusion in the lumbar spine is also limited. Fusion rates, implant loosening, and failure are significant concerns that limit the adoption of current devices. This article provides a synopsis of the literature on human subjects. There is a need for high-quality evidence for interventions for spinal pathology. An evidence-based approach to the management of spinal disorders will require ongoing assessment of clinical outcomes and comparison of effectiveness between alternatives.
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Affiliation(s)
- Michael P Kelly
- Department of Orthopaedic Surgery, University of California, 500 Parnassus Avenue, MU 320-W, San Francisco, CA 94110, USA.
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