Distraction extension injuries of the cervical spine

Twenty-four consecutive patients with cervical distraction extension injuries were retrospectively reviewed to study the safety and efficacy of various treatment protocols in this type of cervical spine injury. Sixteen of 24 patients with cervical distraction extension injuries underwent surgical stabilization. All patients undergoing surgical stabilization were noted to have a stable fusion at their latest follow-up. There were three instances of surgically related neurologic deterioration as a result of over-distraction of the anterior column interspace at the time of graft placement. The overall mortality rate was 42% in this aged patient population. Anterior reconstruction of the cervical spine with an anterior cervical graft and plate acting as a tension band is the ideal treatment method for stabilization of acute distraction extension injuries involving primarily the soft tissue structures (anterior longitudinal ligament and intervertebral disc). Type 2 injuries, depending on the degree of displacement and the adequacy of closed reduction, may need to be approached initially posteriorly to obtain adequate alignment, followed by an anterior reconstructive procedure. Great care should be taken during anterior graft placement to avoid over-distraction of the spine. If nonsurgical intervention is selected, close regular radiographic follow-up is necessary to detect early vertebral malalignment, which may predispose to spinal cord dysfunction. Older patients sustaining this injury have a high mortality rate.     

The in vitro effects of instrumentation on multilevel cervical strut-graft mechanics

STUDY DESIGN: Biomechanical study using a programmable testing apparatus that replicated physiologic flexion-extension cervical spine motion, and loading mechanics. OBJECTIVES: To determine the influence of anterior, posterior, or combined plating on multilevel cervical strut-graft mechanics in vitro. SUMMARY OF BACKGROUND DATA: The addition of instrumentation does not prevent construct failure in multilevel (more than two levels) cervical corpectomy. METHODS: Six fresh human cadaveric cervical spines (C2-T1) were tested in six sequential conditions that included harvested (H), C4-6 corpectomy, strut grafted, strut grafted with an anterior cervical plate (SGAP), strut grafted with posterior plates (SGPP), and strut grafted with combined anterior and posterior plates (SGAPP). A customized force-sensing strut graft (FSSG) was used to measure axial compression-tension, flexion-extension and lateral bending moments, and axial torsion. Parameters of stiffness, segmental vertebral motion, and strut-graft loads were compared, to determine differences among the spine conditions. RESULTS: Flexion of the strut-grafted spine loaded the FSSG, and extension motion unloaded the FSSG. With the anterior plate, flexion of the SGAP spine significantly unloaded the FSSG; extension loaded the FSSG more than flexion of the unplated spine (P = 0.03). The opposite occurred with the posterior plates (SGPP), where flexion of the spine significantly loaded the FSSG (more than the strut grafted spine) and extension unloaded the FSSG (P < 0.03). The combined construct (SGAPP) counteracted the tension band effect of the individual plates and demonstrated significantly less overall FSSG load change than either plate alone (P = 0.03). CONCLUSIONS: Multilevel cervical instrumentation effectively increases stiffness after corpectomy. However, anterior or posterior plating alone excessively loads the graft with small degrees of motion, which may promote pistoning and failure of multilevel constructs.     

Complications of buttress plate stabilization of cervical corpectomy

STUDY DESIGN: A retrospective analysis of 14 patients treated with cervical corpectomy and buttress plate fixation. OBJECTIVES: To determine the complications of buttress plate fixation following multilevel cervical corpectomies. SUMMARY OF BACKGROUND DATA: Buttress plate fixation of multilevel cervical corpectomy has recently been reported. Biomechanical data suggests that it is preferable to long plates spanning the entire corpectomy site. There are no clinical studies that have specifically addressed the complications of this type of plate fixation. METHODS: The records and radiographs of all patients who had undergone cervical buttress plate fixation following anterior cervical corpectomy for myelopathy were independently reviewed. Twelve of the patients had three-level corpectomies and two had two-level corpectomies. All patients had placement of a short plate at the inferior end of the construct with sufficient overhang to act as a buttress against graft extrusion. Three patients underwent posterior cervical fusion in addition to the anterior procedure. RESULTS: Graft extrusion. One patient had complete graft extrusion on the third post-operative night. A second patient who had undergone circumferential fusion had minimal plate dislodgement secondary to graft settling. Pseudarthrosis. Three patients had pseudarthroses. Two of these required revision posterior surgery. Neurologic. None of the patients suffered neurologic complications. With the exception of the one patient who died, the rest of the patients all improved by at least one Nurick grade. CONCLUSION: The most catastrophic complication in the present series was plate dislodgement causing airway compromise and eventually resulting in death. Surgeons who utilize these types of buttress plates without additional posterior instrumentation should be aware of the potential complications of buttress plate fixation.     

Biomechanical evaluation of a newly developed monocortical expansion screw for use in anterior internal fixation of the cervical spine. In vitro comparison with two established internal fixation systems

STUDY DESIGN: The primary biomechanical stability of anterior internal fixation of the cervical spine obtained with a new monocortical expansion screw in vitro was evaluated. OBJECTIVES: To determine whether the anterior internal fixation of the spine obtained with the new monocortical expansion screw provides biomechanical stability comparable with that obtained with bicortical fixation. SUMMARY OF BACKGROUND DATA: The anterior plate instrumentation used with bicortical screw fixation in the cervical spine provides a primary stability superior to that associated with monocortical screw fixation. However, bicortical screws have the potential to perforate the posterior cortex. Therefore, monocortical instrumentation systems were developed, but without the biomechanical stability associated with bicortical systems. A new expansion screw for monocortical fixation was developed to improve biomechanical stability of monocortical systems. METHODS: Three different internal fixation systems were compared in this study: 1) H-plate with AO 3.5-mm bicortical screws, 2) cervical spine locking plate with monocortical screws, and 3) H-plate with the new monocortical expansion screws. Eight fresh human cadaver spine segments from C4 to C7 were tested in flexion-extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. Five conditions were investigated consecutively: 1) intact spine; 2) uninstrumented spine with the segment C5-C6 destabilized; 3-5) instrumentation of the segment C5-C6 with the three implants mentioned above after removal of the disc and insertion of an interbody spacer. RESULTS: Between bicortical and monocortical expansion screw H-plate fixation, no significant differences were observed in all load cases concerning range of motion and neutral zone. The neutral zone and range of motion were significantly larger for the cervical spine locking plate than for bicortical and monocortical expansion screw fixation in all load cases, except neutral zone for axial rotation versus bicortical screw fixation. The instrumented cases only had a significantly lower range of motion and neutral zone than the intact cases in extension-flexion, whereas for lateral bending and axial rotation no significant differences could be observed. Because the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. CONCLUSIONS: In anterior instrumentation of the cervical spine using a H-plate, the new monocortical expansion screw provides the same biomechanical stability as the bicortical 3.5-mm AO screw and a significantly better biomechanical stability than the cervical spine locking plate. Therefore, the expansion screw may be an alternative to the bicortical fixation and does not involve the risk of penetration of the posterior vertebral body cortex.     

Technic of ventral spondylodesis of the lower cervical spine

Anterior fusion of the lower cervical spine is usually performed without difficulty. The surgical technique is simple and normally involves little risk. The indication and technique depend completely on the clinical picture; otherwise, the results are unavoidably poor. A slipped cervical disc is operated on using the Smith-Robinson or Cloward procedure. If extensive decompression with resection of dorsal osteophytes is required, the Cloward technique is preferable due to the superior view of the spinal canal. In dislocations or dislocation fractures of the cervical spine requiring decompression and fusion from the anterior approach, the spine should be stabilized with a bone graft and plate. An anterior approach increases the instability due to damage to the posterior ligaments in flexion injuries. Fusion is usually performed with autologous iliac or fibular grafts, which show good ingrowth but different load-bearing properties. Multisegmental fusions or defects following tumor resections can be bridged with deep-frozen homologous grafts. To achieve immediate stability PMMA implants may be necessary. Implants of bioactive glass ceramics may prove useful in the future.     

下颈椎小关节突脱位前路稳定手术疗效分析

目的探讨下颈椎小关节脱位前路融合内固定的临床效果。方法39例新鲜下颈椎小关节脱位患者,首先在透视下行颅骨牵引复位,34例复位成功(87％)。其中32例完成了颈前路减压、植骨内固定,5例未成功者和3例陈旧性脱位,先行后路切开复位,再一期行前路减压、植骨内固定。结果全部患者均获骨性融合,无迟发性不稳和后凸畸形,术前神经功能正常者术后无一例出现神经损害症状,不全瘫患者术后均有不同程度恢复。结论前路减压融合是治疗下颈椎小关节脱位安全、有效的方法,可获良好的生物学稳定。     

A biomechanical evaluation of cervical spinal stabilization methods in a bovine model. Static and cyclical loading

A bovine model was developed for biomechanical evaluation of surgical procedures stabilizing traumatic cervical injuries disrupting the anterior and posterior spinal column. Cervical spinal segments and C4-5 functional spinal units were tested statically, and C4-5 functional spinal units were tested cyclically in evaluation of 1) the intact cervical spine, 2) Rogers' wiring method, 3) Bohlman's triple-wire technique, 4) sublaminar wiring, 5) anterior cervical plate instrumentation, and 6) posterior hook plate stabilization. Anterior cervical plate instrumentation proved inadequate, and was the least rigid, with axial and flexural loading (P less than 0.05). There was no significant difference between each of the three posterior wiring methods, and all generally restored stability to equal that of the uninjured intact cervical spine. Posterior hook plating with an interspinous bone graft serving as an extension block was the most effective method in reducing flexural stress across the injured C4-5 segment (P less than 0.05). Cyclical in vitro testing was the most sensitive method in highlighting mechanical differences between instrumentation systems, particularly with "on-line" continuous measurement of anterior and posterior strains. Anterior cervical plate stabilization does not appear to confer enough stability in cervical facet injuries to obviate the need for posterior cervical stabilization procedures. The recently developed posterior hook plate technique offers biomechanical advantages that should be weighed against the greater technical precision needed for insertion and the increased potential for neurologic and vascular complications.     

Cervical anterior transpedicular screw fixation. Part I: Study on morphological feasibility,indications, and technical prerequisites

Multilevel cervical spine procedures can challenge the stability of current anterior cervical screw-and-plate systems, particularly in cases of severe three-column subaxial cervical spine injuries and multilevel plated reconstructions in osteoporotic bone. Supplemental posterior instrumentation is therefore recommended to increase primary construct rigidity and diminish early failure rates. The increasing number of successfully performed posterior cervical pedicle screw fixations have enabled more stable fixations, however most cervical pathologies are located anteriorly and preferably addressed by an anterior approach. To combine the advantages of the anterior approach with the superior biomechanical characteristics of cervical pedicle screw fixation, the authors developed a new concept of a cervical anterior transpedicular screw-and-plate system. An in vivo anatomical study was performed to explore the feasibility of anterior transpedicular screw fixation (ATPS) in the cervical spine. The morphological study was conducted based on 29 cervical spine CT scans from healthy patients and measurements were performed on the pedicle sizes, angulations, vertebral body depth, height and width at C2 to T1. Significant morphologic parameters for the new technique are discussed. These parameters include the sagittal and transverse intersection points of the pedicle axis with the anterior vertebral body wall, as well as the distances between sagittal intersection points from C2 to T1. On the basis of these results, standard spine models were reconstructed and used for the conceptual development of a preclinical release prototype of an anterior transpedicular screw-and-plate system. The morphological feasibility of the new technique is demonstrated, and its indications, biomechanical considerations, as well as surgical prerequisites are thoroughly discussed. In the future, the technique of cervical anterior transpedicular screw fixation might diminish the number of failures in the reconstruction of multilevel and three-column cervical spine instabilities, and avoid the need for supplemental posterior instrumentation.     

Anterior cervical spine fusion for unstable fractures

We present in this report the operative method we have used in 7 cases of fracture-dislocation of the lower cervical spine. The technique includes partial resection of the fractured vertebral body, removal of the adjacent discs, excision of posteriorly displaced bone and disc and anterior interbody fusion between the three vertebrae. The latter is performed using a cortico-cancellous graft taken from the iliac crest and further stability is achieved by a small AO plate. All the cases started motion 48 hours after operation without further external support. Although 6 of the cases showed neurological improvement, this cannot be at this stage attributed to the surgical treatment. Nevertheless, none was made worse by the operation.     

Biomechanical testing of an artificial cervical joint and an anterior cervical plate

An in vitro biomechanical study was conducted to determine the effects of fusion and nonfusion anterior cervical instrumentation on cervical spine biomechanics in a multilevel human cadaveric model. Three spine conditions were studied: harvested, single-level artificial cervical joint, and single-level graft with anterior cervical plate. A programmable testing apparatus was used that replicated physiologic flexion/extension and lateral bending. Measurements included vertebral motion, applied load, and bending moments. Relative rotations at the superior, implanted, and inferior motion segment units (MSUs) were normalized with respect to the overall rotation of those three MSUs and compared using a one-way analysis of variance (P < 0.05). Application of an anterior cervical plate decreased motion across the fusion site relative to the harvested and artificial joint spine conditions. The reduced motion was compensated for by an increase in motion at the adjacent segments. Use of an artificial cervical joint did not alter the motion patterns at either the instrumented level or the adjacent segments compared with the harvested condition for all modes of testing.     

椎间盘及部分椎体切除加钛网植骨钛板内固定术治疗单节段颈椎椎间盘突出伴椎体后缘骨赘

目的 评价颈椎椎间盘及相邻椎体部分切除加钛网植骨钛板内固定术治疗单节段颈椎椎间盘退变突出伴相邻椎体后缘骨赘的疗效. 方法 应用颈椎椎间盘及相邻椎体部分切除加钛网植骨钛板内固定术治疗单节段颈椎椎间盘退变突出伴相邻椎体后缘骨赘22例.取颈椎前路手术切口,术中仅切除突出的椎间盘及相邻椎体的1/3～ 1/2,使脊髓得到彻底的减压.再用填满碎骨的钛网植于骨缺损处加用钛板螺丝钉内固定,固定范围仅限于相邻椎体.术前和术后通过神经功能JOA评分、颈部轴性症状、颈椎动态侧位片和颈椎MRI比较临床疗效. 结果 均获随访,平均15(6 ～24)个月,术后JOA评分优良率86.4％,颈部轴性症状减轻,脊髓功能明显得到恢复.颈椎活动度良好.X线检查见钛网植骨及钛板内固定良好,未见不稳现象.MRI示颈髓压迫解除. 结论 颈椎椎间盘及相邻椎体部分切除加钛网植骨钛板内固定术治疗单节段颈椎椎间盘突出伴相邻椎体骨赘效果显著,可最大限度地保留颈椎节段的活动度.     

上位颈椎前路手术咽后入路“窗口”显露技术的临床应用观察

目的：探讨上颈椎前路减压经咽后入路＂窗口＂显露技术在上颈椎损伤手术中的应用。方法：2000年1月至2008年7月手术治疗上位颈椎损伤患者5例,男4例,女1例;年龄16～68岁,平均35岁。C2椎弓骨折（HangmanⅡ型）2例,C2,3椎间盘突出症2例,C2椎体结核1例。所有患者经高位前方咽后入路舌下神经、喉上神经、咽和颈动脉之间的＂窗口＂成功获得显露。Hangman骨折复位后行C2,3椎间盘切除椎间植骨融合内固定。C2,3椎间盘突出症患者行相应椎间盘切除,减压植骨融合内固定。C2椎体结核行病灶清除并植骨等。结果：5例患者均成功在舌下神经、喉上神经、咽和颈动脉之间的＂窗口＂显露出C1前弓-C3椎体。随访5～26个月,平均13.5个月。无伤口感染,无颈部重要血管神经损伤。患者的神经症状恢复良好,所有患者植骨都获得了融合。结论：前方咽后入路的＂窗口＂显露技巧可使上颈椎获得理想的显露,创伤小,切口并发症少,有相关经验后也比较安全。     

陈旧性下颈椎骨折脱位的手术治疗（附42例报告）

目的探讨陈旧性下颈椎骨折脱位的发生原因、手术方法及临床疗效。方法2005年6月～2008年12月,借助椎体间撑开器经颈前路整复脱位椎体、椎体间植骨融合钢板内固定术以及颈后路整复脱位椎体联合应用前路椎体间植骨融合钢板内固定术治疗陈旧性下颈椎骨折伴脱位42例患者。其中,18例患者单纯经颈前路完成脱位颈椎椎体复位,24例前路整复失败病例联合颈后路整复脱位椎体并前路椎体间植骨融合钢板内固定术。观察术后颈椎的稳定性、植骨融合率及神经功能恢复情况。结果全部病例均获得解剖复位,颈椎生理弧度及椎间隙高度恢复正常,术中无神经损害加重及血管损伤等并发症发生,术后颈椎获得即刻稳定性。经6～48个月随访,椎间植骨均获得骨性愈合,螺钉无松动、退出或断裂,颈椎脱位矫正度无丢失,神经功能均有不同程度恢复。结论陈旧性下颈椎骨折脱位应先行前路整复,如失败再行后路手术整复脱位椎体并前路椎体间植骨融合内固定术,对于颈椎陈旧性骨折脱位仍强调恢复颈椎解剖对位的重要性。     

Circumferential cervical surgery for spondylostenosis with kyphosis in two patients with athetoid cerebral palsy.

BACKGROUND: Patients with athetoid cerebral palsy may develop severe degenerative changes in the cervical spine decades earlier than their normal counterparts due to abnormal cervical motion. METHODS: Two patients, 48 and 52 years of age, presented with moderate to severe myelopathy (Nurick Grades IV and V). MR and 3-dimensional CT studies demonstrated severe spondylostenosis with kyphosis in both patients. This necessitated multilevel anterior corpectomy with fusion (C2-C7, C3-C7) using fibula and iliac crest autograft and Orion plating, followed by posterior wiring, fusion using Songer cables, and halo placement. RESULTS: Postoperatively, both patients improved, demonstrating only mild or mild to moderate (Nurick Grades II and III) residual myelopathy. Although both fused posteriorly within 3.5 months, the patient with the fibula graft developed a fracture of the anterior C7 body with mild anterior graft migration, and inferior plate extrusion into the C7-T1 interspace. However, because he has remained asymptomatic for 9 months postoperatively, without dysphagia, removal of the plate has not yet been necessary. CONCLUSIONS: Patients with athetoid cerebral palsy should undergo early prospective cervical evaluations looking for impending cord compromise. When surgery is indicated, circumferential surgery offers the maximal degree of cord decompression and stabilization with the highest rate of fusion.     

Anterior and posterior stabilization of the spine following vertebral body resection. A postmortem investigation

Postmortem examination of a spine, which had been instrumented anteriorly at one level and posteriorly at another following vertebral body resections, showed that the posterior instrumentation was more effective in resisting torsion. Postmortem examination of a second case, where the anterior fixation had been strengthened by the addition of cement studs in the vertebral end-plates and a paravertebral modified and strengthened Zielke screw/rod system, showed this second anterior system to be an improvement for resisting torsion following the resection of one vertebral body. Anterior interbody devices become enveloped in a firm smooth fibrous capsule. A preliminary experiment on a cadaver spine had shown that anterior interbody fixation was better than posterior instrumentation for resisting flexion-compression forces.     

Transoral fusion with internal fixation in a displaced hangman's fracture

STUDY DESIGN: A case is reported in which late displacement of a "hangman's fracture" was managed by transoral C2-C3 fusion by using bicortical iliac crest graft and a titanium cervical locking plate. OBJECTIVES: To review the management of unstable fractures of the axis and to study other reports of transoral instrumentation of the cervical spine. SUMMARY OF BACKGROUND DATA: Undisplaced fractures of the axis are considered to be stable injuries. Although late displacement is unusual, it can lead to fracture nonunion with persisting instability and spinal cord dysfunction. In this situation, an anterior fusion of the second and third cervical vertebrae is preferred to a posterior fusion from the atlas to the third cervical vertebra, which would abolish lateral rotation between C1 and C2. METHODS: The literature on hangman's fractures was reviewed. Clinical and radiographic details of a case of C2 instability were recorded, and the particular problems posed by late displacement were considered. RESULTS: There are no other reports of transoral instrumentation of the cervical spine. A sound fusion of C2-C3 was obtained without infection or other complications. Good neck movement returned by 6 months after surgery. CONCLUSION: Undisplaced fractures of the axis are not always stable. The transoral route allows good access for stabilization of displaced hangman's fractures. In special circumstances, a locking plate may prove useful in securing the bone graft. The cervical spine locking plate can be inserted transorally with no complications and by using standard instrumentation.     

Management of cervical spinal fractures in ankylosing spondylitis with posterior fixation

STUDY DESIGN: Introduction of a posterior approach for internal fixation of fractures of the ankylosed cervical spine. OBJECTIVES: To evaluate the clinical outcome of patients with ankylosing spondylitis and cervical spinal fractures treated with posterior instrumentation and a collar orthosis. SUMMARY OF BACKGROUND DATA: Cervical spinal fractures in patients with ankylosing spondylitis almost always extend completely across the vertebral segment to include both anterior and posterior elements. Treatment with immobilization alone is often inadequate. Generalized spinal rigidity and exaggerated thoracic kyphosis may hinder anterior exposure. Posterior approaches have been described but generally require postoperative halo immobilization. In the authors' technique for patients whose spinal alignment is relatively well preserved, a posterior exposure is used that achieves three-point internal fixation along multiple segments. The complications associated with halo immobilization are avoided. METHODS: Seven patients with ankylosing spondylitis and fractures of the cervical spine were stabilized with posterior instrumentation. Patients were immobilized after surgery with either a cervical collar or a sternal occipital mandibular immobilizing brace and observed for neurologic outcome, radiographic evidence of bony fusion, and complications. RESULTS: No patient experienced neurologic deterioration with surgery. Two patients died at acute rehabilitative facilities after discharge. Radiographic evidence of fusion was observed in the five patients available for follow-up. CONCLUSIONS: Patients with ankylosing spondylitis and cervical spinal fractures can be adequately treated with lateral mass plating and interspinous wiring of autologous rib graft. Adequate postoperative immobilization can be attained with a cervical collar and does not require a halo vest.     

早期前后联合入路治疗下颈椎骨折脱位并脊髓损伤

目的观察前后路一期减压、植骨、内固定治疗脊髓前后方均受压的下颈椎损伤的疗效。方法对本组自2004年1月至2005年12月5例下颈椎骨折脱位并脊髓损伤接受手术治疗的患者,进行回顾性分析。其中后路椎板切除、前路椎间盘切除、植骨颈椎前路钢板内固定术2例;后路椎板切除、前路病椎次全切除、钛网植骨融合钢板内固定术1例;后路椎板切除小关节复位、小关节间植骨侧块钢板内固定术、前路椎间盘切除、植骨术内固定2例。结果脱位均获完全复位,脊髓获得有效减压,椎间植骨6个月后均获骨性融合。4例脊髓功能有不同程度恢复,术中无重要神经、血管、气管及食道损伤,未发生术后消化道应激性溃疡。结论早期前后联合入路治疗下颈椎骨折脱位并脊髓损伤安全、有效。     

Spinal Instrumentation With A Low Complication Rate

Background

Spinal instrumentation has become an increasing part of the armamentarium of neurosurgery and neurosurgical training. For noncontroversial indications for spine fusion the arthrodesis rate seems to be better. For both noncontroversial and controversial indications, the reported complication rate with spinal instrumentation tends to be greater than that with noninstrumented spine surgeries. These reported complications include a 2–3% neurologic injury rate, 3–45% reoperation rate for implant failure, and infection rates of 5–10%. Therefore, we report on 299 cases that have undergone spinal instrumentation placed exclusively by neurosurgeons with a very low complication rate.

Methods

Two hundred ninety-nine consecutive spinal instrumentation cases performed exclusively by neurosurgeons at Indiana University Medical Center were analyzed for complications related to spinal instrumentation. The spinal instrumentation placed consisted of 195 anterior cervical locking plates, 22 cases of posterior cervical instrumentation, 9 cases of combined anterior locking plates with posterior cervical instrumentation, 14 anterior thoraco-lumbar plates, 51 posterior thoraco-lumbar instrumentation cases, and 8 combined anterior/posterior thoraco-lumbar instrumentation cases.

Results

The mean follow-up is 40 months (6–95). There was one perioperative death unrelated to the spinal instrumentation. There were no neurologic injuries and there has been no hardware infection to date. There were two dural tears, three superficial wound infections, and three minor wound breakdowns successfully treated. Hardware complications included three cervical plate/screw extrusions reoperated, one cervical plate fracture reoperated, one posterior cervical screw backout not reoperated, one case of broken pedicle screws not reoperated, one vertebral body failure not reoperated, and one posterior rod case reoperated for excessive rod length and protrusion. The overall complication rate attributable to placement of spinal instrumentation was 10/299 (3%) with a reoperation rate of 2%. The arthrodesis rate was 298/299 (99%).

Conclusion

The complication rate for using spinal instrumentation can be less than previously reported. Lessons learned and discussed should reduce the rate even more. Spinal instrumentation is a safe and useful adjunct to fusion in treating degenerative, traumatic, infectious, and neoplastic diseases of the spine.     

Anterior cervical plating reverses load transfer through multilevel strut-grafts

STUDY DESIGN: In vitro biomechanical study using a programmable testing apparatus that replicated physiologic flexion/extension cervical spine motion and loading mechanics. OBJECTIVE: To determine the influence of anterior plating on multilevel cervical strut-graft mechanics in vitro. SUMMARY OF BACKGROUND DATA: The addition of anterior instrumentation does not prevent construct failure in multilevel cervical corpectomy. METHODS: Six fresh human cadaveric cervical spines (C2-T1) were tested in the four following sequential conditions: harvested, C4-C6 corpectomy, strut-grafted, and strut-grafted with an anterior cervical plate. A force-sensing strut-graft was used to measure compression/tension, flexion/extension and lateral bending moments, and axial torsion. Parameters of stiffness, vertebral motion, and strut-graft loads were compared to determine differences between the four spine conditions. RESULTS: Application of the anterior plate significantly increased the global stiffness (P < 0.01) and decreased the local motion (P < or = 0.01) of the instrumented levels (C3-C7). Flexion of the strut-grafted spine loaded the strut-graft, whereas extension unloaded the strut-graft. With the anterior plate, flexion of the plated spine unloaded the strut-graft. Extension significantly loaded the strut-graft more than similar degrees of flexion in the strut-grafted condition (P = 0.01). Strut-graft loading end limits of 225 N were reached with a mean 7.5 degrees extension in the plated spines. CONCLUSIONS: Anterior multilevel cervical plating effectively increases stiffness and decreases local cervical motion after corpectomy. However, anterior cervical plating also reverses graft loads and excessively loads the graft in extension, which may promote pistoning and failure of multilevel constructs.