Multilevel Corpectomy Research Articles

4:51138. Laminoplasty versus Multilevel Corpectomy in the Treatment of Cervical Spondylytic Myelopathy

4:51138. Laminoplasty versus Multilevel Corpectomy in the Treatment of Cervical Spondylytic Myelopathy

Efficacy and safety of the use of titanium mesh cages and anterior cervical plates for interbody fusion after anterior cervical corpectomy

Background To determine the safety and effectiveness of the use of titanium mesh cages (TMCs) and anterior cervical plates (ACPs) for interbody fusion after anterior cervical corpectomy. Methods From June 2001 to June 2003, 15 patients underwent reconstruction with TMCs and ACPs for interbody fusion after anterior cervical corpectomy in our hospital. The mean follow-up is 13.6 months (range, 9-24 months). Subjects included those with cervical degenerative, traumatic, or pathological diseases. Titanium mesh cages were filled with autologous bone grafts taken from the corpectomy and iliac crest bone chips and were all filled with triosite (calcium phosphate ceramics). The patients' observable signs, neurological reconstruction results, and complications were fully and explicitly recorded throughout the procedure. Radiological imaging studies for measurements of coronal and sagittal angles, sagittal displacements, and settling ratio changes were performed to evaluate spinal stability. We used axial cervical computed tomography (CT) and reconstructive sagittal cervical CT to demonstrate interbody fusion within titanium mesh. Results The alleviation and frequent disappearance of the subjects' original symptoms and the significant neurological recovery obvious in most patients indicated that postoperative spinal stability could be well maintained. No significant differences in mean cage height–related settling rates, mean sagittal displacements, and mean coronal and sagittal angle changes were observed between 1-level and multilevel corpectomy. All patients who received axial and reconstructive sagittal cervical CT scan could demonstrate true interbody fusion within TMC, and no nonunions were present. Cage malplacement was observed in one subject who had neck pain and neck stiffness, rather than from radiculopathy or myelopathy. One subject died of acute myocardial infarction. There were no ceramic-related complications. Conclusions Based on preliminary findings from this study, reconstruction involving TMC interbody fusion with ACP fixation after anterior cervical corpectomy serves as an effective and safe method for the treatment of cervical disease.

Expandable cylindrical cages in the cervical spine: a review of 22 cases

Expandable cylindrical cages (ECCs) have been utilized successfully to reconstruct the thoracic and lumbar spine. Their advantages include ease of insertion, reduced endplate trauma, direct application/maintenance of interbody distraction force, and one-step kyphosis correction. The authors present their experience with ECCs in the reconstruction of the cervical spine in patients with various pathological conditions. Data obtained in 22 patients were reviewed retrospectively. A standard anterior cervical corpectomy was performed in all cases. Local vertebral body bone was harvested for use as graft material. Patients underwent pre- and postoperative assessment involving the visual analog scale (VAS), Nurick grading system for determining myelopathy disability, and radiographic studies to determine cervical kyphosis/lordosis and cage subsidence. Fusion was defined as the absence of motion on flexion-extension x-ray films. Sixteen patients presented with spondylotic myelopathy, two with osteomyelitis, two with fracture, one with tumor metastasis, and one with severe stenosis. Fourteen patients underwent supplemental posterior spinal fusion, seven underwent single-level corpectomy, and 15 patients underwent multilevel corpectomy. No perioperative complications occurred. The mean follow-up period was 22 months. In 11 patients with preexisting kyphosis (mean deformity +19 degrees), the mean correction was 22 degrees. There was no statistically significant difference in subsidence between single- and multilevel corpectomy or between 360 degrees fusion and anterior fusion alone. The VAS scores improved by 35%, and the Nurick grade improved by 31%. The fusion rate was 100%. The preliminary results support the use of ECCs in the cervical spine in the treatment of patients with various disease processes. No significant subsidence was noted, and pain and functional scores improved in all cases. Expandable cylindrical cages appear to be well suited for cervical reconstruction and for correcting sagittal malalignment.

Intraoperative Somatosensory Evoked Potential Monitoring During Cervical Spine Corpectomy Surgery

Retrospective review. To review consecutive cases of cervical spine corpectomy surgery performed with intraoperative somatosensory-evoked potential (SSEP) monitoring. There is controversy about the utility of SSEP monitoring during anterior cervical spine surgery. There is no study in the literature that has specifically evaluated the utility of SSEP monitoring for cervical spine corpectomy surgery. Intraoperative SSEP tracings for 508 patients (average age, 55.7 years; 268 male, 240 female) who underwent anterior cervical fusion with single-level or multilevel corpectomies were reviewed. Intraoperative and postoperative records were analyzed to determine if any new neurologic deficits developed when the patients woke up from anesthesia. The overall incidence of a new postoperative neurologic deficit in this series of patients was 2.4% (11 with nerve root injury, 1 with quadriplegia). The incidence of significant SSEP changes was 5.3% (27 of 508 patients). The most common identifiable cause of SSEP changes was hypotension, and the most common neurologic deficit was deltoid (C5) weakness. One patient had irreversible SSEP changes, and he woke up with new-onset quadriplegia. The calculated sensitivity and specificity of intraoperative SSEP monitoring for detecting impending or resultant intraoperative iatrogenic neurologic injury were 77.1% and 100%, respectively. However, if the isolated nerve root injuries are removed from the analysis, then both the calculated sensitivity and the negative predictive values were 100%. Intraoperative SSEP monitoring can alert the surgeon to adverse iatrogenic intraoperative events with potential for neurologic injury. Most SSEP signal changes are reversible and do not result in a clinical deficit. Isolated nerve root injury appears to be the most common iatrogenic intraoperative injury during cervical spine corpectomy surgery.

Early Failures Following Cervical Corpectomy Reconstruction With Titanium Mesh Cages and Anterior Plating

Retrospective case series. To evaluate the use of titanium mesh cages in the reconstruction of the cervical spine following corpectomy. Previous studies have shown high successful fusion rates and low failure rates with this technique. Similar reconstruction techniques using anterior strut bone grafting and anterior plating have shown higher failure rates following multilevel corpectomies. A retrospective review was performed of 23 consecutive patients who underwent anterior cervical corpectomy reconstructed with a titanium mesh cage, local autograft, and fixed anterior plating. Medical records and radiographs were reviewed. Average follow-up was 28 months. Seven patients (30%) had reconstruction failures. There was 1 failure (6%) in the 1-level corpectomy group and 6 (75%) in the multilevel corpectomy group. All failures occurred before 12 weeks after surgery. The remaining patients had successful fusion (70%). There is a high early failure rate (75%) with the use of a titanium mesh cage and fixed anterior plating for reconstruction of multilevel corpectomies. Posterior fusion and instrumentation should be considered when using this technique for multilevel reconstructions.

Indications and techniques for anterior cervical plating

Anterior cervical plating is commonly performed to stabilize anterior cervical fusions. Modern plating options include dynamic plates, with screws that can either toggle within fixed holes or translate within slotted holes. Regardless of the plating system used, paramount to success and avoidance of complications with plated anterior cervical fusions are meticulous plating techniques, exacting graft carpentry, and understanding the biomechanical limitations of plating in certain situations, such as multilevel corpectomies reconstructed with a single-strut graft. In order to prevent graft-related complications associated with long-strut grafts, additional posterior fixation and fusion, or alternative corpectomy constructs, such as multilevel anterior cervical discectomy and fusion, corpectomy-discectomy, and corpectomy-corpectomy, should be considered instead if the pattern of stenosis allows.

Late Stress Fracture of a Well-Incorporated Autologous Fibula Strut Graft in the Cervical Spine

Four-level corpectomy for cervical spondylotic myelopathy presents special challenges to successful outcomes. At our institution, where the senior author has performed over 300 multilevel corpectomies with autologous fibula reconstruction, only 11 four-level procedures have been performed. It is important to consider the length of time required for complete revascularization of these long strut grafts as well as unusual postural or gait biomechanics the patient may have. Patients with altered gait or trunk stability who require anterior surgery for cervical spondylotic myelopathy may be best served by concurrent posterior fusion. We report a case in which a patient with cervical spondylotic myelopathy and diplegic cerebral palsy developed a stress fracture in the midportion of his well-incorporated autologous fibula strut graft 1 year after it was placed following four-level corpectomy.

Fusion rate: a time-to-event phenomenon.

The term "fusion rate" is generally denoted in the literature as the percentage of patients with successful fusion over a specific range of follow up. Because the time to fusion is a time-to-event phenomenon a more accurate method of representation may be made using the Kaplan-Meier method of estimation. The current study was performed to illustrate that fusion rate is more accurately represented by median times as calculated using survival analysis. Patients undergoing a cervical decompressive corpectomy and reconstruction formed the basis of the primary analysis. A secondary analysis was made to evaluate the difference in the fusion times for one- compared with multilevel corpectomy cases. Data were collected at a tertiary care institution over a 5-year period with 6-month follow up after the last recruitment. Descriptive statistics of baseline patient characteristics, the extent of disease, and the surgical intervention were obtained. Fusion was the final outcome, and it was defined as the "event." The presence of any trabeculae bridging between the vertebral body and allograft signified the occurrence of an event. Postoperative static radiographs were evaluated by independent neuroradiologists to assess the presence of fusion. Fusion rate was determined using the Kaplan-Meier estimate. The median time to fusion was calculated, as were the 95% confidence intervals (CIs). These were stratified for patients who underwent one- and two-level vertebrectomy. The log-rank test was used to differentiate between one-level and multilevel corpectomy. Multivariate analysis was performed using Cox regression for further evaluation, by adjusting for covariates (age, sex, smoking history). Fifty-seven patients underwent single- or multilevel corpectomy and fusion. The male/female ratio was similar, with a median age of 53 years. Fourteen patients had a history of cigarette smoking. Thirty-six patients underwent a one-level corpectomy, 20 a two-level corpectomy, and one patient underwent a three-level corpectomy. The analysis was restricted to one- and two-level cases. The median time to fusion for the cephalad and caudad aspect of the graft-host interface was 88 days (95% CI 82-94 days) and 85 days (95% CI 77-93 days), respectively. As generally reported in the literature, this translates to a 92% (by 2.1 years) and 93% (by 1.5 years) fusion rate, for the cephalad and caudad, respectively. The median time to fusion for the cephalad aspect of the graft for one-level vertebrectomy was 87 days (95% CI 83-91 days), whereas for two-level vertebrectomy was 90 days (95% CI 59-121 days). The median time to fusion for the caudal aspect of the graft-host interface was 85 days (95% CI 80-90 days) for one-level corpectomy and 90 days (95% CI 83-97 days) for the two-level cases. There was no statistically significant difference in the median time to fusion for one- and two-level corpectomy at either the superior or inferior aspect of the graft (p = 0.19 and 0.84, respectively). This held true even after adjusting for covariates. Fusion rate is a time-to-event phenomenon and is more accurately represented using the Kaplan-Meier method of estimation.

Enhancement of stability following anterior cervical corpectomy: a biomechanical study.

An in vitro biomechanical study of various reconstructive techniques following decompression of the spondylotic cervical spine. OBJECTIVE.: To evaluate the biomechanical stability of anterior cervical plate fixation following three strategies of decompression for multilevel cervical spondylosis (three levels) of the cervical spine: three level discectomy, single corpectomy and discectomy, and a two-level corpectomy. The main goals of surgical treatment for cervical myelopathy include adequate decompression and stabilization while maintaining or restoring cervical lordosis. Cervical decompression is often performed through a corpectomy followed by strut-graft reconstruction. An anterior cervical plate with end-fixation (two points of fixation) is then used to span the construct. The authors propose an alternative to multilevel corpectomy and long-segment end construct plate fixation. Often times, the cervical stenosis is confined to the area of the degenerative discs. As a result, the authors feel that either multilevel discectomy or a corpectomy combined with discectomy followed by segmental plate fixation may provide adequate decompression with increased biomechanical rigidity as compared to cervical plate-constructs with end-fixation only. Seven human cadaveric fresh-frozen cervical spines from C1-T1 were utilized. Three-dimensional motion analysis with an optical tracking device was used to determine motion following various reconstruction methods. All seven cervical spines underwent testing in a randomized order. The end construct model consisted of a corpectomy at C4 and C5 with a polymethyl methacrylate strut graft and an anterior cervical PEAK (DePuy-AcroMed) plate. The two segmental constructs also utilized the PEAK plate with one construct undergoing discectomies at C3-C4, C4-C5, and C5-C6 with polymethyl methacrylate interbody grafts and the other segmental construct undergoing a discectomy at C3-C4 and a corpectomy of C5. All specimens underwent a pure moment application of 2 Nm with regards to flexion-extension, lateral bending, and axial rotation. RESULTS.: The three-level discectomy and combined one-level discectomy and corpectomy with segmental fixation was significantly more rigid in flexion-extension and lateral bending than the two-level corpectomy with end-construct plate fixation (P < 0.05). There was no increase in stability during extension between the end construct (two-level corpectomy) reconstruction model and the un-instrumented corpectomy and grafted specimen. No difference was noted between the segmental constructs and the end-construct with regards to axial rotation. Cervical myelopathy is traditionally treated with a multilevel corpectomy and an end-construct plate fixation spanning the strut graft. A large moment arm is generated at the ends of the construct, potentially leading to plate migration or dislodgment. Often times, adequate decompression can be achieved with either a multilevel discectomy or a combined discectomy and corpectomy with segmental plate fixation. This study clearly demonstrates that segmental plate fixation affords a more biomechanically rigid method of reconstruction with regards to flexion-extension and lateral bending than end-construct plate fixation. The increased rigidity afforded by segmental fixation may significantly decrease the likelihood of plate dislodgement in the setting of anterior instrumentation alone following anterior alone, long segment reconstruction procedures.

Biomechanical Comparison of Cervical Spine Reconstructive Techniques After a Multilevel Corpectomy of the Cervical Spine

An in vitro biomechanical study of several reconstructive techniques after a two-level cervical corpectomy. To evaluate, compare, and quantitate the stability of several reconstructive strategies (anterior, posterior, or anterior/posterior with or without instrumentation) after a multilevel cervical corpectomy. Several clinical and biomechanical studies have questioned the stability of stand-alone long-segment anterior plate fixation after a multilevel (>or=2) corpectomy. The large cantilever forces generated within the stabilized construct, particularly at the caudal screw-bone interface, have led to plate and screw dislodgement and the need for further surgical intervention. The addition of posterior segmental instrumentation has been shown to improve overall stability and decrease local stresses on the anterior fusion construct (graft and plate). Seven fresh-frozen cadaveric human cervical spines (C1-T1) were harvested. The C1-C2 and C7-T1 vertebral bodies were embedded in poly-methylmethacrylate (PMMA). Three VICON cameras tracked three-dimensional segmental motions at the ends of the fusion construct after a two-level corpectomy and placement of a strut graft with or without instrumentation. Pure moments (flexion/extension, lateral bending, and axial rotation) were applied to the C1 level of each specimen. The motion segments were loaded to a maximum of 2 Nm using dead weights. Testing was first performed on the intact specimens. Then, a two-level corpectomy at the C4 and C5 levels was performed. A PMMA strut graft was then placed into the corpectomy site. Biomechanical testing was then repeated among three different reconstruction techniques: 1) anterior cervical locking plate (PEAK; Depuy-Acromed, Raynham, MA) with dual unicortical screw fixation at C3 and C6; 2) posterior cervical instrumentation (Summit; Depuy-Acromed) using a 3.0-mm rod with segmental lateral mass screw fixation from C3 to C6; and 3) a combined anterior-posterior instrumentation using the anterior PEAK plate and posterior Summit rod system. In all pure moments tested (flexion/extension/lateral bending/axial rotation) the combined anterior-posterior instrumentation reconstruction model and the posterior-only instrumentation model were significantly more rigid than the anterior-only instrumentation model (P < 0.05). Interestingly, no statistically significant difference was noted between the combined anterior plate/posterior instrumentation model and the posterior instrumentation-only model. The biomechanical results obtained suggest that posterior segmental instrumentation confers significant stability to a multilevel cervical corpectomy regardless of the presence or absence of anterior instrumentation. In cases in which the stability of a multilevel reconstruction procedure is tenuous, the surgeon should strongly consider the placement of segmental posterior instrumentation to significantly improve the overall stability of the fusion construct.

15. Steroids for multi-level cervical corpectomy procedures: do they reduce upper airway edema? A randomized, prospective, double-blind study

15. Steroids for multi-level cervical corpectomy procedures: do they reduce upper airway edema? A randomized, prospective, double-blind study

Difficult Problems in Cervical Spine Surgery

Dr. Wolfla has met the challenge of compiling a unique and concise collection on difficult problems of the cervical spine. Topics such as multilevel corpectomies, sports injuries, ossification of the posterior longitudinal ligament, kyphotic deformities, options for failed anterior cervical fusion (to name only a few) are rarely found in more traditional texts. We are fortunate to have this compendium for Seminars and appreciate the efforts of Dr. Wolfla and his contributors.

Partial Corpectomy for Cervical Spondylosis

A retrospective review was performed of a single surgeon's experience with partial corpectomy over a 9-year period. The measures evaluated included fusion rate, complications, and neurologic symptoms. To demonstrate the safety and efficacy of partial corpectomy for multilevel cervical spondylosis. Strategies for the surgical management of cervical spondylosis have included laminectomy, multilevel corpectomy, and multilevel discectomy. All have significant disadvantages, including high nonunion rates and late deformity. A procedure incorporating multilevel discectomy, partial corpectomy, strut graft, and plating is described. By removal of the anterior two thirds of the intervening vertebral body, visualization of the interface between the dura and the disc or PLL is enhanced, and osteophytes can be easily removed. Fusion rates are improved. All partial corpectomy cases with a 2-year follow-up evaluation managed by the senior author for multilevel cervical spondylosis from 1991 to June 1999 were reviewed for the number of levels decompressed, graft source, use of plating, fusion success, and neurologic status. Most of the patients (n = 97) were managed with two-level discectomies, with 42 requiring treatment of three levels and 5 requiring treatment of four or more levels. Allograft was used in 60%. The remainder received iliac crest bone graft. The majority (81%) were plated. Of the cases with 2-year follow-up evaluation, the fusion rate was 95.8%, independent of the number of levels fused. Among the 11% who had continued problems, most had improved. Nonunions were higher in smokers. Partial corpectomy is an effective strategy for treating multilevel cervical disc disease. It is associated with a high fusion rate. In addition, partial corpectomy facilitates a complete decompression by providing excellent visualization of the dural interface.

Multilevel Corpectomy for Cervical Spondylotic Myelopathy

Multilevel Corpectomy for Cervical Spondylotic Myelopathy

Corpectomies versus laminoplasty for multilevel cervical myelopathy: an independent matched cohort analysis

Charles C. Edwards, II, MD, Atlanta, GA, USA; John Heller, MD, Hidecki Morikami, Decatur, GA, USAIntroduction: The treatment of choice for multilevel cervical myelopathy remains a matter of investigation. For the decompression of three or more motion segments, multilevel corpectomies and laminoplasty have proven effective while avoiding the pitfalls of laminectomy. Direct clinical comparisons of these two procedures are few in number and limited by the heterogeneity in their patient groups. The purpose of this study is to compare the clinical and radiographic outcomes of corpectomy and laminoplasty using an independent matched-cohort analysis.Methods: Medical records of all patients treated for multilevel cervical myelopathy with either corpectomy or laminoplasty between 1992 and 1999 at our institution were reviewed. Thirty-four corpectomy and 51 laminoplasty patients fulfilled stringent inclusion and exclusion criteria. From this pool of eligible patients, 13 patients who underwent corpectomy were blindly matched with 13 patients that underwent laminoplasty based on known prognostic criteria. A single physician independently evaluated each patient and their radiographs at their latest follow-up appointment.Results: The cohorts were well matched by age, duration of symptoms, severity of myelopathy (Nurick grade), canal stenosis and preoperative sagittal alignment (C2–C7). The mean operative time, blood loss and hospital stay were nearly identical. The mean follow-up for corpectomy and laminoplasty were 3.7 and 3.0 years, respectively. Laminoplasty patients showed greater neurologic improvement (Nurick score 1.5 versus 1.0). Subjective improvements in strength, dexterity, sensation, pain and gait were similar for the two operations. The prevalence of axial discomfort at latest follow-up was the same for each cohort, but the analgesic requirements were greater for patients who underwent corpectomy. Sagittal motion from C2 to C7 decreased by 57% after corpectomy and by 46% after laminoplasty. One complication (transient C5 palsy) occurred in the laminoplasty group. Corpectomy complications included progression of myelopathy (one), persistent dysphagia (four), persistent dysphonia (two), significant subjacent disc degeneration (two) and nonunion (one).Conclusion: Corpectomy and laminoplasty reliably arrest myelopathic progression in multilevel cervical myelopathy and can lead to significant neurologic recovery and pain reduction in a majority of patients. The laminoplasty cohort required less pain medication at final follow-up than did the corpectomy patients. Given this and the higher prevalence of complications among corpectomy patients, we believe that laminoplasty may be the preferred treatment for multilevel cervical myelopathy in the absence of preoperative kyphosis.

Cervical spine multilevel decompression/reconstruction with anterior/posterior internal fixation

Cervical spine multilevel decompression/reconstruction with anterior/posterior internal fixation

Early results using the Atlantis anterior cervical plate system

The authors present a retrospective review of 77 patients in whom they performed anterior cervical discectomy and fusion (ACDF) in the treatment of radiculopathy and/or myelopathy. In all cases anterior interbody fusion was performed using the Atlantis locking plate system to treat the degenerative disease. There were 41 men and 36 women (mean age 53.8 years), and 24 active cigarette smokers (31%) in the group. All patients presented with signs and symptoms of cervical radiculopathy and/or myelopathy, and magnetic resonance imaging or computerized tomography myelography demonstrated evidence of radicular and/or spinal cord compression at one or more cervical levels. Thirty-one patients underwent single-level ACDF, 20 patients underwent multilevel ACDF without posterior instrumentation, in eight patients one- to four-level corpectomies were supplemented with posterior fixation, 12 patients underwent single-level corpectomy, and six patients underwent multilevel corpectomy with no posterior instrumentation. The mean follow-up period was 15.33 months; overall good-to-excellent outcome was seen in 75% of patients; osseous fusion was demonstrated in 93.5%. In all patients except three, fibular allograft was used as graft material. The degree of overall cervical lordosis was measured at the last follow up and was compared with normal values obtained in age-matched individuals. In addition, the degree of cervical lordosis at fusion levels was compared with overall cervical lordosis. In patients in all five of the aforementioned categories significantly less lordosis was demonstrated than in age-matched controls. In patients who underwent single-level ACDF, single-level corpectomy, and multilevel ACDF significantly less lordosis was observed at the fusion segment than that in the overall cervical spine. Complications included one episode of chronic anterior wound drainage treated with intravenous antibiotic medication and one postoperative posterior wound infection, which required reoperation and intravenous antibiotic medication. Two cases (2.6%) of anterior screw backout and/or breakage were identified. One patient died of unrelated causes within 3 months of operation. These initial results indicate that use of the Atlantis plate system for anterior cervical arthrodesis produces fusion rates and clinical outcomes that are comparable with those obtained using other locking plating systems. It has the unique advantage, however, of providing the surgeon with the choice of fixed, variable, or hybrid screw constructs as a way of tailoring screw angles to individual anatomical/biomechanical needs.

Stabilizing potential of anterior cervical plates in multilevel corpectomies.

An in vitro investigation of three-dimensional kinematics of cervical spine models of one- and three-level corpectomy with anterior plate fixation. To evaluate the capability of an anterior plate to stabilize the reconstructed cervical spine under simulated physiologic motions, and to study the effects of fatigue loading. Clinical studies have found high failure rates of multilevel anterior cervical plate fusions, indicating suboptimal stabilization. However, no biomechanical studies have been done to investigate the stabilizing capabilities of long-plate instrumentations in corpectomy models. Seven fresh human cadaveric cervical spine specimens (C2-T1) were used. Flexibility tests consisted of flexion, extension, and bilateral torsion, and lateral bending, each with a pure moment of 0.25, 0.5, 0.75, and 1.0 Nm. Stabilizing potential indices [(MotionIntact-MotionInstrumented)/MotionIntact] for ranges of motion and neutral zones obtained from the flexibility tests, were measured when the specimen was intact and after one-level (C5) and three-level (C4, C5, and C6) corpectomies and anterior plate stabilizations). The stabilizing potential indices were re-measured after a 1000-cycle fatigue loading (1 Nm flexion and extension moments at C5 vertebra at 0.14 Hz). The differences in stabilizing potential indices of range of motion and neutral zone between one-level and three-level plates were not significant before fatigue. However, after fatigue, the stabilizing potential indices significantly decreased (P < 0.05) for the three-level model, but not for the one-level plate model. The capability of an anterior cervical plate to stabilize the spine after three-level corpectomy was significantly reduced with fatigue loading.

Reconstruction after multilevel corpectomy in the cervical spine. A sagittal plane biomechanical study.

An in vitro biomechanical study of reconstruction techniques used after multilevel cervical corpectomy. To determine the biomechanical behavior of the cervical spine after a multilevel corpectomy and reconstruction with a strut graft and supplementation of the graft with anterior and posterior plates. Reconstruction of the spine after multilevel corpectomy represents a significant challenge, with nonunion or graft dislodgment being relatively common. Anterior and posterior plate fixation have increased the possibilities for supplemental stabilization. Although some clinical studies have been performed to examine multilevel corpectomies reconstructed with plates, biomechanical studies are few and are limited to single-segment models. Flexibility testing was performed on 11 intact cervical spine preparations. Flexibility testing was also conducted on the spine preparations after reconstruction with a strut graft, after supplementation of the graft with an anterior plate, and after supplementation of the graft with lateral mass plates. Physiologic moments were applied dynamically, and the three-dimensional motion of the specimen was recorded with stereophoto-grammetry. Failure testing was performed on the plated specimens in compression. Load displacement curves and failure modes were analyzed. The range of motion after reconstruction compared with the control was decreased 24% after strut grafting, 43% after application of an anterior plate, and 62% after application of posterior plates. Similarly, flexibility coefficients showed that the posterior plate technique was the least flexible, followed by the anterior plate technique, with the graft alone being the most flexible reconstruction construct. Load to initial failure tended to be higher in posterior than in anterior plate specimens, and screw pullout was the predominant failure mode. The application of plates to the cervical spine as an adjunct to bone graft may improve the surgeon's ability to stabilize the spine after multilevel corpectomy. Understanding the biomechanics of these devices and the potential mode of failure is important in their use.

Anterior Subaxial Decompression for Cervical Spondylotic Myelopathy

Decompression of the subaxial cervical spinal cord in the presence of a cervical kyphosis can be accomplished only by the strategy called multilevel corpectomy. Our experience with >200 such procedures for cervical spondylotic myelopathy indicates that the width of decompression should be limited, whereas the length should be liberal. The routine use of plating and exclusive use of autogenous bone grafts are not usually necessary for acceptable outcomes. Soft-tissue morbidity can be minimal by regular release of retractors, and orthosis in the otherwise stable neck need not be complex.