Andrew Cappuccino

Prospective, randomized, multicenter Food and Drug Administration investigational device exemption study of lumbar total disc replacement with the CHARITÉ artificial disc versus lumbar fusion: Five-year follow-up

BACKGROUND CONTEXT The CHARITE artificial disc, a lumbar spinal arthroplasty device, was approved by the United States Food and Drug Administration in 2004 based on two-year safety and effectiveness data from a multicenter, prospective, randomized investigational device exemption (IDE) study. No long-term, randomized, prospective study on the CHARITE disc or any other artificial disc has been published to date. PURPOSE The purpose of this study was to compare the safety and effectiveness at the five-year follow-up time point of lumbar total disc replacement using the CHARITE artificial disc (DePuy Spine, Raynham, MA) with that of anterior lumbar interbody fusion (ALIF) with BAK cages and iliac crest autograft, for the treatment of single-level degenerative disc disease from L4 to S1, unresponsive to nonoperative treatment. STUDY DESIGN/SETTING Randomized controlled trial-five-year follow-up. PATIENT SAMPLE Ninety CHARITE patients and 43 BAK patients. OUTCOME MEASURES Self-reported measures: visual analog scale (VAS); validated Oswestry disability index (ODI version 1.0); Short-Form 36 Questionnaire, and patient satisfaction. Physiologic measures: radiographic range of motion, disc height, and segmental translation. Functional measures: work status. METHODS Of the 375 subjects enrolled in the CHARITE IDE trial, 277 were eligible for the five-year study and 160 patients thereof completed the five-year follow-up. The completers included 133 randomized patients. Overall success was defined as improvement> or =15 pts in ODI vs. baseline, no device failure, absence of major complications, and maintenance or improvement of neurological status. Additional clinical outcomes included an ODI questionnaire as well as VAS, SF-36, and patient satisfaction surveys. Work status was tracked for all patients. Safety assessments included occurrence and severity of adverse events and device failures. Radiographic analyses such as index- and adjacent-level range of motion, segmental translation, disc height, and longitudinal ossification were also carried out. RESULTS Overall success was 57.8% in the CHARITE group vs. 51.2% in the BAK group (Blackwelders test: p=0.0359, Delta=0.10). In addition, mean changes from baseline for ODI (CHARITE: -24.0 pts vs. BAK: -27.5 pts), VAS pain scores (CHARITE: -38.7 vs. BAK: -40.0), and SF-36 questionnaires (SF-36 Physical Component Scores [PCS]: CHARITE: 12.6 pts vs. BAK: 12.3 pts) were similar across groups. In patient satisfaction surveys, 78% of CHARITE patients were satisfied vs. 72% of BAK patients. A total of 65.6% patients in the CHARITE group vs. 46.5% patients in the BAK group were employed full-time. This difference was statistically significant (p=0.0403). Long-term disability was recorded for 8.0% of CHARITE patients and 20.9% of BAK patients, a difference that was also statistically significant (p=0.0441). Additional index-level surgery was performed in 7.7% of CHARITE patients and 16.3% of BAK patients. Radiographic findings included operative and adjacent-level range of motion (ROM), intervertebral disc height and segmental translation. At the five-year follow-up, the mean ROM at the index level was 6.0 degrees for CHARITE patients and 1.0 degrees for BAK patients. Changes in disc height were also similar for both CHARITE and BAK patients (0.7 mm for both groups, p=0.9827). Segmental translation was 0.4 and 0.8mm in patients implanted with CHARITE at L4-L5 vs. L5-S1, respectively, and 0.1mm in BAK patients. CONCLUSIONS The results of this five-year, prospective, randomized multicenter study are consistent with the two-year reports of noninferiority of CHARITE artificial disc vs. ALIF with BAK and iliac crest autograft. No statistical differences were found in clinical outcomes between groups. In addition, CHARITE patients reached a statistically greater rate of part- and full-time employment and a statistically lower rate of long-term disability, compared with BAK patients. Radiographically, the ROMs at index- and adjacent levels were not statistically different from those observed at two-years postsurgery.

The effect of spinal destabilization and instrumentation on lumbar intradiscal pressure: an in vitro biomechanical analysis.

Study Design. In vitro biomechanical testing was performed in human cadaveric lumbar spines, using pressure needle transducers to analyze the effects of spinal destabilization and instrumentation on lumbar intradiscal pressures. Objectives. To quantify changes in lumbar intradiscal pressures at three adjacent disc levels under conditions of spinal reconstruction, and to evaluate the possibility of pressure‐induced disc pathology secondary to spinal instrumentation. Summary of Background Data. Lumbar intradiscal pressures under in vivo and in vitro conditions and the use and development of spinal instrumentation have been investigated comprehensively. However, the effects of spinal destabilization and instrumentation on lumbar intradiscal pressure have not been delineated clearly. Methods. In 11 human cadaveric lumbosacral specimens, specially designed pressure needle transducers quantified intradiscal pressure changes at three adjacent disc levels (L2‐L3, proximal; L3‐L4, operative; and L4‐L5, distal) under four conditions of spinal stability: intact, destabilized, laminar hook and pedicle screw reconstructions. Biomechanical testing was performed under axial compression (0‐600 N), anterior flexion (+12.5°) and extension (−12.5°), after which the level of degeneration and disc area (cm2) were quantified. Results. In response to destabilization and instrumentation, proximal disc pressures increased as much as 45%, and operative pressure levels decreased 41‐55% (P < 0.05), depending on the instrumentation technique. Linear regression and correlation analyses comparing intradiscal pressure to the grade of disc degeneration were not significant (r = 0.24). Conclusions. Changes in segmental intradiscal pressure levels occur in response to spinal destabilization and instrumentation (P < 0.05). Intradiscal cyclic pressure differentials drive the metabolic production and exchange of disc substances. Conditions of high or low disc pressure secondary to spinal instrumentation may serve as the impetus for altered metabolic exchange and predispose operative and adjacent levels to disc pathology.

Minimally Invasive Spine Surgery

Paul C. McAfee, MD, MBA, Frank M. Phillips, MD, Gunnar Andersson, MD, PhD, Asokumar Buvenenadran, MD, Choll W. Kim, MD, Carl Lauryssen, MD, Robert E. Isaacs, MD, Jim A. Youssef, MD, Darrel S. Brodke, MD, Andrew Cappuccino, MD, Behrooz A. Akbarnia, MD, Gregory M. Mundis, MD, William D. Smith, MD, Juan S. Uribe, MD, Steve Garfin, MD, R. Todd Allen, MD, William Blake Rodgers, MD, Luiz Pimenta, MD, PhD, and William Taylor, MD

Biomechanical Analysis and Review of Lateral Lumbar Fusion Constructs

Study Design. Biomechanical study and the review of literature on lumbar interbody fusion constructs. Objective. To demonstrate the comparative stabilizing effects of lateral interbody fusion with various supplemental internal fixation options. Summary of Background Data. Lumbar interbody fusion procedures are regularly performed using anterior, posterior, and more recently, lateral approaches. The biomechanical profile of each is determined by the extent of resection of local supportive structures, implant size and orientation, and the type of supplemental internal fixation used. Methods. Pure moment flexibility testing was performed using a custom-built 6 degree-of-freedom system to apply a moment of ±7.5 Nm in each motion plane, while motion segment kinematics were evaluated using an optoelectronic motion system. Constructs tested included the intact spine, stand-alone extreme lateral interbody implant, interbody implant with lateral plate, unilateral and bilateral pedicle screw fixation. These results were evaluated against those from literature-reported biomechanical studies of other lumbar interbody constructs. Results. All conditions demonstrated a statistically significant reduction in range of motion (ROM) as a percentage of intact. In flexion-extension, ROM was 31.6% stand-alone, 32.5% lateral fixation, and 20.4% and 13.0% unilateral and bilateral pedicle screw fixation, respectively. In lateral bending, the trend was similar with greater reduction with lateral fixation than in flexion-extension; ROM was 32.5% stand-alone, 15.9% lateral fixation, and 21.6% and 14.4% unilateral and bilateral pedicle screw fixation. ROM was greatest in axial rotation; 69.4% stand-alone, 53.4% lateral fixation, and 51.3% and 41.7% unilateral and bilateral pedicle screw fixation, respectively. Conclusion. The extreme lateral interbody construct provided the largest stand-alone reduction in ROM compared with literature-reported ALIF and TLIF constructs. Supplemental bilateral pedicle screw-based fixation provided the overall greatest reduction in ROM, similar among all interbody approach techniques. Lateral fixation and unilateral pedicle screw fixation provided intermediate reductions in ROM. Clinically, surgeons may evaluate these comparative results to choose fixation options commensurate with the stability requirements of individual patients.

The Effects of Spinal Fixation and Destabilization on the Biomechanical and Histologic Properties of Spinal Ligaments: An in Vivo Study

Study Design. An animal study was conducted to assess whether different surgical procedures of spinal fixation and destabilization would influence the biomechanics and histology of lumbar spinal ligaments. Objectives. To investigate the effects of spinal fixation and destabilization as well as surgical intervention itself on the biomechanical and histologic properties of lumbar spinal ligaments. Summary of Background Data. Although several investigators have reported normal biomechanical properties of different spinal ligaments, there have been no studies in which changes in spinal ligament properties, secondary to the altered biomechanical environment provided by such surgical procedures as spinal fixation and destabilization, have been investigated. Methods. Thirty‐six mature sheep were divided into four groups: Group I: nonsurgical control; Group II: sham operation consisting of bilateral posterolateral exposure at L4‐L5; Group III: spinal fixation using transpedicular screws and plates and bilateral posterolateral bone graft at L4‐L5; and Group IV: spinal destabilization consisting of bilateral facetectomy and anterior discectomy at L4‐L5. Four months after surgery, the biomechanical analysis included destructive tensile testing of four different bone‐ligament‐bone complexes at the operative and proximal adjacent levels: anterior longitudinal ligament, posterior longitudinal ligament, ligamentum flavum, and supraspinous and interspinous ligaments combined. Histomorphometric analyses of the vertebral body and spinal ligaments were performed histomorphometrically. Results. Biomechanical analysis results demonstrated remarkable changes in the structural and mechanical ligament properties at the operative level. The fixation groups ligaments showed consistent decreases in the ultimate load and elastic modulus compared with those parameters in the control group (P < 0.05). Histologically, the fixation groups ligamentum flavum showed marked vacuolation in the ligament substance, whereas the interspinous ligament exhibited significant insertion changes compared with little change in substance. In all eight sheep in Group IV, unintentional bilateral facet fusions were obtained; and in all eight animals in Group III with pedicle instrumentation and posterolateral fusion, solid arthrodesis was exhibited. This allowed a distinction to be made between the stress‐shielding effect of spinal instrumentation and arthrodesis (Group III) versus spinal fusion alone (Group IV) on both spinal ligament and vertebral body. Group II (sham) had a significant decrease in supraspinous and interspinous ligaments, but nonsignificant decreases in the stress‐shielding effect of 10‐12% in other ligaments. Conclusions. Posterior spinal instrumentation and fusion led to decreased biomechanical properties of the ligamentum flavum, posterior longitudinal ligament, and interspinous and supraspinous ligaments. The stress‐shielding effects were ligament dependent and were most pronounced on the posterior side. The altered biomechanical environment produced by spinal fixation, surgical intervention itself, or nonphysiologic mobilization can affect the ligamentous properties in vivo, possibly serving as the impetus for low back pain.

A prospective, randomized, controlled clinical investigation comparing PCM cervical disc arthroplasty with anterior cervical discectomy and fusion. 2-year results from the US FDA IDE clinical trial.

Study Design. Prospective, multicenter, randomized Food and Drug Administration approved investigational device exemption clinical trial. Objective. To evaluate the safety and effectiveness of the PCM Cervical Disc compared with anterior cervical discectomy and fusion (ACDF) in the treatment of patients with degenerative spondylosis and neurological symptoms at 1 level between C3–C4 and C7–T1. Summary of Background Data. Cervical disc arthroplasty in the treatment of symptomatic cervical spondylosis has been studied in other series. The PCM Cervical Disc is a nonconstrained motion-sparing alternative to ACDF. Methods. Patients 18 to 65 years of age with single-level symptomatic cervical spondylosis with radiculopathy and/or myelopathy unresponsive to nonoperative treatment were enrolled, including patients with prior nonadjacent or adjacent single-level fusions. The per-protocol patient sample at 2 years included 342 patients (189 PCM, 153 ACDF). Longitudinal outcomes were comparatively evaluated. Results. At 2 years postoperatively, clinical measures—neck and arm pain visual analogue scale, Neck Disability Index (NDI), SF-36, and neurological status—were significantly improved from preoperative baselines in both groups. Mean NDI score at 2 years was significantly lower in PCM group (P = 0.029). There were no statistical differences between groups in rates of surgery-related serious adverse events (5.6% PCM, 7.4% ACDF) or secondary surgical procedures (5.2% PCM, 5.4% ACDF). Patients with PCM reported lower dysphagia scores (8.8/100 vs. 12.1/100; P = 0.045) and higher patient satisfaction (82.8/100 vs. 81.4/100). Overall success, a composite endpoint including minimum 20% NDI improvement, no major complications, no neurological worsening, no secondary surgical procedures, and meeting radiographical criteria of motion for PCM and fusion for ACDF, was significantly greater in the PCM group (75.1% vs. 64.9%; P = 0.020). Conclusion. The treatment of symptomatic single-level cervical spondylosis with PCM achieves clinical outcomes that are at least equivalent to ACDF while maintaining motion. At 2 years, patients with PCM had lower NDI scores, statistically lower rate of prolonged dysphagia, greater patient satisfaction, and superior overall success. Level of Evidence: 1

Lower incidence of dysphagia with cervical arthroplasty compared with ACDF in a prospective randomized clinical trial.

Study Design The current study of 251 consecutive 1-level anterior cervical reconstructions was undertaken to compare the incidence of dysphagia between cervical disk replacement and conventional anterior cervical fusion and instrumentation. Objectives This is a report of 251 patients from 5 investigational centers in the Food and drug Administrations prospective, randomized porous-coated motion (PCM) trial using a validated dysphagia outcomes instrument. The dysphagia data for both PCM and anterior cervical diskectomy and fusion (ACDF) patients were reviewed from 5 centers to (1) compare the severity of dysphagia, (2) compare the postoperative incidence of dysphagia, and (3) to compare the resolution of perioperative dysphagia. Summary of Background Data Dysphagia and dysphonia after anterior surgical approaches to the cervical spine have been previously reported. The current prospective, randomized investigation quantifies clinical dysphagia based on 3 criteria-severity, incidence, and resolution—in a time-course evaluation. Methods Patients between 18 and 65 years with 1-level symptomatic cervical radiculopathy and/or myelopathy for progressive neurologic symptoms, were randomized to undergo anterior decompression and PCM arthroplasty (N=151) or ACDF (control) (N=100). Patients self-reported dysphagia severity using the Bazaz scale preoperatively and at follow-up. The Bazaz scale has 4 classes of severity based upon the problems with swallowing that the patient has with both liquids and solids. Results The Bazaz results demonstrate that although both the PCM and ACDF groups exhibited an initial postoperative problem with swallowing, the PCM group continued to improve with increasing time after implantation, whereas the ACDF only improved minimally. The PCM treatments indicated significantly lower incidence of dysphagia at 3 and 12 months postoperatively compared with ACDF controls (P<0.05). An increase in dysphagia severity at either the 6-week or 3-month follow-up visit was reported in 35 (42%) PCM and 29 (64%) ACDF subjects. Long-term resolution of these symptoms was noted in 74% (26/35) of the PCM subjects as compared with 41.4% (12/29) of the ACDF subjects (P=0.015). Conclusions In a prospective randomized clinical study the incidence of postoperative dysphagia and the long-term resolution of the dysphagia was greatly improved in the PCM group compared with the instrumented ACDF control group.

Video-assisted thoracoscopic surgery versus open thoracotomy for anterior thoracic spinal fusion. A comparative radiographic, biomechanical, and histologic analysis in a sheep model.

Study Design. In this in vivo investigation, a sheep model was used to compare the efficacy of a video‐assisted thoracoscopic approach and a traditional thoracotomy in promoting a successful interbody spinal arthrodesis. Objectives. To compare the incidence of successful anterior spinal arthrodesis among three stabilization techniques‐iliac crest, Bagby and Kuslich device, and Z‐Plate‐performed using a video‐assisted thoracoscopic approach and conventional open thoracotomy approaches. Summary of Background Data. A clinical outcome study on open versus endoscopic spinal fusion is not yet available. Moreover, no basic scientific investigations have been conducted to determine whether the success of an endoscopic arthrodesis is comparable to that of a conventional open procedure. Methods. Fourteen Western Crossbred sheep underwent three identical destabilization procedures at T5‐T6, T7‐T8, and T9‐T10, in which the anterior and middle osteoligamentous columns of the spine were resected, followed by three randomized reconstruction procedures using iliac autograft alone, Bagby and Kuslich device packed with iliac autograft, and Z‐plate stabilization with iliac autograft. In seven sheep, the entire destabilization‐reconstruction procedure was performed using a video‐assisted thoracoscopic surgical approach. In the remaining seven, the procedure was performed by conventional open thoracotomy. Results. Histomorphometric and biomechanical evaluation demonstrated that the video‐assisted thoracoscopic approach and open thoracotomy arthrodesis had comparable bone formation and biomechanical properties (P > 0.05). However, the Z‐plate fusions, as a group, demonstrated increased flexion‐extension stiffness properties and trabecular bone formation compared with the autograft and Bagby and Kuslich device fusions (P < 0.05). Conclusions. Thoracic interbody spinal fusions performed by thoracoscopy have demonstrated histologic, biomechanical, and radiographic equivalence to those performed by a thoracotomy approach. However, in the endoscopy group, intraoperative complications causing longer operative times, higher estimated blood loss, and increased animal morbidity indicated a substantial learning curve associated with the adoption of this surgical technique.

Cervical disc replacement in patients with and without previous adjacent level fusion surgery: A prospective study

Study Design. Prospective 6-center study. Objective. To evaluate outcomes of cervical disc replacement performed adjacent to a prior cervical fusion. Summary of Background Data. The use of disc replacement adjacent to a prior anterior cervical decompression and fusion (ACDF) is an attractive reconstructive option, obviating the need for a multilevel fusion. This study reports outcomes from patients with and without previous ACDF receiving the porous coated motion (PCM) artificial cervical disc in a United States Federal Drug Administration Investigational Device Exemption trials. Methods. Patients between ages of 18 and 65 with single-level cervical radiculopathy and/or myelopathy, unresponsive to at least 6 weeks of nonsurgical therapy, or experiencing progressive neurologic symptoms were enrolled. Clinical outcomes are compared for patients receiving a PCM disc at a level adjacent to a prior ACDF (“adjacent”) and those without having previously had fusion (“primary”). Results. 126 PCM patients were primary (mean age: 44.4 years.) and 26 patients had previous “adjacent level” fusion surgery (mean age: 46.4 years). Surgery time was similar in both groups (96 minutes and 98 minutes, respectively; P = 0.761), and mean blood loss was 76 mL and 66 mL in the 2 groups, respectively (P = 0.491). Clinical outcomes using Neck Disability Index and Visual Analog Scores neck and arm scores showed significant improvement after surgery and were similar between groups at all time points. Revision surgery occurred in 2 of 126 primary patients, and in 2 of 26 patients in the adjacent-to-fusion group. Conclusion. Although the level adjacent to a prior cervical fusion is subject to increased biomechanical forces, potentially leading to a higher risk of failure, the PCM disc was well tolerated in the short term. The early clinical results of disc replacement adjacent to a prior fusion are good and comparable to the outcomes after primary disc replacement surgery. However, in view of the small study population and short-term follow-up, continued study is mandatory.

The role of spinal instrumentation in augmenting lumbar posterolateral fusion.

Study Design Using a sheep model, clinically practical posterolateral intertransverse process fusion was successfully achieved and biomechanically tested to determine the load-sharing environment provided by spinal instrumentation and posterolateral fusion mass following solid arthrodesis. Objectives To quantify the in vivo load-sharing capacity of spinal instrumentation on augmenting the posterolateral intertransverse fusion. The hypothesis was that transpedicular screw fixation maintains the biomechanical contribution to the posterolateral fusion stability even after successful arthrodesis because of its providing anterior and middle column support. Summary of Background Data Although many previous studies have documented the biological and biomechanical advantages of posterolateral fusion, it is known that posterolateral fusion without spinal instrumentation allowed significant remaining motion at the fused segment even after the solid arthrodesis. Whether spinal instrumentation, especially transpedicular screw fixation, augments in vivo posterolateral fusion stability after solid arthrodesis has not been previously investigated. Methods Radiographic, macroscopic, and biomechanical analyses of a posterolateral intertransverse process fusion model were performed on 18 sheep at 4 months postoperatively. The load-sharing contribution of the spinal instrumentation was calculated based on the stability with or without spinal instrumentation tested in five loading modalities. Histomorphometry of the vertebral body spanned by spinal instrumentation provided the information regarding the biological effect of the load-sharing capacity of spinal instrumentation on bone remodelling. Results All sheep who received posterolateral intertransverse process fusion demonstrated successful solid arthrodesis and high biomechanical quality of the posterolateral fusion mass when compared to previous posterolateral fusion models. The significant difference in stiffness between fixation and subsequent fixation removal was observed in flexion, despite maintaining high lateral bending stiffness equivalent to the fixation (with instrumentation) level. This significant load-sharing contribution of spinal instrumentation detected in flexion corresponded to 27% when compared to the fixation level. The qualitative and quantitative bone histology showed 64% of the volumetric density of bone in the fixation group when compared to that of the sham group as well as narrow trabeculae and reduced connection of trabeculae. Conclusions The continuance in support offered by transpedicular screw fixation was assured in vivo after the solid posterolateral intertransverse process fusion. This was clearly demonstrated under eccentric loads in a sagittal plane, suggesting that transpedicular screw fixation was able to provide anterior and middle column support and resist eccentric loads.