Abstract
Background:
Disc replacement arthroplasty previously has been shown to be an effective alternative to spine fusion for the treatment of single-level lumbar degenerative disc disease. The purpose of the present study was to determine the twenty-four-month results of a clinical trial of the ProDisc-L total disc replacement as compared with spinal fusion for the treatment of degenerative disc disease at two contiguous vertebral levels from L3 to S1.
Methods:
A total of 237 patients were treated in a randomized controlled trial designed as a non-inferiority study for regulatory application purposes. Blocked randomization was performed with use of a 2:1 ratio of total disc arthroplasty to circumferential arthrodesis. Evaluations, including patient self-assessments, physical and neurological examinations, and radiographic examinations, were performed preoperatively, six weeks postoperatively, and three, six, twelve, eighteen, and twenty-four months postoperatively.
Results:
At twenty-four months, 58.8% (eighty-seven) of 148 patients in the total disc replacement group were classified as a statistical success, compared with 47.8% (thirty-two) of sixty-seven patients in the arthrodesis group; non-inferiority was demonstrated. The mean Oswestry Disability Index in both groups significantly improved from baseline (p < 0.0001); the mean percentage improvement for the total disc replacement group was significantly better than that for the arthrodesis group (p = 0.0282). An established clinical criterion for success, a =15-point improvement in the Oswestry Disability Index from baseline, occurred in 73.2% (109) of 149 patients in the total disc replacement group and 59.7% (thirty-seven) of sixty-two patients in the arthrodesis group. The Short Form-36 physical component scores were significantly better for the total disc replacement group as compared with the arthrodesis group (p = 0.0141 at twenty-four months). Visual analog scale scores for satisfaction significantly favored total disc replacement from three to twenty-four months. At twenty-four months, 78.2% (111) of 142 patients in the total disc replacement group and 62.1% (thirty-six) of fifty-eight patients in the arthrodesis group responded "yes" when asked if they would have the same surgery again. Lumbar spine range of motion on radiographs averaged 7.8° at the superior disc and 6.2° at the inferior disc in patients with total disc replacement. Reduction in narcotics usage significantly favored the total disc replacement group at twenty-four months after surgery (p = 0.0020).
Conclusions:
Despite the relatively short duration of follow-up and design limitations, the present study suggests that two-level lumbar disc arthroplasty is an alternative to and offers clinical advantages in terms of pain relief and functional recovery in comparison with arthrodesis. Longer-term follow-up is needed to determine the risks for implant wear and/or degenerative segment changes.
Level of Evidence:
Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.
Lumbar total disc arthroplasty previously has been shown to be an effective alternative to lumbar arthrodesis for the treatment of symptomatic degenerative disc disease at a single level in patients undergoing surgical treatment1,2. The purpose of the present study was to evaluate lumbar disc arthroplasty as an alternative to lumbar arthrodesis for the treatment of degenerative disc disease at two adjacent levels.
Arthrodesis has been utilized for the treatment of lumbar degenerative disc disease in patients who have had unsuccessful nonoperative care such as medication, physical therapy, or chiropractic treatment1-7. Arthrodesis alters the biomechanics of the spine as motion is lost at the fused level (or levels), and the overall sagittal alignment may shift. These changes in biomechanics generally become more pronounced as the number of fused vertebral levels increases and may exert excessive forces at adjacent vertebral levels8-13.
Total disc arthroplasty has been developed and used clinically to maintain motion and to reduce the biomechanical changes associated with arthrodesis. Previous randomized clinical trials of lumbar disc arthroplasty treatment at a single level demonstrated results that were equivalent or superior to those of lumbar interbody arthrodesis at two years of follow-up1,2. Longer-term follow-up of these trials has shown that these outcomes have been maintained14,15.
Although two-level lumbar total disc arthroplasty has been described in the literature, to our knowledge, there have been no randomized studies comparing lumbar arthrodesis with arthroplasty16-18. The purpose of the current report is to present the twenty-four-month results of a prospective, randomized, controlled, multicenter clinical trial comparing lumbar total disc arthroplasty with arthrodesis for the treatment of two-level degenerative disc disease. The hypothesis of the study was that patients in the arthroplasty group would achieve at least the same level of clinical improvement as those in the arthrodesis group.
Study Design
Patients who had had at least six months of unsuccessful nonoperative care for the treatment of two-level lumbar degenerative disc disease were enrolled in a multicenter, prospective, randomized, controlled clinical trial, which was registered with ClinicalTrials.gov (NCT00295009). The trial was performed under an investigational device exemption (IDE) protocol to evaluate the safety and effectiveness of the ProDisc-L (Synthes USA, West Chester, Pennsylvania) total disc replacement at two adjacent lumbar levels for the purpose of a Food and Drug Administration (FDA) application. The trial was designed as a non-inferiority study. A composite end point was used to compare ProDisc-L total disc replacement with arthrodesis.
Study Population
All patients in the study had degenerative disc disease at two contiguous vertebral levels from L3 to S1 with or without leg pain, had had a minimum of six months of unsuccessful nonoperative treatment, and had a minimum Oswestry Disability Index (ODI) score of =40. Degenerative disc disease was defined as lumbar spine instability, loss of intervertebral disc height, scarring of the anulus fibrosus, herniated nucleus pulposus, or vacuum phenomenon of the disc. Flexion-extension radiographs, computed tomography (CT), magnetic resonance imaging (MRI), discography, and/or myelography were used to confirm diseased disc levels. Major exclusion criteria included spondylolisthesis classified as greater than grade I, degenerative disc disease at more than two levels, previous arthrodesis, and inability to comply with the study protocol.
Study approval was obtained from each site's institutional review board prior to the start of the study. Patient randomization was performed with use of a 2:1 ratio of total disc arthroplasty to circumferential arthrodesis. Separate blocked randomization schedules were generated for each site with use of a fixed block size of six. The randomization was held by the sponsor and was disclosed to the site only after individual patient enrollment, with signed written informed consent provided by the patient. Patients were blinded to the treatment assignment prior to surgery. Patients in the investigational group were managed with total disc replacement at both levels. The control group was managed with a two-level anterior lumbar interbody arthrodesis with use of a commercially available femoral ring allograft and posterolateral arthrodesis with autogenous iliac crest bone graft in combination with pedicle screw instrumentation.
Device Description and Surgical Technique for ProDisc-L
The ProDisc-L total disc replacement is a semi-constrained design based on the ball-and-socket principle19-21. The prosthesis consists of two end plates manufactured from cobalt-chromium-molybdenum (CoCrMo) alloy and a convex ultra-high molecular weight polyethylene (UHMWPE) insert. Fixation is provided by a central keel and titanium plasma spray coating on each end plate.
The surgical technique of performing the two-level lumbar arthroplasty is similar to that of a single-level lumbar arthroplasty, which was previously described by Zigler et al.1.
Clinical Outcome Measurements
Each patient was clinically evaluated preoperatively, at six weeks postoperatively, and at three, six, twelve, eighteen, and twenty-four months postoperatively. Every visit included physical and neurological examinations, radiographic evaluation, determination of medication use, work and recreation status, and completion of self-assessment questionnaires (including the ODI, Short Form of the Medical Outcomes Study [SF-36], and visual analog scales [VAS] for pain and satisfaction). Physical and neurological examinations were performed to assess nerve root tension, reflexes, muscle strength, and sensory deficits. Radiographic evaluation consisted of neutral anteroposterior and lateral views, flexion-extension views, and lateral bending views. A qualitative and quantitative analysis of each radiograph was performed by independent radiologists at Medical Metrics (Houston, Texas).
Statistical Methods
The sample size was computed with use of an exact version of the original approximate calculation of Blackwelder22. Based on the choice of a type-I error of 5% (one-sided) and 80% power and the assumption of an 85% chance of statistical success at twenty-four months in each group, the sample size was 170 in the total disc replacement group and eighty-five in the arthrodesis group, for a total of 255 patients, with correction for 15% attrition.
For the purposes of FDA evaluation, a composite, binary end point consisting of ten criteria was established for each treatment group (Table I). At twenty-four months of follow-up, each patient was classified as either a statistical success or failure. In order to be classified as a statistical success, a patient had to meet all ten criteria; a patient who failed to meet one or more of the criteria was classified as a statistical failure. To determine study success, the percentage of patients who were classified as a statistical success was tabulated for the total disc replacement and arthrodesis groups. The test of the sole, primary non-inferiority hypothesis—that the treatment with total disc arthroplasty would be non-inferior to arthrodesis at twenty-four months—was based on an exact 95% one-sided, upper confidence bound for the difference in overall statistical success probabilities between the two groups. If the upper bound was =12.5%, then arthroplasty would be considered non-inferior to arthrodesis.
For demographic, secondary, and exploratory analyses, the Wilcoxon rank-sum test was performed for comparisons of continuous data between the treatment groups. The Fisher exact test was performed for comparisons of categorical data. Within-treatment-group comparisons of data at follow-up time points relative to baseline were assessed with use of the paired t test.
Source of Funding
Synthes USA Products, LLC, funded the randomized clinical trial (RCT) presented in this paper. Funds were used to support study-related expenses of the investigational sites, enrolled patients, and surgeon investigators.
From January 2002 to June 2004, a total of 256 patients were randomized by thirty-eight spine surgeons at sixteen sites across the United States. Nineteen patients were enrolled but were not treated: eight patients voluntarily withdrew, three were withdrawn by the treating surgeon, three no longer met the inclusion-exclusion criteria at time of surgery, and five did not have insurance coverage. Overall, 237 patients (165 in the total disc replacement group and seventy-two in the arthrodesis group) were treated. During the course of the study, one death occurred (unrelated to treatment), ten secondary surgical procedures were done, and fifteen patients were lost to follow-up. Of the 211 patients who were evaluated at the time of the twenty-four-month follow-up, eight had incomplete data; specifically, six had missing radiographs, two had missing neurological data, and one had missing SF-36 scores. For the purpose of evaluating the composite end point (study success or failure), data from 215 patients could be used (148 in the total disc replacement group and sixty-seven in the arthrodesis group). A total of 203 patients (including 143 in the total disc replacement group and sixty in the arthrodesis group) had complete data sets at twenty-four months (Fig. 1).
Flow diagram of the study design.
Overall, preoperative demographic data showed no significant differences between the treatment groups in terms of sex, age, body-mass index (BMI), or smoking status. The majority of patients (including 148 [89.7%] of 165 in the total disc replacement group and sixty-eight [94.4%] of seventy-two in the arthrodesis group) had back pain, with or without leg pain, that had lasted for more than one year. All patients had had at least six months of unsuccessful nonoperative treatment. The groups were similar in terms of previous unsuccessful operative and nonoperative treatment (Table II).
Intraoperative data showed that the total disc replacement group had significantly decreased operative times (p < 0.0001), estimated blood loss (p = 0.0013), and length of hospital stay (p < 0.0001) (Table III). Postoperative discharge was determined by the patient's ability to transfer and walk independently.
Clinical Outcomes: Primary
Composite End Point
As described in the Materials and Methods section, a composite regulatory FDA-guided end point consisting of ten criteria was tabulated for each treatment group. At twenty-four months, eighty-seven (58.8%) of 148 patients in the total disc replacement group and thirty-two (47.8%) of sixty-seven patients in the arthrodesis group met all ten criteria and were considered a study success; non-inferiority was demonstrated between the two groups with use of a Blackwelder hypothesis with ? = 0.125 (p = 0.0008). The difference between the two treatments was not significant (p = 0.0874). Individual clinical outcomes measurements are detailed in the following sections.
Oswestry Disability Index (ODI)
The ODI low back pain disability questionnaire is a validated method of assessing a patient's level of pain and functional disability. Baseline preoperative ODI values were similar for both treatment groups (64.7 points for the total disc replacement group, compared with 64.8 points for the arthrodesis group) (Table IV). In both groups, patients showed significant improvement in ODI scores from baseline at all follow-up periods (p < 0.0001). The total disc replacement group demonstrated significantly greater improvement than the arthrodesis group did at all follow-up time points (p = 0.0474). At twenty-four months, the mean improvement from baseline was 52.4% in the total disc replacement group compared with 40.9% in the arthrodesis group (p = 0.0282).
SF-36 Physical Component Score
Baseline preoperative values for the SF-36 physical component score (PCS) were similar for both treatment groups (29.5 points for the total disc replacement group, compared with 30.1 points for the arthrodesis group) (Table V). Both treatment groups showed significant improvement at all follow-up time-points in comparison with baseline (p < 0.0279). The total disc replacement group showed significant improvement compared with the arthrodesis group at six weeks and at three, six, and twenty-four months (p = 0.0379, p = 0.0044, p = 0.0068, and p = 0.0141, respectively). At twenty-four months, the score for the total disc replacement group improved to a mean of 43.9 points and the score for the arthrodesis group improved to a mean of 39.2 points.
Neurological Success
Neurological success was defined as the maintenance or improvement of patient responses to all neurological criteria, including motor status, sensory status, reflexes, and a straight leg raise test (Table VI). At six months, the percentage of patients with neurological success was significantly higher in the total disc replacement group (87.3%; 131 of 150) than in the arthrodesis group (71.6%; forty-eight of sixty-seven) (p = 0.0068). At twenty-four months, the percentage remained higher in the total disc replacement group (89.2%; 132 of 148) than in the arthrodesis group (80.6%, fifty of sixty-two), but this small difference was not significant.
Secondary Surgical Procedures
Overall, four (2.4%) of 165 patients in the total disc replacement group and six (8.3%) of seventy-two patients in the arthrodesis group required a secondary surgical procedure at the index level or levels. This fourfold difference in the rate of secondary surgery for the arthrodesis group was significant (p = 0.0465). The average number of days from the index procedure to secondary surgery was 567.7 (range, 480 to 736) in the total disc replacement group and 255.5 (range, twenty-one to 560) in the arthrodesis group. One patient (0.6%) in the total disc replacement group had anterior migration of the superior arthroplasty implant and underwent revision arthrodesis at that level. The remaining three patients (1.8%) in the total disc replacement group underwent a secondary surgical procedure (foraminotomy and/or facetectomy) for posterior decompression; two of these patients underwent a one-level decompression, and one patient underwent a decompression at both levels. Of the six patients who underwent a secondary surgical procedure in the arthrodesis group, five had spinal implant removal because of ongoing pain and one had implant removal, decompression (bilateral medial facetectomy and hemilaminectomy), and revision of the bone fusion sites because of a pseudarthrosis at L5-S1.
Radiographic Outcomes
The radiographic outcomes that were assessed included device migration, device subsidence, disc height, radiolucency around the implant, and flexion-extension range of motion in the total disc replacement group and fusion status in the arthrodesis group. With the exception of the patient who experienced anterior migration of the superior arthroplasty implant, there were no reported instances of device migration, radiolucency, or >3-mm loss of disc height in the total disc replacement group. Three patients (2.1%) in the total disc replacement group had device subsidence of >3mm, but this finding was not considered to be clinically important in any of these patients. At twenty-four months, the flexion-extension lumbar range of motion in the total disc replacement group averaged 7.8° ± 5.3° at the level of the superior disc and 6.2° ± 4.1° at the level of the inferior disc (Fig. 2).
Lateral radiographs of the lumbar spine of a thirty-eight-year-old man, made twenty-four months after treatment with the ProDisc-L total disc replacement at L3-L4 and L4-L5. The radiographs were made in neutral (left), flexion, (middle), and extension (right). The Oswestry Disability Index was 62 preoperatively and 26 at twenty-four months, representing an improvement of 36 points (58%). The visual analog scale pain score was 68.0 preoperatively and 13.1 at twenty-four months, representing an improvement of 54.9 points (80.7%). The patient answered "yes" to the question of whether he would undergo the procedure again. The range of motion was 9.3° (cranial) and 13.0° (caudal) preoperatively and 12.7° (cranial) and 15.7° (caudal) at twenty-four months.
Radiographic success in the arthrodesis group required evidence of fusion with >50% bridging trabecular bone or bone mass maturation between the adjacent end plates and no visible gaps in the fusion mass (77.0%, forty-seven of sixty-one patients); no halos or radiolucencies around the implant (95.1%, fifty-eight of sixty-one patients); no evidence of device migration or of subsidence of >3 mm (98.4%, sixty of sixty-one patients); no loss of disc height of >3 mm (100%, sixty-one of sixty-one patients); and no motion (<10° of total angulation for two levels combined) on flexion-extension radiographs (100%, sixty-one of sixty-one patients). One patient was clinically symptomatic and required revision surgery because of pseudarthrosis at the arthrodesis site.
Clinical Outcomes: Secondary
Visual Analog Scale for Pain
For both groups, the VAS pain assessment showed significant improvement from preoperative levels at all time points postoperatively (p < 0.0001) (Table VII). At twenty-four months, the mean VAS score demonstrated a 43.3-mm mean reduction from baseline for the total disc replacement group compared with a 36.7-mm mean reduction for the arthrodesis group. A significant difference between the treatment groups was observed only at the eighteen-month follow-up (p = 0.0248).
Visual Analog Scale for Patient Satisfaction and Willingness to Undergo Surgery Again
Patients indicated their level of satisfaction with treatment by placing a mark on a printed 100-mm scale, with 100 mm indicating that the patient was completely satisfied. The resulting score was the ratio of the patient response to the total length of the scale. The VAS score for patient satisfaction showed a significant difference in favor of the total disc replacement group at all follow-up time points except six weeks (Table VIII). At twenty-four months, the mean score was 77.7 mm for the total disc replacement group compared with 68.9 mm for the arthrodesis group (p = 0.0126).
Patients were asked whether they would have the same surgical treatment again. At six weeks through eighteen months, patients responded "yes" at a significantly higher rate in the total disc replacement group than in the arthrodesis group (p < 0.0384). At twenty-four months, the percentage of patients who responded "yes" was 78.2% (111 of 142) in the total disc replacement group compared with 62.1% (thirty-six of fifty-eight) in the arthrodesis group (p = 0.0546).
Narcotic Use
Preoperatively, 69.1% (114) of 165 patients in the total disc replacement group and 63.9% (forty-six) of seventy-two patients in the arthrodesis group reported using narcotics. At twenty-four months, there was a significant decrease, favoring the total disc replacement group, in terms of the percentage of patients using narcotics (p = 0.0020). At that time, only 36.1% (fifty-two) of 144 patients in the total disc replacement group were using narcotics, representing a 47.8% decrease, whereas 59.3% (thirty-five) of fifty-nine patients in the arthrodesis group were using narcotics, representing a 7.2% decrease (Fig. 3).
Line graph showing the percentage of patients using narcotics for each surgical treatment over time. TDR = total disc replacement.
Work and Recreation Status
Preoperatively, there was no significant difference between the total disc replacement group (79.4%; 131 of 165) and the arthrodesis group (83.3%; sixty of seventy-two) in terms of the employment rate (p = 0.5928). Similarly, at twenty-four months, there was no significant difference between the total disc replacement group (80.4%; 115 of 143) and the arthrodesis group (86.0%; forty-nine of fifty-seven) in terms of the employment rate (p = 0.4193).
Preoperatively, there was no significant difference between the total disc replacement group (36.4%; sixty of 165) and the arthrodesis group (43.7%; thirty-one of seventy-one) in terms of the percentage of patients participating in recreational activities (p = 0.3099). The percentage of patients participating in recreational activities had increased in both groups at twenty-four months, with no significant difference between the total disc replacement group (84.6%; 121 of 143) and the arthrodesis group (79.7%; forty-seven of fifty-nine) (p = 0.4121).
Complications
Major surgery-related complications included one dural tear in the total disc replacement group (prevalence, 0.6%; one of 165) and three dural tears in the arthrodesis group (prevalence, 4.2%; three of seventy-two). The one dural tear in the total disc replacement group occurred during preparation of the disc space as a bridging osteophyte and calcified disc limited the opening of the posterior disc space. The three durotomies in the arthrodesis group occurred during decompressive hemilaminotomies. All four dural rents were successfully repaired. Blood loss of >1500 mL occurred in two (1.2%) of 165 patients in the total disc replacement group and two (2.8%) of seventy-two patients in the arthrodesis group. One of the two patients in the total disc replacement group sustained an iliac artery tear, whereas the other patient in the total disc replacement group and the two patients in the arthrodesis group had excessive oozing from the decompression, decorticated bone, and graft sites. Postoperatively, deep venous thrombosis was reported in two (1.2%) of 165 patients in the total disc replacement group and two (2.8%) of seventy-two in the arthrodesis group; all thromboses were successfully treated.
Randomized controlled trials have demonstrated that lumbar total disc arthroplasty is an effective alternative to lumbar arthrodesis for the treatment of degenerative disc disease at a single vertebral level in patients who have had unsuccessful nonoperative care1,2. To our knowledge, the present study is the first randomized controlled trial to compare disc arthroplasty with arthrodesis for the treatment of two-level degenerative disc disease. Despite having had six months of unsuccessful nonoperative care prior to entering this study, both groups demonstrated substantial improvement at twenty-four months after surgery in comparison with the preoperative status. Statistical non-inferiority of arthroplasty compared with arthrodesis was established for the composite regulatory end point. These results suggest that the ProDisc-L total disc replacement is an appropriate alternate treatment to lumbar arthrodesis in this patient population.
Multicenter, prospective, randomized, controlled clinical trials provide the best level of evidence for evaluating medical devices. Although the present study suggests that arthroplasty is an effective alternative to arthrodesis and may provide statistically better outcomes, these interpretations should be kept in perspective. The statistical composite end point in the present study was designed exclusively for regulatory application purposes and is not a clinically relevant representation of patient outcomes. A patient in the total disc arthroplasty group with complete neurological resolution, 90% improvement in terms of the Oswestry Disability Index (ODI), a high level of satisfaction, and no use of medications to control pain would have been classified as a composite end point failure in this study if he or she failed to demonstrate adequate motion at the twenty-four-month follow-up visit. In clinical practice, the outcome for this patient would be considered to be good. Each investigational device exemption trial has a unique composite end point, making comparisons between studies difficult.
The clinical relevance of the effect of treatment was revealed in multiple patient outcomes. Prior to treatment, despite having received at least six months of nonoperative care, patients who were enrolled in this randomized controlled trial continued to have debilitating back pain (mean ODI score, 65; reported narcotics usage, 67.5% [160 of 237]). Postoperatively, an improvement in ODI scores and a reduction in narcotics usage were seen in both study groups. A 15-point improvement in the ODI score from baseline, an established criterion for the evaluation of the clinical success of the outcomes of lumbar spine surgery23-25, was seen in 68.5% (146) of 213 patients in the study, with a significantly higher percentage of patients in the total disc replacement group showing at least a 15-point improvement in the ODI score at the time of the twenty-four-month follow-up (73.2% [109 of 149] in the total disc replacement group, compared with 59.7% [thirty-seven of sixty-two] in the arthrodesis group) (p = 0.0398). Of the patients who achieved at least a 15-point improvement in the ODI score at twenty-four months, only 19.3% (twenty-one) of 109 patients in the total disc replacement group continued to use narcotics in contrast to 40.5% (fifteen) of thirty-seven patients in the arthrodesis group (p = 0.0145). Patients in the total disc replacement group improved more rapidly than did those in the arthrodesis group, as indicated by their significant rates of improvement in terms of the ODI and Short Form-36 physical component scores (SF-36 PCS) at early follow-up visits at six weeks and three and six months. The visual analog scale scores for satisfaction and the percentage of patients who stated that they would have the surgery again confirmed the clinical findings: patients were satisfied with the outcomes following surgery and would choose to have surgery again. These clinical results suggest that patients who are managed with arthroplasty demonstrate a higher level of improvement in terms of pain and function at twenty-four months as compared with patients who are managed with arthrodesis.
Despite the positive findings, the present study was limited by its regulatory design. It was not practical to keep patients blinded postoperatively with regard to the treatment received because of the use of radiographic evaluation and the posterior incision required by posterolateral arthrodesis. This feature had the potential for patient bias in favor of the arthroplasty treatment, especially at earlier time points. It has been proposed that, by twenty-four months after surgery, most of this treatment bias would have diminished26. The twenty-four-month end point of this study was not long enough to adequately evaluate the benefits or disadvantages of arthroplasty or arthrodesis. Over the long term, total disc arthroplasty is associated with a risk of implant polyethylene wear or further degenerative changes.
It has been hypothesized that changes in spinal biomechanics as a result of arthrodesis may contribute to or accelerate adjacent-level disc disease. If arthroplasty offers any meaningful benefits over arthrodesis in terms of adjacent-level disc degeneration, this would not be detectable until longer-term follow-up. At the time of the development of the present study, total disc arthroplasty was in its infancy. It was thought that maintaining or increasing lumbar flexion-extension range of motion would correlate with improved clinical outcomes. We are aware of no study that has shown such a correlation. Other important factors beyond the absolute range of motion, such as the quality of motion, sagittal balance, and spinal alignment, may influence the effect of arthroplasty. Although all patients who were enrolled in this study received characteristic nonoperative care for a minimum of six months, the type of therapy was not specified by the study protocol.
The present study supports the use of two-level lumbar total disc arthroplasty as a viable alternative to lumbar arthrodesis for the treatment of two-level degenerative disc disease. Our preliminary conclusion, based on our relatively short twenty-four-month follow-up, is that the ProDisc-L total disc replacement offers advantages over arthrodesis in terms of pain relief and functional recovery.
Note: The authors thank the co-investigators of the two-level ProDisc-L IDE study, Johanna Hantel, BA, Synthes USA Products, LLC, for her editorial collaboration, and Jeff Stein, PhD, and Peter Yao, MS, Synthes USA Products, LLC, for their assistance with the statistical analysis.
The primary surgeon investigators of the two-level ProDisc-L IDE study included Rick Delamarter, MD; Jack E. Zigler, MD; Richard A. Balderston, MD; Jeffrey M. Spivak, MD; Raymond J. Linovitz, MD; James F. Zucherman, MD; James J. Yue, MD; Thomas T. Haider, MD; Scott H. Kitchel, MD; Frank P. Cammisa, MD; Guy O. Danielson III, MD; Doug Geiger, MD; Robert Watkins, MD; Hansen Yuan, MD; John E. Sherman, MD; Harry N. Herkowitz, MD; Michael A. Kropf, MD; and Jeffrey A. Goldstein, MD.
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FDA. FDA Center for Devices and Radiological Health, Orthopedics and Rehabilitation Devices Panel Meeting, .