Faculty Bibliography

STUDY DESIGN: Biomechanical study of bovine spines. OBJECTIVE: The purpose of this study was to perform a biomechanical test to analyze intervertebral deflections following placement of both 1 and 2 semiconstrained TDRs in the subjacent segments of a long fusion. SUMMARY OF BACKGROUND DATA: Long-term sequela of long lumbar fusion for scoliosis include adjacent segment disease and flatback syndrome. Total disc replacement (TDR) is a viable option for the treatment of these conditions. Little data has been published regarding the placement of a TDR distal to a scoliosis fusion. METHODS: Six thoracolumbar bovine spines (T12-S1) were instrumented from T12 to L5, with bilateral pedicle screw fixation at each level. L5-L6 and L6-S1 served as the test levels. One TDR (FlexiCore, Stryker Spine, Allendale, NJ) was initially performed adjacent to the fusion, followed by a subsequent TDR insertion at the last spinal segment. The applied load, total specimen deflection, and local transducer deflections were recorded before and after a TDR at both levels. The results were expressed as a percentage of the intact specimen. Flexion, extension, lateral bending, and torsional deflections were recorded. RESULTS: There were no significant differences (P > 0.05) in sensor deflection observed at the L5-L6 and L6-S1 levels in the anterior and lateral transducers when compared to intact spines specimens. A similar effect was observed at the L5-L6 and L6-S1 levels in the anterior and lateral transducers when compared to intact or prior L5-L6 and intact L6-S1 constructs. CONCLUSION: This study has shown that using the FlexiCore system at 1 and/or 2 intervertebral disc spaces caudal to a scoliosis fusion model did not significantly change the sensor deflection at the 2 segments adjacent to a scoliosis fusion construct. Future research will continue to define the clinical setting and patients best suited for management by TDR systems

Background: Interlaminar-interspinous implants have gained acceptance as motion preservation devices. There are a limited number of posterior dynamic stabilization implants approved by the FDA. The purpose of this study was to review the long-term clinical outcomes of patients that had placement of an interspinous implant. Methods: This is a retrospective study of 124 patients that underwent placement of a interlaminar-interspinous implant (coflex, Paradigm Spine, New York, NY, U.S.A.) with a mean follow-up of 6.3 years. Patients were treated for spinal stenosis, spinal stenosis and lumbar disc herniation, or lumbar disc herniation. Preoperatively and postoperatively, patients were asked to grade their back and leg pain using the pain severity scale: no pain (0), mild pain (1), moderate pain (2), or severe pain (3). Patient satisfaction was queried concerning their operative procedure. Results: The mean severity of low back pain was decreased at the 2-year follow-up (moderate to mild, P < 0.001) and remained decreased with at least 5 years follow-up (moderate to mild, P < 0.001). The mean severity of leg pain was decreased at the 2-year follow-up (severe to mild, P < 0.001) and with at least 5 years follow-up (severe to mild, P < 0.001). Overall patient satisfaction demonstrated 7% were unsatisfied, 46% were satisfied, and 46% were very satisfied with the clinical outcome. Conclusion: This study has demonstrated that interlaminar-interspinous implant by coflex provides pain relief for patients with low back pain and leg pain. Interlaminar-inter-spinous implant by coflex is an option in the selection for dynamic stabilization

Objectives: Interlaminar-interspinous implants have gained acceptance as motion preservation devices. Currently, there are a limited number of posterior dynamic stabilization implants approved by the FDA. The purpose of this study was to perform a review of the long-term device related issues of an interlaminar-interspinous implant. Methods: This is a retrospective study of 99 patients who underwent placement of an interlaminar-interspinous implant (coflex, Paradigm Spine, New York, NY, U.S.A.) with a mean follow-up of 7 years. Patients were seen pre-operatively and postoperatively by one orthopaedic spine surgeon. Patients received radiographic analysis at follow-up visits, which was assessed by the operating surgeon for any device related issues. Results: All 99 patients received radiographs at their follow-up with the operating surgeon. The complications were catgorized into the following groups with their respective percentages: no device related issues (92%) and device related issues (8%). The patients with device related issues were categorized into the following groups: Broken U portion of implant (0%); Broken wing of the implant (1%); Displaced U portion of implant less than 5 mm (2%); Displaced U portion of implant more than 5 mm (2%); Displaced U portion of implant with unknown distance (1%); Removed implant (2%); Spinous process fracture (0%); bone-implant interface remodeling (0%). Conclusions: Displacement of the U portion of the implant was the most common complication and could be due to instability at the level of insertion. The data has demonstrated that in the short and long term follow-up, there are very few device related complications

BACKGROUND: The purpose of this study was to determine the indications for implantation of the coflex device (Paradigm Spine, LLC, New York, New York), assess long-term complications, and evaluate the long-term clinical outcomes of patients. METHODS: A total of 127 patients underwent placement of a coflex implant for various indications by one orthopaedic spine surgeon. The mean follow-up was 6.3 years. The original indications for implantation were determined based upon the data provided in the case report forms. Preoperatively and postoperatively, patients were asked to grade their low-back and leg pain using the visual analog scale (VAS) and the pain severity scale: no pain (0), mild pain (1), moderate pain (2), or severe pain (3). Patients were queried about their satisfaction with the surgical procedure. Follow-up radiographs were taken to determine any device-related issues. RESULTS: The most prevalent diagnoses for implantation were spinal stenosis (19.7%) and spinal stenosis with lumbar disc herniation (35.4%). The mean severity of low-back pain was decreased by 33% (from moderate to mild) at the 2-year follow-up (P < .001) and at the 5-year follow-up (from moderate to mild, P < .001). The mean severity of leg pain was decreased by 66% (from severe to mild) at the 2-year follow-up (P < .001) and at the 5-year follow-up (from severe to mild, P < .001). At the mean follow-up period of 6.3 years, a patient satisfaction query demonstrated that 7% were unsatisfied, 46% were satisfied, and 46% were very satisfied with their clinical outcome. Based on the follow-up radiographs, 92 of patients had no devicerelated issues and 8% had device-related issues. CONCLUSION: The data provided have demonstrated that the coflex implant provides pain relief for patients with low-back pain and leg pain. The most common indications for implantation were spinal stenosis and spinal stenosis with lumbar disc herniation. There were very few device-related complications. CLINICAL SIGNIFICANCE: Using coflex is a safe and viable option in the selection of instrumentation for spinal stabilization.

Introduction: The gold standard for the treatment of isthmic spondylolisthesis is posterior-lateral fusion. Few studies have evaluated the clinical outcomes of circumference fusion in the treatment if isthmic spondylolisthesis. The purpose of this study was to evaluate the surgical and clinical outcomes of anterior-posterior surgical treatment for low-grade isthmic spondylolisthesis. Methods: Retrospectively, 23 consecutive patients were enrolled that underwent surgical treatment for Isthmic Spondylolisthesis Grade 1 or 2. Basic demographic data was collected. Radiographic data that was collected included Meyerding Scale, disc height, and slip angle. Pre and post surgical clinical surveys which included VAS, ODI, and SF-36 surveys were collected. Results: There were 23 patients. All patients underwent anterior interbody fusion with a femoral ring allograft or iliac crest bone graft in addition to posterior lumbar decompression and fusion with instrumentation. The average slip percentage decreased from 23.2% to 19.0% (P = 0.24), slip angle increased from 9.8 to 17.9 (P < 0.001), and disc height decreased from 1.9 cm to 0.80 cm (P < .001). VAS scores decreased from 7.1 to 2.4 (P < 0.001). ODI scores decreased from 52.5 to 28.1 (P < 0.001). SF-36 scores demonstrated a significant increase in the Physical Component Scale (PCS) from 29.5 to 42.6 (P < 0.001). Conclusion: This study demonstrates that patients with isthmic spondylolisthesis that undergo circumferential fusion have a good clinical outcome. Patients demonstrated an improvement in the ODI and the physical component scores of the SF-36. These results demonstrate that patients improved in their physical functioning due to the surgery alone

STUDY DESIGN: Retrospective study of patients enrolled in prospective randomized Food and Drug Administration trial. OBJECTIVE: To evaluate the influence of pre- and postoperative disc height on postoperative motion and clinical outcomes. SUMMARY OF BACKGROUND DATA: Our understanding of the factors that influence motion and ultimately patient satisfaction after lumbar disc replacement continues to evolve. METHODS: Forty-two patients with a single level ProDisc-L at either the L4/5 or L5-S1 were selected. Pre- and postoperative disc height and range of motion (ROM) were measured from standing lateral and flexion-extension radiographs. Oswestry Disability Index and visual analog scale were also collected. Student t test and Spearman rho tests were performed to determine if there was any correlation or 'threshold' effect between the disc height and ROM or clinical outcome. RESULTS: The mean anterior and posterior disc height significantly increased from 10.8 mm to 17.6 mm and 4.4 mm to 7.9 mm, respectively (P < 0.01). The mean ROM decreased from 7.0 degrees to 5.7 degrees (P = 0.21). Patients with less than 9 mm of preoperative anterior disc height had an increase in their ROM (2.2 degrees) compared with a loss of ROM (-2.2 degrees) in patients with more than 9 mm of preoperative disc height (P = 0.02). Patients with between 16 mm and 18 mm of postoperative anterior disc height have greater ROM (7.5 degrees) than those above or below this range (3.6 degrees and 3.6 degrees respectively, P < 0.05). There was no correlation or threshold effect between clinical outcomes and disc height. CONCLUSION: Patients with greater disc collapse benefit more in ROM from a total disc replacement. The optimal range to maximize ROM for postoperative anterior disc height is 16 mm to 18 mm. This optimal range did not translate into better clinical outcome at 2 years follow-up

STUDY DESIGN: Retrospective outcome data analysis. OBJECTIVE: To evaluate if there is a significant difference between the midline rectus (MR) and the paramedian lateral rectus (PLR) approaches with regard to implant position for lumbar disc arthroplasty. To establish that a less than optimal implant position may influence clinical outcome. SUMMARY OF BACKGROUND DATA: Little is known about the impact of varying surgical approaches on lumbar artificial disc implant position and clinical outcome. METHODS: Fifty-seven patients were obtained from one center participating Food and Drug Administration study for the evaluation of the lumbar Prodisc-L. Two different surgical access techniques were compared; the MR and left PLR. Two independent evaluators calculated the postoperative radiographical displacement from the midline in the coronal and sagittal planes for each of the surgical techniques. Pre- and postoperative clinical outcomes were evaluated to determine which surgical access technique was associated with better outcomes and if there was a clinical correlation with technical accuracy. RESULTS: The PLR approach was associated with greater malalignment of the prosthesis in both the coronal and sagittal planes compared with the MR approach. However, the difference was significant only in the sagittal plane (P = 0.021). There was no significant difference in clinical outcome for either approach (P = 0.34). Patients with >or=5 mm prosthetic displacement from the midvertebral point had significantly worse Owestry disability index scores than patients with <3 mm malalignment in both the coronal and sagittal planes regardless of the surgical approach employed. CONCLUSION: The finding of a statistically significant more anteriorly displaced position in the sagittal plane of the total disc arthroplasty using the PLR approach may indicate a need to change to the MR approach. This study also demonstrates that patients with >or=5 mm prosthetic deviation from midline in either the coronal or sagittal planes had diminished clinical outcomes regardless of the approach used

STUDY DESIGN: This is a retrospective, independent study comparing 2 groups of patients treated surgically for discogenic low back pain associated with degenerative disc disease (DDD) in the lumbosacral spine. OBJECTIVE: To compare the surgical and hospitalization charges associated with 1- and 2-level lumbar total disc replacement and circumferential lumbar fusion. SUMMARY OF BACKGROUND DATA: Reported series of lumbar total disc replacement have been favorable. However, economic aspects of lumbar total disc replacement (TDR) have not been published or studied. This information is important considering the recent widespread utilization of new technologies. Recent studies have demonstrated comparable short-term clinical results between TDR and lumbar fusion recipients. Relative charges may be another important indicator of the most appropriate procedure. We report a hospital charge-analysis comparing ProDisc lumbar disc replacement with circumferential fusion for discogenic low back pain. METHODS: In a cohort of 53 prospectively selected patients with severe, disabling back pain and lumbar disc degeneration, 36 received Synthes ProDisc TDR and 17 underwent circumferential fusion for 1- and 2-level degenerative disc disease between L3 and S1. Randomization was performed using a 2-to-1 ratio of ProDisc recipients to control spinal fusion recipients. Charge comparisons, including operating room charges, inpatient hospital charges, and implant charges, were made from hospital records using inflation-corrected 2006 U.S. dollars. Operating room times, estimated blood loss, and length of stay were obtained from hospital records as well. Surgeon and anesthesiologist fees were, for the purposes of comparison, based on Medicare reimbursement rates. Statistical analysis was performed using a 2-tailed Student t test. RESULTS: For patients with 1-level disease, significant differences were noted between the TDR and fusion control group. The mean total charge for the TDR group was $35,592 versus $46,280 for the fusion group (P = 0.0018). Operating room charges were $12,000 and $18,950, respectively, for the TDR and fusion groups (P < 0.05). Implant charges averaged $13,990 for the fusion group, which is slightly higher than the $13,800 for the ProDisc (P = 0.9). Estimated blood loss averaged 794 mL in the fusion group versus 412 mL in the TDR group (P = 0.0058). Mean OR minutes averaged 344 minutes for the fusion group and 185 minutes for the TDR (P < 0.05) Mean length of stay was 4.78 days for fusion versus 4.32 days for TDR (P = 0.394). For patients with 2-level disease, charges were similar between the TDR and fusion groups. The mean total charge for the 2-level TDR group was $55,524 versus $56,823 for the fusion group (P = 0.55). Operating room charges were $15,340 and $20,560, respectively, for the TDR and fusion groups (P = 0.0003). Surgeon fees and anesthesiologist charges based on Medicare reimbursement rates were $5857 and $525 for the fusion group, respectively, versus $2826 and $331 for the TDR group (P < 0.05 for each). Implant charges were significantly lower for the fusion group (mean, $18,460) than those for 2-level Synthes ProDisc ($27,600) (P < 0.05). Operative time averaged 387 minutes for fusion versus 242 minutes for TDR (P < 0.0001). EBL and length of stay were similar. CONCLUSION: Patients undergoing 1- and 2-level ProDisc total disc replacement spent significantly less time in the OR and had less EBL than controls. Charges were significantly lower for TDR compared with circumferential fusions in the 1-level patient group, while charges were similar in the 2-level group