Faculty Bibliography

STUDY DESIGN: Retrospective study of patients enrolled in a prospective randomized Food and Drug Administration trial with single level cervical disc replacement (CDR) with the ProDisc-C (Synthes, Paoli, PA). OBJECTIVE: Evaluate the segmental range of motion (ROM) in the cervical spine pre- and postoperative after CDR. SUMMARY OF BACKGROUND INFORMATION: Each cervical level is believed to have its own biomechanical characteristics, ultimately leading to different sagittal and lateral ROM. Our understanding of the factors that influence motion after CDR continues to change and expand. METHODS: One hundred sixty-four patients with single level ProDisc-C arthroplasty were evaluated radiographically using Medical Metrics (QMATM, Medical Metrics, Inc., Houston, TX). Pre- and postoperative disc height and ROM were measured from standing lateral and flexion-extension radiographs. Of these 164 patients, 44 had a CDR at C6/C7, 96 at C5/C6, 18 at C4/C5, and 6 at C3/C4. The mean follow-up was of 24 months. Statistical analysis evaluated the difference in mean ROM between the groups. RESULTS: Before surgery, C4/C5 had more sagittal ROM compared with C3/C4, C5/C6, and C6/C7 (P < 0.001.) Before surgery, C4/C5 also had more lateral ROM compared with C3/C4, C5/C6, and C6/C7 (P = 0.015). After surgery, there were no significant differences in sagittal and lateral ROM between C3/C4, C4/C5, C5/C6, and C6/C7. The delta (difference between pre- and postoperative) proved that the C4/C5 CDR actually lost sagittal ROM (-2.5 degrees ) compared with the other levels, which gained sagittal ROM, C3/C4 (0.9 degrees ), C5/C6 (1.8 degrees ), and C6/C7 (1.6 degrees ); P = 0.037. There was no significant difference in the delta lateral ROM between the segments: C3/C4, C4/C5, C5/C6, and C6/C7. CONCLUSION: CDR approximates the different segmental sagittal and lateral ROM. Although C4/C5 had negative delta ROM in the sagittal and lateral planes, it provided a satisfactory final ROM. Long-term clinical outcome studies are needed to properly evaluate if these differences could ultimately affect the patients everyday life

BACKGROUND:Cervical total disk replacement (TDR) is intended to address pain and preserve motion between vertebral bodies in patients with symptomatic cervical disk disease. Two-year follow-up for the ProDisc-C (Synthes USA Products, LLC, West Chester, Pennsylvania) TDR clinical trial showed non-inferiority versus anterior cervical discectomy and fusion (ACDF), showing superiority in many clinical outcomes. We present the 4-year interim follow-up results. METHODS:Patients were randomized (1:1) to ProDisc-C (PDC-R) or ACDF. Patients were assessed preoperatively, and postoperatively at 6 weeks and 3, 6, 12, 18, 24, 36, and 48 months. After the randomized portion, continued access (CA) patients also underwent ProDisc-C implantation, with follow-up visits up to 24 months. Evaluations included Neck Disability Index (NDI), Visual Analog Scale (VAS) for pain/satisfaction, and radiographic and physical/neurologic examinations. RESULTS:Randomized patients (103 PDC-R and 106 ACDF) and 136 CA patients were treated at 13 sites. VAS pain and NDI score improvements from baseline were significant for all patients (P < .0001) but did not differ among groups. VAS satisfaction was higher at all time points for PDC-R versus ACDF patients (P = .0499 at 48 months). The percentage of patients who responded yes to surgery again was 85.6% at 24 months and 88.9% at 48 months in the PDC-R group, 80.9% at 24 months and 81.0% at 48 months in the ACDF group, and 86.3% at 24 months in the CA group. Five PDC-R patients (48 months) and no CA patients (24 months) had index-level bridging bone. By 48 months, approximately 4-fold more ACDF patients required secondary surgery (3 of 103 PDC-R patients [2.9%] vs 12 of 106 ACDF patients [11.3%], P = .0292). Of these, 6 ACDF patients (5.6%) required procedures at adjacent levels. Three CA patients required secondary procedures (24 months). CONCLUSIONS:Our 4-year data support that ProDisc-C TDR and ACDF are viable surgical options for symptomatic cervical disk disease. Although ACDF patients may be at higher risk for additional surgical intervention, patients in both groups show good clinical results at longer-term follow-up.

BACKGROUND CONTEXT: Anterior lumbar surgery is a common procedure for anterior lumbar interbody fusion and disc replacement but the impact of obesity on this procedure has not been determined. PURPOSE: To assess the perioperative outcomes of anterior retroperitoneal lumbar surgery in obese versus non-obese patients. STUDY DESIGN/SETTING: Prospective review of patients with anterior retroperitoneal lumbar disc procedures PATIENT SAMPLE: Seventy-four patients with anterior retroperitoneal lumbar disc procedures performed were evaluated. OUTCOME MEASURES: Access-related parameters included tissue depth (skin-to-fascia and fascia-to-spine depths), length of incision, estimated blood loss during the anterior procedure, the duration of the anterior exposure, and the duration of the entire anterior procedure. Outcome measures included complications attributable to the anterior procedure, analgesic use, length of time to ambulation, and length of hospitalization. METHODS: Seventy-four anterior retroperitoneal lumbar disc procedures were prospectively analyzed. Patient age, sex, body mass index, comorbidities, diagnosis, and operative parameters were collected. Access-related parameters and outcome measures were compared between obese and non-obese patients. Obesity was defined as body mass index greater than or equal to 30. RESULTS: There were 35 males and 39 females. Mean age was 46.6 years. The main diagnosis (63.5%) was discogenic back pain. Forty-one (55%) patients were non-obese and 33 were obese. The two patient groups were comparable in terms of age, sex, diagnosis, mean number of anterior levels operated, and previous abdominal surgery (all p>.05). In obese patients, there were two iliac vein lacerations (major complication rate, 6.1%), one superficial infection, and one urinary tract infection (minor complication rate, 6.1%). In non-obese patients, there were two iliac vein lacerations, one intestinal serosal tear (major complication rate, 7.3%), and two urinary tract infections (minor complication rate, 4.9%). There was no significant difference in the complication rates between obese and non-obese patients (p=.6). Obese patients have significantly longer duration of anterior exposure, duration of entire anterior surgery, longer length of anterior incision, and more depth from skin to fascia and from fascia to spine compared with non-obese patients. However, obesity does not affect blood loss, analgesic use, length of time to ambulation, and length of hospitalization. CONCLUSION: Perioperative outcomes in obese and non-obese patients were comparable and obesity is not related to an increased risk of morbidity in anterior lumbar surgery

BACKGROUND CONTEXT: Cervical total disc replacement (TDR) is an emerging technology. However, the factors that influence postoperative range of motion (ROM) and patient satisfaction are not fully understood. PURPOSE: To evaluate the influence of pre- and postoperative disc height on postoperative motion and clinical outcomes. STUDY DESIGN/SETTING: Retrospective review of patients enrolled in prospective randomized Food and Drug Administration (FDA) trial. PATIENT SAMPLE: One hundred sixty-six patients with single-level ProDisc-C arthroplasty performed were evaluated. OUTCOME MEASURES: ROM and clinical outcomes based on Neck Disability Index (NDI) and Visual Analog Scale (VAS) were assessed. METHODS: Preoperative and postoperative disc height and ROM were measured from lateral and flexion-extension radiographs. Student t test and Spearman's rho tests were performed to determine any correlation or 'threshold' effect between the disc height and ROM or clinical outcome. RESULTS: Patients with less than 4mm of preoperative disc height had a mean 1.8 degrees increase in flexion-extension ROM after TDR, whereas patients with greater than 4mm of preoperative disc height had no change (mean, 0 degrees ) in flexion-extension ROM (p=.04). Patients with greater than 5mm of postoperative disc height have significantly higher postoperative flexion-extension ROM (mean, 10.1 degrees ) than those with less than 5mm disc height (mean, 8.3 degrees , p=.014). However, patients with greater than 7mm of postoperative disc height have significantly lower postoperative lateral bending ROM (mean, 4.1 degrees ) than those with less than 7mm disc height (mean, 5.7 degrees , p=.04). It appears that the optimal postoperative disc height is between 5 and 7mm for increased ROM on flexion extension and lateral bending. There was a mean improvement of 30.5 points for NDI, 4.3 points for VAS neck pain score, and 3.9 points for VAS arm pain score (all p<.001). No correlation could be found between clinical outcomes and disc height. Similarly, no threshold effect could be found between any specific disc height and NDI or VAS. CONCLUSION: Patients with greater disc collapse of less than 4mm preoperative disc height benefit more in ROM after TDR. The optimal postoperative disc height range to maximize ROM is between 5 and 7mm. This optimal range did not translate into better clinical outcome at 2-year follow-up

BACKGROUND CONTEXT: Cervical total disc replacement (TDR) is intended to address radicular pain and preserve functional motion between two vertebral bodies in patients with symptomatic cervical disc disease (SCDD). PURPOSE: The purpose of this trial is to compare the safety and efficacy of cervical TDR, ProDisc-C (Synthes Spine Company, L.P., West Chester, PA), to anterior cervical discectomy and fusion (ACDF) surgery for the treatment of one-level SCDD between C3 and C7. STUDY DESIGN/SETTING: The study was conducted at 13 sites. A noninferiority design with a 1:1 randomization was used. PATIENT SAMPLE: Two hundred nine patients were randomized and treated (106 ACDF; 103 ProDisc-C). OUTCOME MEASURES: Visual analog scale (VAS) pain and intensity (neck and arm), VAS satisfaction, neck disability index (NDI), neurological exam, device success, adverse event occurrence, and short form-36 (SF-36) standardized questionnaires. METHODS: A prospective, randomized, controlled clinical trial was performed. Patients were enrolled and treated in accordance with the US Food and Drug Administration (FDA)-approved protocol. Patients were assessed pre- and postoperatively at six weeks, 3, 6, 12, 18, and 24 months. RESULTS: Demographics were similar between the two patient groups (ProDisc-C: 42.1+/-8.4 years, 44.7% males; Fusion: 43.5 +/- 7.1 years, 46.2% males). The most commonly treated level was C5-C6 (ProDisc-C: 56.3%; Fusion=57.5%). NDI and SF-36 scores were significantly less compared with presurgery scores at all follow-up visits for both the treatment groups (p<.0001). VAS neck pain intensity and frequency as well as VAS arm pain intensity and frequency were statistically lower at all follow-up timepoints compared with preoperative levels (p<.0001) but were not different between treatments. Neurologic success (improvement or maintenance) was achieved at 24 months in 90.9% of ProDisc-C and 88.0% of Fusion patients (p=.638). Results show that at 24 months postoperatively, 84.4% of ProDisc-C patients achieved a more than or equal to 4 degrees of motion or maintained motion relative to preoperative baseline at the operated level. There was a statistically significant difference in the number of secondary surgeries with 8.5% of Fusion patients needing a re-operation, revision, or supplemental fixation within the 24 month postoperative period compared with 1.8% of ProDisc-C patients (p=.033). At 24 months, there was a statistically significant difference in medication usage with 89.9% of ProDisc-C patients not on strong narcotics or muscle relaxants, compared with 81.5% of Fusion patients. CONCLUSIONS: The results of this clinical trial demonstrate that ProDisc-C is a safe and effective surgical treatment for patients with disabling cervical radiculopathy because of single-level disease. By all primary and secondary measures evaluated, clinical outcomes after ProDisc-C implantation were either equivalent or superior to those same clinical outcomes after Fusion

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