250. Interspinous process distraction compared to nonoperative care for moderate lumbar degenerative disc disease: results of the FDA IDE clinical trial

Abstract

BACKGROUND CONTEXT Interspinous process distraction (IPD) devices aim to alleviate back and leg pain by limiting extension and unloading the 3-joint complex at the affected lumbar level. IPDs may offer a treatment option for painful degenerative disc disease (DDD) that is not yet indicated for fusion or disc replacement. PURPOSE To compare the safety and effectiveness of IPD and nonoperative treatment after 2 years for the treatment of moderate lumbar DDD. STUDY DESIGN/SETTING A prospective, randomized, controlled FDA IDE clinical trial at 23 US centers (ClinicalTrials.gov: NCT00456378). PATIENT SAMPLE A total of 278 patients with moderate low back pain for less than 1 year and radiographic evidence of single-level DDD between L2 and L5 who failed at least 6 weeks but less than 6 months of conservative management were randomized and treated with investigational IPD (n=181) or control nonoperative treatment (n=97). OUTCOME MEASURES The primary endpoint was Overall Success, a composite variable that included: 1) Oswestry Disability Index (ODI) score improvement of ≥ 15 points; and 2) no serious adverse event (AE) caused by the implant or by both the implant and surgical procedure (IPD) or caused by the nonoperative treatment (control); and 3) no secondary surgery (IPD) or treatment surgery (control) at the involved level. Additional safety and effectiveness endpoints included back and leg pain numerical (0-20) rating scales, SF-36 PCS/MCS, AEs and secondary surgeries. METHODS Investigational treatment consisted of the IPD implantation (without decompression) and nonoperative treatments, as necessary. Control treatment consisted of information/ education on low back pain, medication, physical therapy, and epidural and/or facet joint steroidal injections. Clinical and radiographic assessments were performed preoperatively, intra-operatively, and postoperatively up to 2 years. Statistical analyses used Bayesian methods with non-informative priors. Last observation was carried forward (LOCF) for patients lost to follow-up including patients receiving surgery (control crossovers) or additional surgery (IPD investigational) at the involved level. RESULTS Baseline demographic characteristics and outcomes scores were not statistically different between the two groups, except back pain (16.8 for investigational vs 16.1 for control, p=0.033). The IPD rate of Overall Success at 24-months was statistically superior to control (observed rate of 63.0% vs 13.4%, respectively; posterior probability of superiority (pps) > 99.9%). The improvement in outcomes for IPD was statistically superior to control (pps > 99.9%) for: ODI (26.4 vs 1.1), back pain (8.4 vs 1.2), leg pain (4.9 vs -1.1, PCS (12.6 vs.1.4), and MCS (4.4 vs -0.8). Spinous process bony erosion increased slowly to 33.7% (61/181) of patients but was not related to clinical outcomes. Treatment-related serious AEs in the control group were associated with increasing low back pain. Fifteen (8.3%) IPD and 34 (35.1%) control patients experienced a treatment-related serious AE. Twenty (11.0%) IPD patients had secondary surgery and 10 (10.3%) control patients had treatment surgery at the index level. After 6 months of nonoperative treatment, control patients had the option to crossover to IPD: 57 (58.8%) control patients had crossed over by 24 months. CONCLUSIONS These analyses support the superiority of this IPD over conservative care for moderate back pain in appropriately selected patients. FDA DEVICE/DRUG STATUS DIAM™ Spinal Stabilization System (Investigational/Not approved)