91. The viable disc tissue allograft supplementation (VAST) randomized controlled trial in patients with chronic discogenic low back pain: Correlating age with clinical outcome

BACKGROUND CONTEXT The development of chronic low back pain (LBP) results from internal disc disruption within the nucleus pulposus and is the most common etiology of LBP in young to middle-age adults. A viable disc tissue allograft has been developed to supplement tissue loss associated with degenerative lumbar disc disease and the development of chronic discogenic LBP. PURPOSE In this study, the clinical outcomes of patients in the VAST study were analyzed on the basis of patient age (above and below the median age of all patients). STUDY DESIGN/SETTING Randomized, controlled, multicenter study in US. PATIENT SAMPLE A total of 218 patients with chronic low back pain secondary to single-level or two-level degenerative disc disease were enrolled in the study. Patients had back pain for a minimum of 6 months that was recalcitrant to nonoperative treatment modalities. Inclusion criteria also included pretreatment VASPI ≥ 40 and ODI Score ≥ 40. OUTCOME MEASURES Oswestry Disability Index (ODI) and visual analog scale of pain intensity (VASPI), neurological exam and adverse events. Plain film radiographs and magnetic resonance (MR) imaging scans were used to assess disc space height and spinal alignment and to determine the degree of disc degeneration. METHODS Prospective, multicentered, blinded, randomized clinical trial for subjects with single or two-level degenerative lumbar disc disease was conducted. Patients had back pain for a minimum of 6 months, which was recalcitrant to nonoperative treatment modalities. Patients were blinded and randomized to receive intradiscal injections of either viable disc allograft or saline, or to continue nonblinded with nonsurgical management (NSM). The NSM group could cross over to the allograft group after 3 months. All patients crossed over into the investigational allograft treatment group. Patient data based on age comparing younger patients (19-42 years, 104 patients) to older patients (43-73 years, 114 patients) across all three groups were analyzed. Statistical analyses were performed based on 12-month post treatment improvements in ODI and VAS. RESULTS In the younger patient group, a significantly larger improvement in ODI of 29.7 points in the allograft treated group and 45.0 points in the cross over group was observed vs 17.4 points with the saline group (Overall p-value =.004). This effect was also observed in multiple responder analyses with a significantly higher percentage of allograft-treated patients demonstrating ≥15 and ≥20-point improvements in ODI vs the saline group. 69.1% of the younger patients treated with viable allograft vs 35.3% of the saline group showed clinically meaningful improvement of ODI ≥20-points (Overall p-value=.004). No significant interaction between treatment and age in VAS, and no significant benefits of allograft treatment on VAS in younger vs older patients was observed. Adverse events were reported in 30.9%, 10.5% and 17.6% of younger patients in the allograft, placebo, and conservative care groups, respectively (overall p value=0.155), compared to 28.8%, 15.8%, and 9.1% of older patients in these groups (overall p value=0.136), most commonly back pain. CONCLUSIONS This subgroup analysis indicates that younger patients (≤ 42 years) have more favorable clinical outcome vs older patients at 12 months. This data suggests that a viable disc tissue injection can effectively treat chronic discogenic LBP nonsurgically with meaningful results demonstrated in a younger patient population. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.