To determine if clinical outcomes are correlated with center of rotation (COR) in patients implanted with a viscoelastic total disc replacement (VTDR). Fifty patients with single-level, symptomatic lumbar DDD between L4 and S1 were enrolled in a clinical trial of a VTDR across three surgical centres. A comprehensive, independent review and statistical analysis of both clinical and radiographic outcomes was performed and analyzed for correlations. Data from preoperative through 2 years were available. The COR was calculated for the index levels and compared to data for an asymptomatic population. Each COR coordinate was classified as abnormal if outside of the 95% confidence interval for an asymptomatic population.Purpose
Methods
Surgical management of symptomatic lumbar degenerative disc disease (DDD) currently consists of fusion or implantation of a first generation total disc replacement (TDR). This study is the first to evaluate an elastomeric one-piece TDR in a 50-patient European study. Fifty patients with single-level, symptomatic lumbar DDD at L4-S1 who were unresponsive to at least 6-months of non-operative therapy were enrolled in a clinical trial of a viscoelastic TDR (VTDR) at three European sites. Patients were assessed clinically and radiographically at 6 weeks, 3 and 6 months, and 1 and 2 years. Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) were used to assess clinical outcomes. Twenty-eight males and twenty-two females were enrolled in the study. The average age of patients was 39.7 (23 to 61). The operative level was L4/L5 in 13 patients and L5/S1 in 37 patients. There were no intra-operative complications. Quantitative radiographic assessment indicates that the VTDR restores and maintains a physiologically appropriate disc height and angle, while providing range of motion and translation similar to those provided by the natural disc. Mean ODI scores decreased from 48% pre-operatively to 25% at two years follow up. Mean VAS low back pain scores decreased from 7.1 cm pre-op to 3 cm at two years. Median scores indicate that half of the patient population has ODI scores below 13% and VAS back pain scores below 0.5 cm. Clinically and radiologically, this elastomeric disc is performing satisfactorily, and the causes of clinical failures can be more readily identified.
