Correlation between range of motion and outcome after lumbar total disc replacement: 8.6-year follow-up

Study Design. Retrospective radiographic and chart review. Objective. To examine the relationship between lumbar total disc replacement (TDR) range of motion (ROM) and clinical outcome at 8.6-year follow-up. Summary of Background Data. There are no studies on the relationship between TDR motion and clinical outcomes. Methods. We reviewed 38 patients who underwent 1 or 2-level TDR implantation with 51 TDR. Flexion-extension ROM was measured on lateral radiographs. Clinical outcomes were measured at 8.6 years by modified Stauffer-Coventry scores, Oswestry Disability Questionnaires (ODQ), and subjective ratings of back pain, leg pain, and disability. Spearman rank correlation coefficient was used to determine if ROM was correlated with clinical outcome. Patients were divided into 2 groups by motion (<= 5 degrees and > 5 degrees). Statistical differences in outcome were sought. Results. Spearman rank correlation coefficient revealed weak-to-moderate but statistically significant associations between ROM and outcome for postoperative back pain (r = -0.35, P = 0.034), ODQ (r = -0.33, P = 0.046), and modified Stauffer-Coventry scores (r = 0.42, P = 0.0095). Patients with motion of > 5 degrees had superior outcomes in ODQ (mean difference 12.6 points, P = 0.026) and Stauffer-Coventry scores (mean difference 2.2 points, P = 0.015). Conclusions. The radiographic ROM at 8.6-year follow-up was positively correlated with several outcomes measures. Patients with motion > 5 degrees had clinically modest but statistically better outcomes in ODQ and modified Stauffer-Coventry scores. Longer follow-ups will be necessary to measure fully the impact of TDR ROM on outcome.