RELATIONSHIP BETWEEN RANGE OF MOTION AND CLINICAL OUTCOME AFTER LUMBAR DISC REPLACEMENT: NINE YEARS FOLLOW-UP

Abstract

Purpose of the study: The theoretical advantage of a disc prosthesis compared with fusion is to preserve spinal mobility. The purpose of our study was to determine the relationship, at nine years follow-up, between range of motion and clinical outcome after lumbar disc replacement.

Material and methods: This retrospective analysis concerned the clinical and radiographic outcome observed in 38 patients who had undergone one- or two-stage disc replacement surgery (51 implanted prostheses). Mean follow-up was 8.6 years (range 6.9–10.7). Clinical outcome was assessed with the Stauffer-Coventry modified score (SCM), the Oswestry score (ODQ) and a visual analog scale (VAS) for lumbar and radicular pain. Flexion-extension range of motion (ROM) was measured on the upright films (Cobb method) at last follow-up. Each clinical element was compared with the ROM (Spearman coefficient of correlation). Two groups of patients were distinguished: high (> 5°) and low ≤ 5°) ROM for comparison with the Mann-Whitney test.

Results: The Spearman coefficient of correlation disclosed a weak to moderate but statistically significant association between ROM, lumbar VAS (r=−0.35, p=0.034), ODQ (r=−0.33, p=0.046), SCM (r=0.42, p=0.0095); but no significant correlation between ROM and radicular VAS (r=−0.12,p=0.48). Patients with greater ROM had better clinical results and ODQ (mean difference 6.3 points, p=0.031) and SCM (mean difference 2.2 points, p=0.017); but no significant difference between the preoperative characteristics in each group (age, sex, weight, surgical history, lumbar and radicular pain, ODQ and SCM).

Discussion: There are no data in the literature comparing range of motion and clinical outcome after lumbar disc replacement. The present study demonstrated a weak to moderate but statistically significant relationship (r=0.35) between range of flexion-extension motion and clinical outcome at nine years. In addition, patients with lesser ROM (< 5°) have slightly less favorable results compared with those with greater ROM (> 5°). This study suggests the preservation of motion has a positive effect on mid-term clinical outcome.

Conclusion: These results need to be confirmed with long-term prospective data comparing discal prosthesis with fusion and non-surgical treatment in order to demonstrate the usefulness of preserving motion on the quality of the clinical outcome.