Range of motion and adjacent level degeneration after lumbar total disc replacement

Abstract

Background context There are no published studies on the relationship between total disc replacement (TDR) motion and the development of adjacent level degeneration (ALD). Because prevention of ALD is the underlying justification for TDR, studies investigating the validity of this concept are essential. Purpose To examine the relationship between range of motion (ROM) and ALD 8.7 years after lumbar TDR. Study design/setting Retrospective radiographic and chart review. Patient sample Forty-two patients 8.7 years after lumbar TDR. Outcome measures Radiographic flexion-extension and ALD. Modified Stauffer-Coventry score. Oswestry Disability Questionnaire. Subjective patient ratings of back pain, leg pain, and disability. Methods We reviewed the flexion-extension radiographs of 42 patients 8.7 years after TDR. Cephalad adjacent levels were evaluated for degeneration: loss of disc space height, anterior osteophyte formation, or dynamic flexion-extension instability. Graphical analysis of motion and the prevalence of ALD was performed. A statistical relationship between ALD and clinical outcome was sought. Results Ten of 42 patients evaluated (24%) had radiographic ALD. The mean motion was 3.8°±2.0°. The patients with ALD had mean motion of 1.6°±1.3° whereas the patients without ALD had motion of 4.7°±4.5° (p=.035). A clear relationship between motion and the presence of ALD at 8.7-year follow-up was observed. Patients with motion 5° or greater (n=13) had a 0% prevalence of ALD. Patients with motion less than 5° (n=29) had a 34% prevalence of ALD (p=.021, odds ratio 13.5). ALD had no statistically significant effect on clinical outcome although the sample size was small. Conclusions At 8.7-year follow-up, the prevalence of ALD after TDR is higher in patients with motion less than 5°. The presence of ALD had no significant effect on clinical outcome, but the sample size was small. These data suggest that patients with significant ROM after lumbar TDR may have reduced risk for radiographic ALD.