Lumbar total disc replacement: predictors for long-term outcome.

Abstract

We aimed to identify patient characteristics associated with favourable long-term outcomes after lumbar total disc replacement (TDR). We analysed a cohort of 82 patients with degenerative disc and chronic low back pain (LBP) who were treated with TDR and originally participated in a randomised trial comparing TDR and multidisciplinary rehabilitation. Potential predictors were measured at baseline, and the outcomes assessed 8 years after they received allocated treatment. Outcome measures were dichotomised according to whether the participants achieved a clinically important functional improvement (15 points or more on the Oswestry Disability Index, ODI) (primary outcome) and whether they were employed at 8-year follow-up (secondary outcome). Associations between potential predictors and outcomes were modelled using logistic regression. For the secondary outcome, the results were also organised in a prediction matrix and expressed as probabilities. For 71 patients treated with TDR according to protocol, the follow-up time was 8 years. For a subgroup of 11 patients randomised to rehabilitation who crossed over and received TDR, the median postoperative follow-up time was 72 (range 41-88) months. Of all assessed baseline variables, only presence of Modic changes (type 1 and/or 2) was statistically significantly associated with an improvement of ≥ 15 ODI points. The probability of employment at 8-year follow-up was 1% for patients with ≥ 1 year of sick leave, comorbidity, ODI ≥ 50 and ≤ 9 years of education prior to treatment, and 87% for patients with < 1 year of sick leave, no comorbidity, ODI < 50 and higher education. Patients with Modic changes prior to the TDR surgery were more likely to report a clinically important functional improvement at long-term follow-up. Comorbidity, low level of education, long-term sick leave and high ODI score at baseline were associated with unemployment at long-term follow-up.