Single-Level Lumbar Fusion for Degenerative Disc Disease Is Associated With Worse Outcomes Compared With Fusion for Spondylolisthesis in a Workers' Compensation Setting

Study Design. Retrospective cohort study. Objective. Compare lumbar fusion outcomes, return-to-work (RTW) status in particular, between workers' compensation (WC) subjects undergoing single-level posterolateral fusion for either spondylolisthesis or degenerative disc disease (DDD). Summary of Background Data. Lumbar fusion for spondylolisthesis tends to yield more consistent outcomes than fusion for DDD and discogenic low back pain. Within the clinically distinct WC population, relatively few studies exist that evaluate lumbar fusion outcomes. Methods. A total of 889 Ohio WC subjects were identified that underwent single-level posterolateral lumbar fusion with or without posterior interbody fusion between 1993 and 2010 using Current Procedural Terminology procedural and International Classification of Diseases, Ninth Revision diagnostic codes. Of the total subjects, 269 underwent fusion for spondylolisthesis, and 620 underwent fusion for DDD. Subjects were considered to have returned-to-work (RTW) status within a reasonable timeline if they made a stable RTW within 2 years of fusion and remained working for greater than 6 months of the following year. To determine predictors of RTW status, we performed a multivariate logistic regression analysis. We measured a number of secondary outcomes. Results. Fusion for spondylolisthesis was positively associated with RTW status (P = 0.050; odds ratio [OR], 1.42; 95% confi dence interval [95% CI], 1.00-2.00). A total of 36.4% of the spondylolisthesis cohort and 24.4% of the DDD cohort returned to work in a reasonable timeline postoperatively. Other negative predictors included age more than 50 years at fusion (OR, 0.66; 95% CI, 0.45-0.95), time more than 2 years between injury and index fusion (OR, 0.59; 95% CI, 0.41-0.84), permanent disability (OR, 0.61; 95% CI, 0.43-0.86), legal representation (OR, 0.67; 95% CI, 0.46-0.97), and psychological comorbidity before fusion (OR, 0.30; 95% CI, 0.14-0.62). Subjects in the DDD cohort were prescribed opioid analgesics for an average of 294 of additional days postoperatively (P < 0.001), which equated to 24,759 additional milligrams of morphine equivalents (P < 0.001). Conclusion. Our study is supportive of the conclusion that DDD is a questionable indication for spinal fusion. Given the generally poor outcomes of this study, future studies should determine if lumbar fusion surgery is an effective treatment modality in similar patients with WC.