Clinical outcomes after posterolateral lumbar fusion in workers' compensation patients: a case-control study

Case-control propensity matched.

To compare clinical outcomes after lumbar fusion in patients receiving workers' compensation with a case-matched control group who are not on workers' compensation.

Previous studies have demonstrated poor outcomes in patients receiving workers' compensation after lumbar fusion. However, a case-control study where patients are matched for covariates known to affect outcomes after lumbar fusion, including baseline clinical outcome measures, has not been done.

From 783 patients who underwent posterolateral fusion with complete preoperative and 2-year postoperative outcome measures, 60 patients who were receiving workers' compensation were identified. Outcome measures included the Oswestry Disability Index (ODI), Short Form-36 (SF-36), and back and leg pain numerical rating scales. Propensity scoring technique was used to match these patients with a control group not receiving workers' compensation using sex, age, smoking status, body mass index, diagnosis, number of levels fused, preoperative ODI, SF-36 Physical Component Summary (PCS), SF-36 Mental Component Summary, and back and leg pain scores, producing 58 matched pairs.

There were no significant differences between the demographics, job classification, and preoperative outcome scores in the two groups. At 2 years after operation, patients not receiving workers' compensation had a significantly greater improvement in ODI (P=0.009) and SF-36 PCS (P=0.007) compared with those receiving workers' compensation. Although patients not receiving workers' compensation had greater improvements in back and leg pain compared with those receiving workers' compensation, this did not reach statistical significance (P=0.079). The mean 2-year ODI, SF-36 PCS, and back pain raw scores of patients receiving workers' compensation were significantly lower than those not receiving workers' compensation. Only 19% of workers' compensation patients achieved minimum clinically important difference in terms of ODI compared with 36% of those not receiving workers' compensation (P=0.061). Only 16% of workers' compensation patients achieved SF-36 PCS minimum clinically important difference compared with 40% of those not receiving workers' compensation (P=0.006).

After controlling for covariates known to affect outcomes after lumbar fusion, patients on workers' compensation have significantly less improvement of clinical outcomes in both mean change in ODI and SF-36 PCS, as well as the number of patients achieving substantial clinical benefit. The improvement in back pain was similar between the two groups, but patients on workers' compensation remained more disabled after lumbar fusion. Differences in outcomes may be related to unidentified covariates associated with workers' compensation status.