Predictive Factors for the Outcome of Fusion in Adult Isthmic Spondylolisthesis

Study Design. A prospective study on predictive factors for the outcome of 164 patients with adult isthmic spondylolisthesis operated on with fusion. Objective. In view of the need to better select patients for fusion, we investigated the use of the pain drawing (PD) and other potential factors for predicting the outcome of fusion. Summary of Background Data. Results on predictive factors of outcome after spinal fusion have been contradictory and large, well-defined, patient samples with adequate observation times are lacking. Methods. Questionnaires including possible predictive factors and PDs were obtained before surgery. Degree and level of slip were documented. Outcome was quantified by measurement of pain (VAS), Disability Rating Index, the Oswestry Disability Index, and global assessment by the patient into "much better," better," "unchanged," or "worse. "The 2-year follow-up rate was 160 of 164 (98%). Results. In the total sample 49% of patients were much better, 25% better, 14% unchanged, and 12% worse. The following preoperative factors correlated to a worse outcome in the univariate analysis: not working, no regular exercise, female gender, shortness in stature, and a non-organic PD. The multivariate regression analysis showed that work status was the main determinant of outcome. Gender and exercise had less but significant impact (P = 0.004 and 0.02, respectively). In the multivariate regression analysis the PD was not a significant predictor (P = 0.06). Conclusion. The present study shows that patients working before surgery have a more favorable outcome. Also male gender and regular exercise are indicators of a better outcome after fusion. Female patients not working, not exercising or, if these factors are not known, with nonorganic PDs, should be informed about their suboptimal chances of an excellent outcome after fusion.