Risk Factors for Reoperation in Patients Treated Surgically for Degenerative Spondylolisthesis: A Subanalysis of the 8-year Data From the SPORT Trial.

Study Design. Retrospective analysis of prospective data from the degenerative spondylolisthesis (DS) arm of the Spine Patient Outcomes Research Trial. Objective. The aim of this study was to identify risk factors for reoperation in patients treated surgically for DS and compare outcomes between patients who underwent reoperation with nonreoperative patients. Summary of Background Data. Several studies have examined outcomes following surgery for DS, but few have identified risk factors for reoperation. Methods. Analysis included patients with neurogenic claudication (>12 weeks), clinical neurological signs, spinal stenosis, and DS on standing lateral x-rays. Univariate and multivariate analyses were used to investigate patient characteristics and risk factors. Treatment effects (TEs) were calculated and compared between study groups. Results. Of 406 patients, 72% underwent instrumented fusion, 21% noninstrumented fusion, and 7% decompression alone. At 8 years, the reoperation rate was 22%, of which 28% occurred within 1 year, 54% within 2 years, 70% within 4 years, and 86% within 6 years. The reasons for reoperation included recurrent stenosis or progressive spondylolisthesis (45%), complications such as hematoma, dehiscence, or infection (36%), or new condition (14%). Reoperative patients were younger (62.2 vs. 65.3, P = 0.008). Significant risk factors were use of antidepressants (P = 0.008, hazard ratio [HR] 2.08) or having no neurogenic claudication upon enrollment (P = 0.02, HR 1.82). Patients who were smokers, diabetics, obese, or on workman's compensation were not at greater risk for reoperation. At 8-year follow-up, scores for SF-36 bodily pain (BP), Oswestry Disability Index, American Academy of Orthopaedic Surgeons/Modems version (ODI), and stenosis frequency index were better in nonreoperative patients. TE favored nonreoperative patients for SF-36 BP, physical function, ODI, Stenosis Bothersomeness Index, and satisfaction with symptoms (P< 0.001). Conclusion. The incidence of reoperation for patients with DS was 22% 8 years following surgery. Patients with a history of no neurogenic claudication and patients taking antidepressants were more likely to undergo reoperation. Outcome scores and TE were more favorable in nonreoperative patients.