201. The necessity and risk factors of subsequent fusion after decompression alone for lumbar spinal stenosis with lumbar spondylolisthesis: 5 years follow-up in two large populations

BACKGROUND/CONTEXT:Although decompression without fusion is a reasonable surgical treatment option for some patients with lumbar spinal stenosis (LSS) secondary to spondylolisthesis, some of these patients will require secondary surgery for subsequent fusion. Long-term outcome and need for subsequent fusion in patients treated with decompression alone in the setting of lumbar spondylolisthesis remains controversial. PURPOSE:The aim of this study was to examine the rate, timing, and risk factors of subsequent fusion for patients after decompression alone for LSS with spondylolisthesis. STUDY DESIGN/SETTING:A retrospective cohort study. PATIENT SAMPLE:Patients who had LSS with spondylolisthesis and underwent decompression alone at 1 or 2 levels as a primary lumbar surgery with more than 5 year follow-up. OUTCOME MEASURES:The rate, timing, and risk factors for subsequent fusion. METHODS:Subjects were extracted from both public and private insurance resources in a nationwide insurer database. Risk factors for subsequent fusion were evaluated by multivariate cox proportion-hazard regression controlling for age, gender, comorbidities and the presence or absence of claudication. RESULTS:Five thousand eight hundred and seventy-five patients in the public insurance population (PI population) and 1,456 patients in the private insurance population (PrI population) were included in this study. The rates of patients who needed subsequent fusion were 1.9% at 1 year, 3.5% at 2 years, and 6.7% at 5 years in the PI population, whereas they were 4.3% at 1 year, 8.9% at 2 years, 14.6% at 5 years in the PrI population. The time to subsequent fusion was 730 (365-1234) days in the PI population and 588 (300-998) days in the PrI population. Age less than 70 years, presence of neurogenic claudication and rheumatoid arthritis (RA)/collagen vascular diseases (CVD) were independent risk factors for subsequent fusion in both populations. CONCLUSIONS:Decompression surgery alone can demonstrate good outcomes in some patients with LSS with spondylolisthesis. It is important for surgeons to recognize, however, that patient age less than 70 years, symptomatic neurogenic claudication, and presence of RA and/or CVD are significant independent factors associated with greater likelihood of needing secondary fusion surgery.