National Trends in the Use of Fusion Techniques to Treat Degenerative Spondylolisthesis

Study Design. Retrospective review. Objective. (1) To describe change in treatment patterns for degenerative spondylolisthesis (DS). (2) To report regional variation in treatment of DS. (3) To describe variation in surgeon-reported outcomes for DS based on treatment. Summary of Background Data. Spinal stenosis associated with DS is commonly treated with decompression and fusion but little is known about the optimal fusion technique. During a 6-month period, American Board of Orthopaedic Surgery step II candidates submit procedure lists; these lists have been stored in an electronic database since 1999. Methods. The American Board of Orthopaedic Surgery database was retrospectively queried to identify patients who underwent surgery for DS from 1999 to 2011. Included patients underwent uninstrumented fusion, fusion with posterior instrumentation, fusion using interbody device, or decompression without fusion. Utilization of these procedures was analyzed by year and geographic region. Results. The study period included 5639 cases; the annual number of cases doubled during the study period. The percentage of cases treated with interbody fusion (IF) increased significantly throughout the study period, from 13.6% (1999-2001) to 32% (2009-2011) (P < 0.001). The percentage of DS cases treated with posterolateral fusion peaked in 2003 then decreased as the rate of IF increased. In 2011, the rates of posterolateral fusion (40%) and posterolateral fusion with IF (37%) were nearly identical. The Northwest had the highest rate of IF (41%), >10% higher than any other region (P < 0.001) and more than 23% higher than the Southeast (P < 0.001). Conclusion. Despite little evidence guiding treatment strategy for DS, national treatment patterns have changed dramatically during the past 13 years. The rapid adoption of IF and substantial regional variation in treatment utilization patterns raises questions about drivers of change including perceptions about associated fusion rates, the importance of sagittal balance and differential reimbursement.