Rates of Fusion Procedures following Lumbar Microdiscectomy

Introduction Ten percent of the patients with lumbar herniated disc disease end up having chronic pain and disability from herniation. Microdiscectomy has long been the standard treatment for lumbar disc herniation. Given the high physical stresses experienced by the lumbar spine, there is a risk of adjacent segment disease following microdiscectomy and need for fusion. However, fusion rates in patients who have undergone lumbar microdiscectomy are unknown. Goal of our study was to define the demographic characteristics and the rates of single and multilevel fusions following lumbar microdiscectomy. Materials and Methods The PearlDiver database was searched using ICD-9 diagnostic codes for lumbar disc herniation, disc degeneration, and spinal stenosis from 2007 to 2010 using United Healthcare database. Current Procedural Terminology (CPT) codes were used to identify patients who underwent microdiscectomy and had a single or multilevel lumbar fusions procedure afterwards. Patients were stratified by year of diagnosis, age, and gender. Results In 2007 and 2008, there were 8,374 patients who underwent lumbar microdiscectomy. The average age of patients was 45 years. From those patients, 3.47% (291) required a fusion procedure within the 1st year, 1.8% (151) patients had fusion surgery within 2, and 0.63% (53) within 3 years after microdiscectomy. Across 4 years from 2007 to 2011, the 1-year fusion rate following lumbar microdiscectomy was 3.61%. Conclusion According to our results, a patient's likelihood of requiring a fusion within a year of lumbar microdiscectomy is 3.61%. After 2 years, a patient's likelihood of requiring a fusion decreases significantly. Spinal instability following lumbar microdiscectomy is a potential complication that will occur only in a very small percentage of patient population and should be considered before undergoing operation. Next steps involve analyzing single versus multilevel fusions and separating conditions that can lead to microdiscectomy and fusion.