A Prospective Comparative Study of 2 Minimally Invasive Decompression Procedures for Lumbar Spinal Canal Stenosis Unilateral Laminotomy for Bilateral Decompression (ULBD) Versus Muscle-Preserving Interlaminar Decompression (MILD)

Study Design. A prospective comparative study. Objective. To compare prospectively 2 different types of minimally invasive surgery for lumbar spinal canal stenosis (LSCS): unilateral laminotomy for bilateral decompression (ULBD), and muscle-preserving interlaminar decompression (MILD). Summary of Background Data. Although previous studies have reported several procedures of minimally invasive surgery for the treatment of LSCS, no articles prospectively compared 2 different procedures. Methods. From 2005 to 2009, we prospectively enrolled 50 patients with LSCS for the treatment with ULBD, and 50 patients for MILD. The patients' symptoms were evaluated using Japanese Orthopedic Association (JOA) score, JOA Back Pain Evaluation Questionnaire, and visual analogue scale before and 2 years after operation. For radiological evaluation, changes in disc height, sagittal translation, and lateral wedging at the decompressed segment, as well as lumbar lordosis were investigated using plain radiographs. Results. Ninety-nine of 100 patients were followed for a minimum of 2 years. No significant differences were found in the recovery rate of JOA score, improvement of JOA Back Pain Evaluation Questionnaire, and changes of the visual analogue scale between the 2 groups. Radiologically, no significant differences were present in the postoperative degenerative changes in disc height, sagittal translation, and lateral wedging. In multilevel surgical procedures; however, clinical scores in low back pain, and lumbar function were significantly greater in the ULBD group than those in the MILD group. The lateral wedging change at L2-L3 and L3-L4 more frequently occurred in the ULBD group than in the MILD group. On the contrary, the number of patients who demonstrated the postoperative sagittal translation at L4-L5 was significantly greater in the MILD group than in the ULBD group. Conclusion. Both MILD and ULBD were efficacious procedures for improving neurological symptoms in patients with LSCS. In multilevel decompression surgical procedures, ULBD was superior to MILD in terms of improvement of low back pain and lumbar function at the 2-year time point.