Expansive Suspension Laminoplasty Using a Spinous Process–Splitting Approach for Lumbar Spinal Stenosis: Surgical Technique and Outcomes Over 8 Years of Follow-up

INTRODUCTION: To maximize the benefits of posterior decompression for severe multilevel lumbar spinal stenosis, we refined the expansive laminoplasty technique using a spinous process–splitting approach. This study tests the hypothesis that the surgical benefit of adequate decompression with posterior element preservation is maintained in the long term, over 8 years of follow-up. METHODS: Fifty-eight patients were followed up yearly for 8 years. Eight patients having nonlumbar spine surgery or Parkinson disease were excluded. The noninferiority of the 8-year versus peak-year outcomes was tested, with margins of 5 points for the Oswestry disability index and 1 point for the numeric rating scales (NRSs). RESULTS: In the 50 patients available for follow-up, the peak values of the mean improvements from baseline within the first 7 years were 35.8, 5.7, 5.9, and 2.8 points for the Oswestry disability index, low back pain NRS, leg pain NRS, and leg numbness NRS, respectively. The 95% lower confidence limits for the differences between the mean improvements from baseline at 8 years and the peak year were within the noninferiority margins for each scale. CONCLUSION: Our technique was associated with substantial improvement from baseline for each scale. The initial improvements in function and symptoms were maintained for 8 years.