Change of Clinical and Radiologic Parameters after Minimally Invasive Decompression in Patients with Lumbar Spinal Stenosis. A Prospective Study with Long-term Follow-up

Background The impact of minimally invasive decompression (MID) techniques on spinopelvic parameters and on the sagittal alignment remains a controversial topic. Here we studied the changes in clinical and radiologic parameters and their relationships in a series of lumbar spinal stenosis (LSS) submitted to MID with a minimum follow-up (FU) of 24 months. Methods We prospectively collected clinical and radiologic data of 20 consecutive patients who were evaluated preoperatively, at the 6-month FU, and at the 24-month FU. Visual analog scale (VAS) for back and leg pain, Oswestry disability index (ODI), neck disability index (NDI), sagittal vertical axis (SVA), C7 slope (C7S), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were assessed for each patient. Moreover, the percentage variation of clinical and radiologic factors at the 24-month FU compared with the preoperative factors was calculated to perform correlation studies among these variables. Results We reported a significant improvement of all clinical parameters. A significant increase of LL and SS and a significant decrease of PT and SVA were observed. The preoperative values of ODI, LL, SS, PT, and SVA significantly affect the 24-month FU values, and the percentage improvement of SVA at the 24-month FU compared with the preoperative values was significantly related to the percentage improvement of LL. Conclusions MID is clinically effective in patients with LSS and improves the spinopelvic parameters and the global sagittal balance of the spine. The preoperative spinal alignment affects the spinal alignment at FU. The improvement of SVA was strictly related to the improvement of LL.