Change of clinical and radiological parameters after minimally invasive decompression in patients with lumbar spinal stenosisA 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 radiological 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 radiological data of 20 consecutive patients who were evaluated pre-operatively, at 6-month FU and at 24-month FU. Visual analogue scale (VAS) for back and legs 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), sacral slope (SS) were assessed for each patient. Moreover the percentage variation of clinical and radiological factors at 24-month FU compared to the pre-operative were calculated in order 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 pre-operative values of ODI, LL, SS, PT, SVA significantly affect the 24-month FU values and the percentage improvement of SVA at 24-month FU compared to the pre-operative 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 pre-operative spinal alignment affects the FU one. The improvement of SVA was strictly related to the improvement of LL.