ABSTRACT
BACKGROUND:Minimally invasive endoscopic decompression is currently used in the treatment of lumbar spinal stenosis, but there are few studies on the scope of precise laminectomy under the microscope. OBJECTIVE: To explore the influence of precise decompression with different laminectomy zones on lumbar range of motion and stress distribution using the entire degenerative lumbar finite element model. METHODS: A patient with lumbar spinal stenosis was randomly selected. Based on CT data, the lumbar L4-5 segment finite element model (M1) was established using relevant biomechanical software, and the validity was verified. After that, the finite element simulation of fully endoscopic precisely laminectomy decompression operation was performed. Combined with pathological classification of lumbar spinal stenosis, personalized laminectomy decompression aiming at different L4-5 segment stenosis was established, specifically including L4 lamina margin and partial facet joint resection model (M2), L5 lamina margin and partial facet joint resection model (M3), L4/5 lamina margin and partial facet joint resection model (M4), M4+"Over-the-Top" contralateral partial facet joint resection model (M5), and L4/5 lamina margin and over 50% facet jointresection model (M6). The same boundary loading was applied to the various finite element models. The lumbar range of motion and equivalent stress of intervertebral discs were compared under six conditions including flexion, extension, left and right flexion, left and right rotation. RESULTS AND CONCLUSION: (1) Compared with the entire M1 model, ranges of motion of M2, M3, M4 and M5 models were similar under various conditions, but range of motion of M6 model was significantly increased to 151 %-264% scope, especially in the extension and rotational conditions. (2) In terms of the equivalent stress of disc, the M2, M3, M4 and M5 models showed no obvious increasing trend at the anterior, left and right regions under various working conditions. The largest increase of the equivalent stress at posterior and middle disc regions was 53% maximally, but with no significant stress concentration. However, the equivalent stress in total disc regions showed a significant increasing trend in M6 model, especially in flexion condition with the maximum three times of M1 model. (3) Results suggest that extensive laminectomy can significantly affect the stability of the lumbar spine, with the intervertebral disc stress increase at the corresponding segment which is more likely to accelerate segmental degeneration. Minimally invasive endoscopic decompression is precise and controllable. The personalized decompression schemes can be adopted for different types of lumbar spinal stenosis to ensure the surgery effect and effectively maintain the biomechanical characteristics of the segments.