358 Biomechanical Analysis of the Structural Stability of the Lumbar Spine Following the Extent of Endoscopic Lumbar Foraminotomy and Laminotomy: A Finite Element Analysis

Abstract

INTRODUCTION: Facetectomy as the standard surgical option performed to relieve the patient's symptoms. Recently, endoscopic lumbar foraminotomy shows an alternative to secure space for the spinal nerve to pass through the foramen. However, the biomechanical research on the postoperative structure stability of the spine after endoscopic surgery remains unknown. METHODS: Six types of models were constructed following the graded removal L4 left side of the superior articular process with or without lamina: Type 1: intact model; Type 2: foraminotomy of left-superior dorsal corner of the superior articular process; Type 3: extended foraminotomy of left superior ventral side of the superior articular process; Type 4: left side total facetectomy; Type 5: left side facetectomy and unilateral laminectomy; Type 6: left side facetectomy and laminectomy. RESULTS: From the changes of experiment data in our finite element analysis of simulated endoscopic surgery, the extent of facet removal increases, the mobility and stress distribution of the surgical segment increases. In all loading conditions, the increase rate of the range of motion was the highest in Type 6 in L3-L4 compared to the intact model. The measured increase rate of von Mises s tresses was highest in left lateral bending in types 5 and 6. Furthermore, under other modes of movement, there was no peak von Mises stress differences on Type 1 to Type 4. CONCLUSIONS: In symptomatic lumbar foraminal stenosis, the impact of endoscopic foraminotomy on the stability may be less than those of total facetectomy. There is no significant difference between the standard and extended endoscopic foraminotomy on stability of the lumbar spine.