Effects Of Different Degrees Of Foraminoplasty Just Once Via Percutaneous Endoscopic Lumbar Discectomy On Lumbar Spine Stability

Objective:A three-dimensional finite element model of L355 based on biomechanical characteristics was established,and to analyze the effects of different degrees of foraminoplasty just once via percutaneous endoscopic lumbar discectomy on lumbar spine stability using the finite element method.Methods:A 26-year old healthy Chinese adult male volunteer with no previous history of lumbar diseases was selected.The lumbar spine was scanned by high-resolution 64-slice spiral CT,and the data in lumbar DICOM format were obtained and recorded on CD for storage.Mimics,Geomagic,Solidworks and Ansys software were used to establish the L355 three-dimensional finite element model of normal people,and simulate percutaneous foraminal spine endoscopic surgery at L455 segments,the left ventral articular process of L455 was removed at 1/3,2/3 and 3/3 positions of the circular saw diameter（d=7.5 mm）parallel to the coronal plane and intervertebral disc respectively to establish the L35model after the different degrees of foraminoplasty just once.After applying specific loads and boundary conditions to different models for mechanical analysis,record the range of motion and maximum intervertebral disc stress of the L455 segment of the model after different degrees of foraminoplasty just once under flexion,extension,lateral bending,axial rotation,and compared with the normal model.Results:The L355 three-dimensional finite element model constructed in this study has a realistic appearance,complete structure,and the motion range of the normal L355 model in all directions is consistent with the trend of previous literature.The range of motion and the maximum stress of intervertebral disc of L455 segment did not change significantly under all exercise states after foraminoplasty at 1/3 d and 2/3 d.When foraminoplasty at 3/3 d,the range of motion is larger than normal under right lateral bending and right axial rotation;the maximum stress of the intervertebral disc is larger than normal under right lateral bending and axial rotation,but the lumbar spine did not reach instability.Conclusion:Application of 7.5 mm diameter circular saw for foraminoplasty does not destroy lumbar stability,but there is a tendency for lateral bending and rotational instability when resecting large articular process.The protection of the articular capsule and articular surface should be noted.