Objective: To establish the finite element model of spinal canal reconstruction and internal fixation,analysis influence of spinal canal reconstruction and internal fixation on spinal stability,and verify the effectiveness and reliability of spinal canal reconstruction and internal fixation in spinal canal surgery.
Methods: A 30-year-old male healthy volunteer with a height of 172 cm and weight of 75 kg was selected and his lumbar CT data were collected to establish a finite element model of normal lumbar L3-L5,and the results were compared with in vitro solid results and published finite element analysis results to verify the validity of the model. They were divided into normal group,laminectomy group and spinal canal reconstruction group according to different treatment methods. Under the same boundary fixation and physiological load conditions,six kinds of activities were performed,including forward bending,backward extension,left bending,right bending,left rotation and right rotation,and the changes of range of motion (ROM) of L3-L4,L4-L5 segments and overall maximum ROM of L3-L5 were analyzed under the six conditions.
Results: The ROM displacement range of each segment of the constructed L3-L5 finite element model was consistent with the in vitro solid results and previous literature data,which confirms the validity of the model. In L3-L4,ROM of spinal canal reconstruction group was slightly increased than that of normal group during posterior extension(>5% difference),and ROM of other conditions was similar to that of normal group(<5% difference). ROM in laminectomy group was significantly increase than that in normal group and spinal canal reconstruction group under the condition of flexion,extension,left and right rotation. In L4-L5,ROM in spinal canal reconstruction group was similar to that in normal group(<5% difference),while ROM in laminectomy group was significantly higher than that in normal group and spinal canal reconstruction group(>5% difference). In the overall maximum ROM of L3-L5,spinal canal reconstruction group was only slightly higher than normal group under the condition of posterior extension(>5% difference),while laminectomy was significantly higher than normal group and spinal canal reconstruction group under the condition of anterior flexion,posterior extension,left and right rotation(>5% difference). The changes of each segment ROM and overall ROM of L3-L5 showed laminectomy group>spinal canal reconstruction group>normal group.
Conclusion: Laminectomy could seriously affect biomechanical stability of the spine,but application of spinal canal reconstruction and internal fixation could effectively reduce ROM displacement of the responsible segment of spine and maintain its biomechanical stability.
Keywords: Finite element simulation; Laminectomy; Miniplates fixation; Range of motion; Spinal canal reconstruction; Stability.