Study On The Mechanism Of Lumbar Laminectomy With/without Pedical Screw Fixation Of Sheep

Objective:To study the relationship between lumbar stability and flexibility of fixation in the posterior lumbar, compare postoperative mechanical characteristics of lumbar laminectomy and left half facetectomy with(without) resection of nucleus pulposus of lumbar interertebral disk and pedicle screw fixation.Methods:1. Retrospectively analyze the postoperative lumbar stability.2. The model includes 4 groups:contral group; laminectomy and left half facetectomy; laminectomy and left half facetectomy and resection of nucleus pulposus of lumbar interertebral disk; laminectomy and left half facetectomy and resection of nucleus pulposus of lumbar interertebral disk and pedicle screw fixation. In biomechanical testing, range of motion, the neutral zone, the neutral zone stiffness and elastic zone stiffness in flexion/extention movement, and stiffnesses in lateral bending and axial rotation were caculated and compared among specimens in different groups on 0 or 100N vertical loading. The intervertebral instantaneous center coordinate of rotation were caculated on lateral lumbar flexion and extention X-ray pictures and compared after lumbar one thousand flexion/extention movements on 100N vertical loading on 0.1 Hz rate.Results:1. The patients with lumbar disc herniation had good outcome from the decompressive laminectomy, no instability were found in patients.2. When no vertical loading, difference between the range of motion, the neutral zone, the neutral zone stiffness and elastic zone stiffness of contral group and laminectomy and left half facetectomy with(without) resection of nucleus pulposus of lumbar intervertebral disk in flexion/extention movement were no statistical significance. The range of motion, the neutral zone and the neutral zone stiffness of pedicle screw fixation group were statistical less than other groups, difference between elastic zone stiffness of pedicle screw fixation group and other groups had no statistical significance in flexion/extention movement.3. Elastic zone stiffness of groups had no statistical difference in flexion/extention or bending or rotation movement with 100N vertical loading.4. The intervertebral instantaneous center of rotation of L6S1 of laminectomy and left half facetectomy and resection of nucleus pulposus of lumbar intervertebral disk and pedicle screw fixation groups moved backward after lumbar one thousand flexion/extention movements on 100N vertical loading on 0.1 Hz rate.Conclusion:After laminectomy and left half facetectomy and resection of nucleus pulposus of lumbar intervertebral disk had damaged the posterior lumbar structures, the lumbar stability change had no statistical difference, stress concentration when lumbar moving and adjacent segmental degeneration couldn't happened. But after laminectomy and left half facetectomy and resection of nucleus pulposus of lumbar intervertebral disk and pedicle screw fixation, the lumbar flexibility had descended, stress concentration when lumbar moving and adjacent segmental degeneration had happened.