Study On The Recovery In Stability After Different Posterior Lumbar Structure Injury

Objective:To study the relationship between the extent in the posterior lumbar structures resection and postoperative lumbar stability,the repair responses to the injured and changes in stability at different post-injury timepoints;To assess the ability and mechanism in self-reparance of stability.Methods:1.Retrospectively analyze the postoperative lumbar stability;2.The injury model includes 3 groups:laminectomy only;laminectomy and left total facetectomy; laminectomy and both facetectomie.At 0,6,12,24,36weeks postinjury,the lumbar specimen were harvested for spiral CT scan and biomechanical testing and histology examination.In biomechanical testing,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 time-points and injury groups.The changes in injuried lumbar were analyzed through radiologic and pathohistologic examinations.The sirus red staining and polarized light microscope used to differentiateâ… andâ…¢type collagen,and the ratio ofâ… /â…¢collagen content can reflect the phase during the repairing course.Results:1.The patients with lumbar stenosis syndrome had good outcome from the decompressive laminectomy,no instability were found in patients with unsatisfied surgery outcome.The outcomes had no correlation with the numbers of facetectomy and laminectomy.2.The sheeps' lumbar stability were destroyed by the 3 types of surgery injuris,especially in flexion/extention and axial rotation.During flexion/extension the decreases in stability were correlate with the injury severity. After at least 6 weeks intervals,the mechanical parameters recovered greatly,and reached to the normal intact levels by 12 weeks,and even exceeded the intact level by 24 and 36 weeks.The pathology examination showed that bone regrowth appeared in the scar tissue,which was consistent with the severity of injury.Scar tissue formed during healing,whose developing and maturating were consistent with the stability recovering.The collagen fibers were disturbed but approximately alligned with the longitudinal axia.The changes of ratio ofâ… /â…¢type collagen had same trend with the changes of stability,contrary to the severity of injuris.Conclusion:Different posterior resection extents without preoperative instability did not cause the appearance of secondary lumbar instability during the follow-up periods, which indicated the ability of life in compensating and repairing the effect of injury. The animal experiments showed that the immediate stabilities were decreased after injuries,but recovered gradually with time,until far exceeded the intact specimens. The recovery of stability is correlated with the healing time.The more severe the injury is,the more slowly the stability regained.Decreasing the tissue injury during operation may benefit the tissue healing and stability regaining.But the strong self-repairing and compensating ability allow the recovery of mechanical lumbar stability after injuries in some extent without fusion or internal fixation.