山羊腰椎内固定术中椎弓根螺钉植入深度对邻椎的影响

目的：观察脊柱内固定术中不同椎弓根螺钉植入深度对邻椎生物力学环境和退行性变的影响，探讨椎体内固定强度与邻椎病发生的关系。方法：雄性10月龄玻尔杂交山羊16只，体重为25～30 kg,随机分为对照组(N组)和3组内固定组，每组4只。内固定组建立L₄脊柱不稳定骨折病理模型，以椎弓根螺钉内固定脊柱L₃-L₅节段，按螺钉长度不同分为：长钉组(L组),内固定螺钉长度为25 mm; 中钉组(M组),螺钉长度为20 mm; 短钉组(S组),螺钉长度为15 mm,内固定后进行后路小关节融合；对照组不作任何处理。术后24周，制备对照组与内固定组L₃-S₁腰椎标本，测量上位未融合椎体(L₂)和椎间盘应变和应力，进行影像学、组织学观察，计算MRI指数。结果：与N组相比，L组标本L₂节段椎体、椎间盘的活动和应力均增加(P<0.05),MRI指数未见显着改变(P>0.05),髓核中出现多数退变细胞。M、S组标本上位邻椎受力和髓核退行性改变发生情况不显着(P>0.05).结论：在山羊腰椎内固定融合术中，局部坚强固定可能增加上位未融合节段的活动和承受的应力，促进椎间盘退行性变，导致邻椎病的发生。

Influence of pedicle screws with different insertion depth on neighboring uninfused segments in a goat lumbar spinal fusion model

Objective: To observe the influences of pedicle screws in various insertion depth on the adjacent segment disc degeneration following lumbar spinal fusion. To explore the relationship between the internal fixation rigidity and incidence of adjacent segment disease. Methods: Sixteen hybrid male Bohr goats of 10 months old,weighting between 25 and 30 kg,were randomly devided into a control group(N group),and 3 experimental groups,each group had 4 goats. The L₄ vertebra of each goat in the experimental groups was fractured,L₃-L₅ segments were internal fixed with pedicle screws followed by intervertebral joint fusion by a posterior approach. Three experimental groups were devided according to the length of pedicle screws applied,vertebras of goats in L group were internal fixed by the screws at the length of 25 mm,for M group and S group,20 mm and 15 mm,accordingly. The goats in the control group were treated without any operation. Biomechanical changes and MRI index of upper unfused segment(L₂) were measured 24 weeks after operation,and histological changes were observed as well. Results: The pressure and straining of L₂ vertebral body and intervertebral disc of L group increased more than N group(P<0.05),and degenerated cell counting in nucleus pulposus increased as well(P<0.05). However,MRI index remain unchanged(P>0.05). Conclusions: Rigid internal fixation increases the pressure and straining of vertebral body and intervertebral disc of upper adjacent segment,accelerating the degeneration process following lumbar spinal fusion in goats.