脊柱后方3D融合预防胸腰椎骨折晚期矫正丢失:有限元分析与随机对照试验

Three-Dimensional Fusion of Posterior Spinal Column to Prevent Postoperative Late Correction Loss in Thoracolumbar Fractures:Finite Element Analysis and Randomized Controlled Trial

椎弓根螺钉系统能使胸腰椎骨折椎体高度和矢状面成角获得良好恢复,但是随着下地活动增多或内固定取出后,易发生椎体高度和后凸畸形矫正的丢失。为此,评价双侧关节突和棘突间植骨3D融合对预防胸腰椎骨折合并椎间盘损伤术后晚期矫正丢失的力学机制和临床效果。模拟患者术后内固定取出后状态,建立双侧关节突联合棘突间植骨融合(治疗组模型)和单纯双侧关节突植骨融合(对照组模型)的L1-L2节段的两种外科有限元模型,按照脊柱三柱理论,对模型施加压缩、前屈与后伸荷载。两种外科模型通过治疗组(11例)和对照组(13例)的前瞻性临床随机对照试验,进行放射学检查。治疗组模型的椎间盘竖向压缩位移和应变较对照组模型明显减小,双侧关节突植骨区应力负荷也较对照组模型减小,而且治疗组模型的后柱比对照组模型形成了更加强化的张力带。治疗组在术后晚期的临床试验结果优于对照组,其差异具有统计学意义(P<0.05)。双侧关节突联合棘突间植骨3D融合比单纯双侧关节突植骨融合更能有效重建脊柱三维稳定性,能较好地获得骨性融合,防止术后晚期伤椎高度丢失以及后凸畸形矫正丢失。有限元分析结合小样本临床随机对照试验,有利于外科手术的设计、评价和优化。

To assess the biomechanics and clinical effects of facet joint plus interspinous process graft 3D fusion on preventing postoperative late correct loss in thoracolumbar fractures with disc damage treated with posterior approach. By simulating the internal fixation removal postoperatively,two surgical finite element models of the L1-L2 segments for facet joint plus interspinous process fusion（ treatment group model） and single-level facet joint fusion（ control group model） were established. The compression,flexion and extension were modeled on the basis of a three-column spine theory. The radiologic follow-up of a prospective clinical randomized controlled trial for the treatment group（ 11 cases） and control group（ 13 cases） were conducted to detect clinical effects of these two surgical models. The disc vertical compressive displacement and strain of the treatment group model were significantly reduced when compared to those of the control group model. The stresslevel on bilateral articular process bone graft was decreased. Furthermore,the posterior tension band of the treatment model was stronger and more stable than that of the control model. Accordingly,radiologic follow-up results of the trial at postoperative late stage of the treatment group were significantly better than those of the control group,which had statistically significant difference（ P 〈 0. 05）. Bilateral facet joints plus interspinous process 3D fusion is able to model the three-dimensional spinal stability more effectively than single-level facet joints fusion and was superior in bony fusion to prevent postoperative late correction loss in the patients treated with posterior approach alone. Finite element analysis associated with small randomized controlled trial is useful to design,evaluate and optimize surgical interventions.