Investigative study of Spinal Instrumentation utilizing PLLA (Poly-L-lactide)

采用脊柱骨折和畸形模型进行生物力学和临床研究，以评估脊柱内固定的稳定性和对剩余完整运动节段的影响。传统的基于刚性金属的脊柱内固定器械在骨折和畸形模型中对脊柱提供了有效的满意度。然而，随着器械刚度的增加，相邻完整运动节段上的应力显著增加。此外，脊柱内固定改变了残余运动节段的运动模式，并且随着固定刚度的增加，运动模式的变化变得更加明显。为了克服传统金属内固定的这些负面影响，开发了由金属螺钉和PLLA棒组成的新型脊柱内固定器用于实验研究。在12只绵羊的腰椎中使用PLLA器械进行脊柱融合。共融合24个脊柱节段。四到六个月后，腰椎运动节段被牺牲。尽管PLLA溶解在活体中，但提取的PLLA棒没有显示溶解的证据。为了使PLLA植入物足够稳定以承受脊柱必须承受的载荷，将牺牲PLLA的溶解能力。目前的技术，PLLA器械，具有足够的稳定性，以重建脊柱，而且，溶解特性，以允许有效融合的脊柱节段是很难开发的。需要进一步的研究来开发新的系统。在临床情况下，作者使用PLLA螺钉将植骨固定到植骨部位，用于颈椎疾病的重建。我们分析了30多位接受颈椎融合术的父母。所有患者均获得了牢固融合，与仅移植物而无PLLA螺钉固定相比，显示出更好的临床结果。

Biomechanical and clinical studies were performed to evaluate the stability and the influence of spinal instrumentation on the residual intact motion segments using spinal fracture and deformity models. Conventional rigid metal based spinal instrumentation provided effective satiability to the spine in both fracture and deformity modeles. However, as the rigidity of the instrumentation increased stress on the adjacent intact motion segments significantly increased. Also, spinal instrumentation changes the motion pattern of the residual motion segments, and the changes in the motion pattern become more distinct as the rigidity of the fixation increases. To overcome these negative effects of the conventional metal based instrumentation, new spinal instrumentation consists of metal screws and PLLA rod was developed for experimental investigation. Spinal fusion using PLLA instrumentation was performed in lumber spine of the 12 sheep. Total 24 spinal segments were fused. After four to six months, lumbar motion segments were sacrificed Although PLLA dissolves in the living body, extracted PLLA rods showed no evidence of dissolution. To make PLLA implant stable enough to withstand the load which spine must endure, dissolution ability of the PLLA will be sacrificed. At present technology, PLLA instrumentation which has enough stability to reconstruct the spine and, also, dissolution characteristic to allow effective fusion of the spinal segments is difficult to develop. Further research is required to develop new system. In clinical situation, the authors used PLLA screw for fixation of the bone graft to the graft site in reconstruction of the cervical spine disorders. We have analyzed more than 30 parents who underwent cervical fusion surrey. All patients obtained solid fusion and showed better clinical results compared to only graft without PLLA screw fixation.