中国骨与关节损伤杂志

目的 通过有限元方法建立锁骨骨折愈合后模型，比较分析不同内固定模型取出内固定后的锁骨生物力学与再骨折风险。方法 收集1名健康志愿者锁骨CT数据，以Dicom格式导入Mimics重建三维模型，采用Solidworks软件将皮质骨与松质骨模型进行装配，构成锁骨模型，并在锁骨模型中段建立斜形骨折和骨痂。构建锁骨中段骨折非手治疗骨愈合模型（A组）、锁骨上方锁定钢板单皮质固定骨愈合取出后模型（B组）、锁骨上方锁定钢板双皮质固定骨愈合取出后模型（C组）、锁骨前下方锁定钢板双皮质固定骨愈合取出后模型（D组），设置边界条件及侧方弯曲载荷，采用最大主应力准则来确定裂纹萌生位置和裂纹拓展路径，当主应力超过116 MPa时单元发生裂纹萌生。结果 A组裂纹形成在肩锁关节面及骨折愈合线内侧前方，B组裂纹出现在内侧钉孔、骨痂线外侧钉孔，C组裂纹出现在骨痂线外侧钉孔、骨痂线内侧依次2个钉孔，D组裂纹出现在骨痂线外侧依次2个钉孔、骨痂线内侧1个钉孔。A组Time 1时刻载荷为207.9 N,Time 2时刻载荷为385.1 N;Time 3时刻载荷为402.9 N,Time 4时刻载荷为436.6 N，锁骨前方骨痂线内侧出现裂纹。B组：Time 1时刻载荷为117.8 N,Time 2时刻载荷为227.4 N,Time 3时刻载荷为227.4 N，骨痂处未出现裂纹。C组Time 1时刻载荷为100.6 N,Time 2时刻载荷为185.1 N,Time 3时刻载荷为237.8 N，骨痂处未出现裂纹。D组Time 1时刻载荷为120.4 N,Time 2时刻载荷为234.9 N,Time 3时刻载荷为234.9 N，骨痂处未出现裂纹。随着侧方弯曲载荷的增加，锁骨发生位移，裂纹拓展终止时4个锁骨模型发生位移。弯曲刚度：A组为23.72 N/mm,B组为21.10 N/mm,C组为19.57 N/mm,D组为19.58 N/mm。结论 在侧方弯曲载荷条件下，锁骨中段骨折愈合移除内固定物后再骨折风险由大到小依次为锁骨前下方锁定钢板双皮质固定骨愈合取出模型、锁骨上方锁定钢板单皮质固定骨愈合取出模型、锁骨上方锁定钢板双皮质固定骨愈合取出模型。

ObjectiveTo establish a finite element model of a healed clavicle fracture and compare the biomechanical properties and refracture risk of the clavicle after removal of different internal fixation constructs.MethodsCT data of the clavicle from a healthy volunteer were collected and imported in Dicom format into Mimics to reconstruct a three-dimensional model.Solidworks software was used to assemble cortical and cancellous bone models into a clavicle model, and an oblique fracture with callus was created in the midshaft of the clavicle. Four models were constructed: a non-surgically treated healed clavicle midshaft fracture model(group A), a model after removal of a superior locking plate with unicortical fixation(group B), a model after removal of a superior locking plate with bicortical fixation(group C), and a model after removal of an anteroinferior locking plate with bicortical fixation(group D). Boundary conditions and lateral bending loads were applied. The maximum principal stress criterion was used to determine crack initiation sites and propagation paths, with crack initiation occurring when the principal stress exceeded 116 MPa.ResultsIn group A, cracks formed on the anterior aspect of the acromioclavicular joint surface and the medial side of the fracture healing line. In group B, cracks appeared at the medial screw hole and the lateral screw hole along the callus line. In group C, cracks occurred at the lateral screw hole along the callus line and sequentially at the two medial screw holes along the callus line. In group D, cracks appeared sequentially at the two lateral screw holes along the callus line and at one medial screw hole along the callus line. In group A, the load was 207.9 N at Time 1, 385.1 N at Time 2, 402.9 N at Time 3, and 436.6 N at Time 4, with cracks appearing medially along the anterior callus line. In group B, the loads were 117.8 N,227.4 N, and 227.4 N at Time 1, Time 2, and Time 3, respectively, with no cracks observed at the callus. In group C, the loads were 100.6 N, 185.1 N, and 237.8 N at Time 1, Time 2, and Time 3, respectively, with no cracks at the callus. In group D, the loads were 120.4 N, 234.9 N, and 234.9 N at Time 1, Time 2, and Time 3, respectively, with no cracks at the callus. As the lateral bending load increased, displacement occurred in the clavicle models, and displacement was observed in all four models when crack propagation terminated. The bending stiffness values were 23.72 N/mm for group A, 21.10 N/mm for group B, 19.57 N/mm for group C, and 19.58 N/mm for group D.ConclusionUnder lateral bending load conditions, the order of refracture risk from highest to lowest after removal of internal fixation for healed midshaft clavicle fractures is as follows: the anteroinferior locking plate with bicortical fixation removal model, the superior locking plate with unicortical fixation removal model, and the superior locking plate with bicortical fixation removal model.