有限元法及I-Scan测试系统分析尺骨成角截骨后肱桡关节的应力分布

摘要

BACKGROUND: Ulnar osteotomy is firstly recommended for the therapy of Monteggia fracture in children. But,there is still a lack of biomechanical evidence to confirm its efficacy and safety. OBJECTIVE: To analyze the stress distribution on the humeroradial joint after ulnar osteotomy and to provide evidence for confirming the angular size and mechanism for ulnar osteotomy. METHODS: Nine elbow joints were subjected to different positions of physiological, posterior 15° and posterior 30° osteotomy, followed by loaded at different flexion angles in the neutral, pronation and supination positions, respectively, and then the detailed stress distribution and area in the humeroradial joint were obtained using I-Scan Stress Distribution Test system. One elbow joint was scanned by three-dimensional reconstruction CT and the three-dimensional finite element model was established by ANSYS software. The model was loaded with the same conditions based on the I-Scan Test RESULTS AND CONCLUSION: (1) I-Scan Test system showed that the stress concentration area was in the medial side of humeroradial joint when elbow joint extended after the posterior osteotomy. Following the buckling angle of elbows increased, the area of stress concentration was changed to posterior and stress and contact area of humeroradial joint decreased correspondingly. An increase of stress and decrease of contact area appeared after posterior osteotomy compared with physiological osteotomy. (2) According to the finite element analysis, after posterior 15° and 30° osteotomy, pressure of humeroradial joint concentrated in medial-posterior region and the stress was increased. (3) To conclude, ulnar posterior 30° osteotomy is superior to 15° in reducing the incidence of radial head redislocation of Monteggia fracture, but may induce osteoarthritis of humeroradial joint.%背景:尺骨成角截骨矫形是治疗小儿孟氏骨折的首选手术方式,但仍然缺乏足够的生物力学证据证实其有效性及安全性.目的:采用 I-Scan测试系统以及有限元法分析尺骨成角截骨后肱桡关节的应力分布,为确定尺骨成角截骨角度及阐明成角截骨机制提供实验依据.方法:采用9个肘关节标本,分别作生理角度截骨、后侧成角15°以及30°截骨,在中立位、旋前位以及旋后位情况下分别进行0°到90°加载,利用I-Scan传感器获得肱桡关节应力分布及受力面积改变.选取1个标本进行CT三维扫描,并以ANSYS建立由皮质骨组成的有限元模型,加载与I-Scan相同的工况.结果与结论:①I-Scan 测试显示,成角截骨后肘关节伸直时应力集中区在肱桡关节内侧,随着肘关节屈曲角度增加,应力集中区转移至后侧,肱桡关节应力及接触面积减少;后侧成角截骨组比生理角度组肱桡关节应力增加,接触面积减少;应力集中区域的转移,背离孟氏骨折多发的前侧及外侧,能减少桡骨头再脱位的发生,且在应力集中区转移方面分析,后侧成角30°截骨组优势可能大于后侧成角15°截骨;成角截骨后可能增加肱桡关节骨性关节炎风险,其中以后侧成角30°截骨更为明显;②有限元分析显示,后侧成角15°以及30°截骨组肱桡关节应力集中在内后侧;但后侧成角15°以及30°截骨组肱桡关节面压力增加;③综上,尺骨后侧成角30°截骨在防止肱桡关节再脱位上优于后侧成角15°截骨,但是可能增加肱桡关节退行性病变的发生.