Dubberley IIA型肱骨小头骨折内固定的有限元分析△

A finite element analysis on 4 types of internal fixation of Dubberley type IIA humeral capitulum fracture

摘要:

[目的] 采用有限元法比较克氏针 (Kirschner wire, KW)、Herbert 螺钉 (Herbert screw, HS)、微钢板 (mini plate, MP)、微钢板+克氏针 (MP-KW)、微钢板+Herbert 螺钉 (MP-HS) 固定 Dubberlery IIA 型肱骨小头骨折的生物力学特点。[方法]采集志愿者的右肘中立位 CT 影像数据，运用 Mimics、3-matic 软件建立 DubberleyIIA 型肱骨小头骨折模型，在此基础上分别建立 KW、HS、MP、MP-KW、MP-HS 固定模型。在 ANSYS 软件中添加不同载荷，分析骨折端位移量及内固定应力分布。 [结果]骨折端位移量，伸直载荷下由大到小依次为 KW＞HS＞MP-KW＞MP-HS [(2.7±0.1) mm, (0.7±0.0) mm, (0.4±0.0) mm, (0.2±0.0) mm, P＜0.05]；屈曲载荷下由大到小依次为 KW＞HS＞MP-KW＞MP-HS [(2.0±0.0) mm, (0.6±0.0) mm, (0.3±0.0) mm, (0.2±0.0) mm, P＜ 0.05]；扭转载荷下依次为 KW＞MP-KW＞HS＞MP-HS [(2.0±0.0) mm, (1.1±0.0) mm, (0.8±0.0) mm, (0.6±0.0) mm, P＜0.05]。骨折线处内固定应力，伸直载荷下由大到小依次为 KW＞HS＞MP-KW＞MP-HS [(8 478.5±30.1) MPa, (1 790.3±33.8) MPa, (1 173.4±32.7) MPa, (645.3±3.5) MPa, P＜0.05]；屈曲载荷下次为 KW＞HS＞MP-KW＞MP-HS [(4 540.2±60.0) MPa, (1 331.9±6.5) MPa, (824.8±4.9) MPa, (450.9±2.7) MPa, P＜0.05]；扭转载荷下依次为 KW＞MP-KW＞HS＞MP-HS [(6 260.4±39.6) MPa, (2 786.6±4.0) MPa, (1 141.0±35.7) MPa, (1 050.9±26.6) MPa, P＜0.05]。[结论] 对于 DubberleyIIA 型肱骨小头骨骨折，微钢板+Herbert 螺钉可提供更好的生物力学稳定性，可以为骨折提供更好的愈合环境。

Abstract:

[Objective] To compare the biomechanical characteristics of internal fixation of Dubberley type IIA humeral capitulum frac- ture with Kirschner wire (KW) , Herbert screw (HS) , mini plate (Mini plate) , mini plate plus Kirschner wire (MP-KW) , mini plate plus Her- bert screw (MP-HS) by finite element method. [Methods] After the CT image data of the right elbow in neutral position were collected from a volunteer, the Mimics and 3-matic software were used to establish a Dubberley type IIA humerus fracture model. On this basis, KW, HS, MP, MP-KW and MP-HS fixation models were established, respectively. As loads were added in ANSYS software, the displacement of frac- ture ends and the stress distributed on the implant of internal fixation were analyzed. [Results] The displacement of fracture ends was ranked up-down as KW＞HS＞MP-KW＞MP-HS [(2.7±0.1) mm, (0.7±0.0) mm, (0.4±0.0) mm, (0.2±0.0) mm, P＜0.05] under straight extension load- ing, while KW＞HS＞MP-KW＞MP-HS [(2.0±0.0) mm, (0.6±0.0) mm, (0.3±0.0) mm, (0.2±0.0) mm, P＜0.05] under flexion loading, and KW＞ MP-KW＞HS＞MP-HS [(2.0±0.0) mm, (1.1±0.0) mm, (0.8±0.0) mm, (0.6±0.0) mm, P＜0.05] under torsion loading. In addition, the Von-Mis- es stress on the implant at fracture line was ranked up-down as KW＞HS＞MP-KW＞MP-HS [(8 478.5±30.1) MPa, (1 790.3±33.8) MPa, (1 173.4±32.7) MPa, (645.3±3.5) MPa, P＜0.05] under straight extension loading, whereas KW＞HS＞MP-KW＞MP-HS [(4 540.2±60.0) MPa, (1 331.9±6.5) MPa, (824.8±4.9) MPa, (450.9±2.7) MPa, P＜0.05] under flexion loading, and KW＞MP-KW＞HS＞MP-HS [(6 260.38±39.6) MPa, (2 786.6±4.0) MPa, (1 141.0±35.7) MPa, (1 050.9±26.6) MPa, P＜0.05] under torsion loading. [Conclusion] For Dubberley type IIA humeral capitulum fracture, mini plates plus Herbert screws provide better biomechanical stability, which might give a better healing envi- ronment for the fracture.