锁骨中段1／3骨折不同内固定物及固定方式的生物力学研究

Biomechanical study of different internal fixators and fixation modes for middle 1/3 clavicle frac-tures

目的观察不同内固定物及固定方式对锁骨中段1／3骨折生物力学特性的影响。方法制作人工模型锁骨24根，统一行中段1／3斜形骨折，按临床手术方式予以锁定钢板上位、锁定钢板前下位、重建钢板上位和重建钢板前下位内固定，并在骨折断端粘贴电阻应变片，将试件两端用聚甲基丙烯酸甲酯（polymethyl methaerylate，PMMA）材料包埋固定后，置于Instron-8874液压伺服力学试验测试机上，分别进行压缩、扭转和三点弯曲试验。结果模型锁骨对照组、锁定钢板前下位组、重建钢板前下位组、锁定钢板上位组和重建钢板上位组的抗弯刚度分别为（539．16±47．45）N／mm、（1013．474-121．62）N／mm、（701．06±53．28）N／mm、（360．98±35．37）N／mm和（336．07±18．83）N／mm，对照组、上位组和前位组两两比较差异有统计学意义（P〈0．05）；三点弯曲试验最大挠度值分别为（8．75±0．53）mm、（16．07±1．22）mm、（13．08±0．52）mm、（15．84±0．48）mm和（12．23±0．41）mm，锁定钢板组较重建钢板组的最大挠度值差异有统计学意义（P〈0．05），且均大于对照组（P〈0．05）；扭转试验中，锁定钢板组和重建钢板组向内扭转的扭转刚度分别为（0．77±0．08）Nm／deg和（0．734-0．11）Nm／deg；其向外扭转的平均扭转刚度分别为（0．72±0．07）Nm／deg和（0．75±0．08）Nm／deg，各组间比较差异无统计学意义；各电阻应变值比较内固定组均小于对照组（P〈0．05），尤其锁定钢板前下位组的应变值最小。结论（1）钢板内固定能承担较多的应力，可以起到坚强的支持，利于骨折的早期愈合，是锁骨骨折的首选治疗方法；（2）采用锁定钢板固定于锁骨前下位，具有良好的生物力学特性，并且还有手术简便、低风险、固定牢固、减少术后并发症以及美观等优点，值得临床推广使用。

Objective To investigate the effect of different internal fixators and fixation modes on the biomechanical properties of the middle 1/3 clavicle fractures. Methods Twenty-four artificial clavicle samples were prepared and used to simulate middle 1/3 oblique fractures. According to the clinical operative procedures, fractures were fixed respectively with locking plates in superior position, locking plates in anteroinferior position, reconstruction plates in superior position, and reconstruction plates in anteroinferior position. Then, resistance strain gauges were placed on the broken ends of the bone, embedded in polymethylmethacrylate （PMMA） and placed on Instron-8874 servo-hydraulic mechanical testing machine to have compression test, torsion test, and three-point bending test. Results Bending stiffness of control group, anteroinferior locking plate group, anteroinferior reconstruction plate group, superior locking plategroup and superior reconstruction plate group was （539.16 ± 47.45 ） N/ram, （ 1 013.47 ± 121.62） N/ ram, （701.06 ± 53.28 ） N/ram, （ 360.98 ±35.37 ） N/ram and （ 336.07± 18.83 ） N/mm respectively, with statistical significance in pair comparison among the control, superior, and anterior groups （ P 〈 0. 05）. In three-point bending test, the deflection limit of these groups was （8.75±0.53） ram, （16.07 ± 1.22） mm, （13.08±0.52） mm, （15.8±0.48） ram and （12.23 ±0.41） mm respectively. Moreover, the deflection limit of locking plate group and reconstruction plate group showed significant difference （ P 〈 0.05 ） and both were higher than that in control group （ P 〈 0.05 ）. In torsion test, the mean torsion stiffness of locking plate group and reconstruction plate group was （0.77 ± 0.08） Nm/deg and （ 0.73 ± 0. 11 ） Nm/deg in internal rotation and was （0.72 ± 0.07 ） Nm/deg and （ 0.75 ± 0.08 ） Nm/deg in external rotation, without statistically significant difference between groups. Resistor strain value in internal fixation groups lowered when compared to that in control group （ P 〈 0.05 ） and particularly lower strain value was observed in anteroinferior locking plate group. Conclusions （ 1 ） Plate fixation is the preferred method for treatment of clavicle fractures in that the plate can bear large amount of stress, provide a solid support and facilitate early fracture healing. （2） Anteroinferior clavicle plating using a locking plate possesses good biomechanieal properties and has advantages of easy operation, low risk, solid fixation, few complications and cosmetic improvement. The technique is worthy of clinical practice.