远端锁钉数目对加锁髓内钉力学性能影响的研究

目的　测试远端锁钉数目对加锁髓内钉整体力学性能的影响。　方法　实验共选用国产 TAMZ钛合金制造 9mm胫骨加锁髓内钉 2 0根 ,将所有髓内钉随机分成单钉组 ,远端仅安装 1根锁钉 ;双钉组 ,远端安装 2根锁钉。各组再平均分成两小组 ,将髓内钉安装在自行设计的不锈钢模型中 ,利用万能力学实验机测试各组髓内钉的抗压缩和抗扭转力学特性。　结果　在压缩实验中单钉组平均最大压缩载荷为 1880 N,双钉组的平均最大载荷为 2 16 0 N,两组比较有统计学意义 (P<0 .0 5 ) ;在扭转实验中平均最大扭矩、扭角单钉组分别为 5 5 .5 Nm和 5 8.0°,双钉组分别为 5 5 .8Nm和 5 8.3°,两组无差异 (P>0 .0 5 )。　结论　单根锁钉的力学性质可满足临床要求。临床上安装髓内钉时 ,长管状骨近端或中 1/ 3较稳定的骨折 ,可在远端选择安装 1根锁钉 ;而远端 1/ 3骨折或者粉碎性、伴骨缺损的严重骨折 ,应在远端尽量安装 2根锁钉。

STUDY OF THE IMPACT OF THE NUMBER OF DISTAL LOCKING BOLTS ON THE BIOMECHANICAL FEATURE OF LOCKING INTRAMEDULLARY NAILS

OBJECTIVE: To determine whether the number of distal locking bolts have an impact on the biomechanical feature of locking intramedullary nails. METHODS: Twenty locking nails tested were divided into two groups randomly. One distal locking screw was used in first group (single bolt group); and two were used in the other group (double bolts group). After being fixed in the model, compressive and torsional strength of the interlocking nail were measured in each group. RESULTS: The average maximum strength of double bolts group and single bolt group was 2 160 N and 1 880 N respectively in compression tests(P < 0. 05). In torsion tests, the average maximum torsional moment of double bolts group and single bolt group was 55.8 Nm and 55.5 Nm respectively(P > 0.05), the average maximum torsional angle in double bolts group and single bolt group was 58. 3 degrees and 58.0 respectively(P > 0.05). Conclusion Single distal bolt used in interlocking nail system can meet clinical request, though the whole biomechanical behavior is not better than that of double bolts. One distal bolt is enough for the stable fracture types and double bolts should be used in the serious fracture types.