股骨颈骨折不同直径加压螺纹钉固定的生物力学研究

Biomechanical study of compression screws with different diameters on fixation strength of femoral neck fracture

目的 :比较不同直径加压螺纹钉内固定股骨颈骨折的效果。方法 :取成人股骨上段防腐标本32例 ,挑选 5例骨密度值相近的标本留用 ,其余 2 7例根据骨密度值配对分成A、B、C、D、E 5组 ,制成股骨颈骨折模型。各组依次用直径 5、6、7、8和 9mm加压螺纹钉内固定后 ,行生物力学实验。将留用的 5例标本分别拧入 5种加压螺纹钉 ,用CT观察螺纹钉对骨质的破坏范围。结果 :随螺纹钉直径增粗 ,各组在扭转 5°时的扭力矩及扭转至屈服时的最大扭力矩有逐渐增加的趋势 ,但无统计学差异 (F =1 .71 1 ,P >0 .0 5;F =2 .40 2 ,P >0 .0 5) ;在股骨头下沉 3mm时的负荷及负载至屈服时的最大负荷逐渐增加 (F =8.391 ,P <0 .0 1 ;F =7.2 6 8,P <0 .0 1 ) ;螺纹钉对骨质的破坏范围随之增大。结论 :在行股骨颈骨折内固定时 ,在保证内固定强度的前提下 ,应选用体积尽可能小的内固定物。

Objective:To evaluate the effect of compression screws with different diameters on fixation strength of femoral neck fracture.Methods:Thirty two embalmed anatomic proximal femurs were collected and five specimens of them with approximate bone density were reserved,while the others were distributed to five groups(named A,B,C,D and E group) by randomized block design according to their bone density.After cervical losteotomy,internal fixation was performed orderly using 5,6,7,8 and 9 mm compression screws.The specimens were tested for torsion and axial loading.Five reserved intact specimens were fixed with the five different screws.The range destroyed by screws was measured using CT.Results:With the screws diameter increasing,there was a tendency that the torque increased when femoral head turned 5°,so did ultimate torque.But there was no significant difference among five groups ( F=1.711,P>0.05;F=2.402,P>0.05); the load increased when femoral head was 3mm down,and there was a significant difference among five groups,so did ultimate load( F=8.391,P<0.01;F=7.268,P<0.01) .But the bone range destroyed by screw increased in pace with the increase of screw's diameter.Conclusions:On fixation of femoral neck fracture,the smaller volume of implant should be chosen based on assuring the fixation strength.