长骨干钻孔深度对接骨螺钉固定强度的影响

目的　研究钢板螺钉固定中的钻孔类型对钉道微观结构和螺钉固定强度的影响。 方法　取8根防腐尸体股骨，每根股骨均布10个钻孔标记并随机分通孔、半通孔两组，钻取通孔、半通孔两种孔型并置入螺钉测试拔出力。两组螺钉置入深度一致，截取骨段量取两组孔型孔位的骨皮质厚度，最后用体视显微镜观察比较孔道骨组织微观结构。 结果　通孔、半通孔组的骨皮质厚度分别为（0.687±0.046）cm、（0.706±0.014）cm，两组间骨皮质厚度无统计学差异；通孔、半通孔组的螺钉拔出力分别为（3.495±0.345）kN、（4.008±0.548）kN，两组间的螺钉拔出力存在统计学差异；通孔、半通孔组钻孔出口侧外环骨板表面撕裂区的平均高度分别为（0.256±0.045）cm、（0.078±0.035）cm，两组间有统计学差异。 结论　钢板螺钉固定钻取孔道时采用半通孔，螺钉置入深度不变，在满足与通孔同样的骨-螺钉接触面积的同时，因出口侧外环骨板破坏较轻，可提供更强的螺钉固定强度。

Effect of long bone borehole depth on screw fixation strength

Objective　To study the effects of borehole patterns on bone microstructure and screw fixation strength in orthopedic plate and screw fixation. 　Methods　Eight anti-corrosive femoral specimens were taken. Each specimen was marked with 10 boreholes and randomly divided into two groups: through-hole and semi-through-hole. Two types of boreholes were drilled and screws were inserted to test pullout force. The depth of screw placement was the same in both groups. The cortical thickness of the two groups of boreholes was taken from the amount of the cut-off bone segment. Finally, the microstructure of the porous bone tissue was observed and compared by stereomicroscope.　Results　 The thickness of bone cortex in through-hole and semi-through-hole groups were (0.687±0.046) cm and (0.706±0.014) cm, respectively. There was no significant difference in the thickness of bone cortex between the two groups. The pull-out force of screw in through-hole and semi-through-hole groups was (3.495±0.345) kN and (4.008±0.548) kN, respectively. There was significant difference in the pull-out force between the two groups. The average height of tear zone on the outer annular bone plate at the exit of through-hole and semi-through-hole groups was (0.256±0.045) cm and (0.078±0.035) cm, respectively, and there was significant difference between the two groups. 　Conclusion　The semi-through holes can be used when steel plate screws were used to fix drilling holes. The depth of screw placement remains unchanged. While meeting the same bone-screw contact area as through holes, it can provide stronger screw fixation strength due to lighter damage of the outer ring bone plate at the outlet side.