Effect of screw holes on the biomechanics of long tubular bone*☆

Abstract

AIM： To investigate the effect of screw holes remained after removed the internal fixation of plate and nail on the biomechanics of long tubular bone.

METHODS： The experiment was carried out in the laboratory of Department of Orthopedics and Trauma, People's Hospital of Peking University from November 2004 to August 2005. Seventy-six pieces of Sanhuang cock tibia were selected and randomly divided into 7 groups: control group, 1.5 mm unicortical (unilateral cortex was drilled) one hole, bicortical 3 holes and bicortical 5 holes, and 2.5 mm unicortical one hole, bicortical 3 holes and bicortical 5 holes. The control group had normal complete cortex; the 1.5 mm and 2.5 mm unicortical one hole, bicortical 3 holes, and bicortical 5 holes served as corresponding number screw hole models. All the specimens of 7 groups were subjected to single three-points bending test.

RESULT:①When there were bone structure destructions, the maximal bending loads of 1.5 mm unicortical one hole [(16.69±0.66)% of the average outer diameters of tubular bone (transverse diameter+vertical diameter)/2], and bicortical 3 holes did not differed significantly from that of the control group [(366.61±53.23), (364.23±51.26), (362.26±41.40) N, P =0.438, 0.273], but the maximal bending load of 1.5 mm bicortical 5 holes [(314.72±57.61)N] was decreased 13% compared with the control group (P =0.033). ②The maximal bending loads of 2.5 mm unicortical one hole [(29.36±2.07)% of the average outer diameters of tubular bone], bicortical 3 holes and bicortical 5 holes were [(315.55±51.09), (315.83±31.00), (280.81±49.18) N], which decreased 12%, 12% and 22% compared with the control group and there were significant differences (P =0.02, 0.015, 0.001).

CONCLUSION: If the diameter of screw hole on the cortex of long tubular bone is within (16.69±0.66)% of bone cortical outer diameter, and there are only 3 bicortical holes or less, the bending load does not decrease; Once the diameter of screw hole is beyond (29.36±2.07)% of bone cortical outer diameter, the maximal bending load would be decreased apparently. The number of screw holes is not in proportion to the reduction extent of bending load; when there are few bicortical holes, the reduction extent is the same to unicortical one hole.

摘要
目的：探讨板钉内固定物拆除后的螺钉孔对长管状骨的生物力学影响。
方法：实验于2004－11/2005－08在北京大学人民医院创伤骨科实验室完成。取76根三黄鸡胫骨，随机分7组，分别是对照组，1.5 mm孔径的单皮质（只钻透单侧皮质）1孔组、双皮质（钻透双侧皮质）3孔组和双皮质5孔组，以及2.5 mm孔径的单皮质1孔组、双皮质3孔组和双皮质5孔组，对照组即正常的皮质完整组，1.5 mm孔径和2.5 mm孔径的单皮质1孔、双皮质3孔和双皮质5孔组分别作为鸡胫骨中段的直径为1.5 mm和2.5 mm的相应数目的钉道模型, 上述7组标本均进行三点弯曲单一实验。
结果：①1.5 mm的单皮质1孔组[占管状骨平均外径[(横径+纵径)/2]的（16.69±0.66）%]及双皮质3孔组鸡胫骨达到结构破坏时的最大载荷与正常组最大载荷比较差异无显著性[（366.61±53.23），(364.23±51.26)，(362.26±41.40) N，P =0.438，0.273]，双皮质5孔组的最大载荷[(314.72±57.61)N]较正常组降低13%左右（P =0.033）。②2.5 mm的单皮质1孔组[占管状骨平均外径的（29.36±2.07）%]、双皮质3孔组和双皮质5孔组的最大载荷[依次为（315.55±51.09），（315.83±31.00），（280.81±49.18）N]较正常组分别降低12%，12%，22%左右，差异有显著性（P =0.02，0.015，0.001）。
结论：长管状骨皮质上的螺钉孔直径在管状骨外径的（16.69±0.66）%以内，且穿过双侧皮质的钉孔数量为3个以下时，可不影响其弯曲性能；当螺钉孔直径超过管状骨外径的（29.36±2.07）%时，将降低长管状骨的弯曲负荷。钉孔数目与弯曲载荷降低的幅度并不呈比例，双皮质钉孔数目较少时载荷的降低幅度与单皮质1孔大致相同。
关键词：骨螺丝；骨折；生物力学

杨明，姜保国，张殿英，付中国，陈建海，张宏波.螺钉孔对长管状骨生物力学的影响[J].中国组织工程研究与临床康复，2007，11(1):21-24
[www.zglckf.com/zglckf/ejournal/upfiles/07-1/1k-21(ps).pdf]