Objective The study aims to evaluate the biomechanical properties of feline femora with craniocaudal screw-hole defects of increasing diameter, subjected to three-point bending and torsion to failure at two different loading rates.

Study Design Eighty femoral pairs were harvested from adult cat cadavers. For each bending and torsional experiment, there were five groups (n = 8 pairs) of increasing craniocaudal screw-hole defects (intact, 1.5 mm, 2.0 mm, 2.4 mm, 2.7mm). Mid-diaphyseal bicortical defects were created with an appropriate pilot drill-hole and tapped accordingly. Left and right femora of each pair were randomly assigned to a destructive loading protocol at low (10 mm/min; 0.5 degrees/s) or high rates (3,000 mm/min; 90 degrees/s) respectively. Stiffness, load/torque-to-failure, energy-to-failure and fracture morphology were recorded.

Results Defect size to bone diameter ratio was significantly different between defect groups within bending and torsional experiments respectively (intact [0%; 0%], 1.5 mm [17.8%; 17.1%], 2.0 mm [22.8%; 23.5%], 2.4 mm [27.8%; 27.6%], 2.7 mm [31.1%; 32.4%]) (p < 0.001). No significant differences in stiffness and load/torque-to-failure were noted with increasing deficit sizes in all loading conditions. Screw-hole (2.7 mm) defects up to 33% bone diameter had a maximum of 20% reduction in bending and torsional strength compared with intact bone at both loading rates. Stiffness and load/torque-to-failure in both bending and torsion were increased in bones subjected to higher loading rates (p < 0.001).

Conclusion Screw-hole defects up to 2.7 mm did not significantly reduce feline bone failure properties in this ex vivo femoral study. These findings support current screw-size selection guidelines of up to 33% bone diameter as appropriate for use in feline fracture osteosynthesis.

目的 本研究旨在评估猫股骨在两种不同加载速率下三点弯曲和扭转失效的颅尾螺钉孔缺损的生物力学性能。

研究设计 从成年猫尸体中采集了 80 对股骨。对于每个弯曲和扭转实验，有 5 组（n  = 8 对）增加的颅尾螺钉孔缺陷（完整、1.5 毫米、2.0 毫米、2.4 毫米、2.7 毫米）。用适当的先导钻孔制造中骨干双皮质缺损并相应地攻丝。每对的左右股骨被随机分配到分别以低（10 mm/min；0.5°/s）或高速率（3,000 mm/min；90°/s）的破坏性加载协议。记录刚度、载荷/失效扭矩、失效能量和断裂形态。

结果 在弯曲和扭转实验中，缺陷组的缺陷大小与骨直径的比值分别显着不同（完整 [0%; 0%]、1.5 mm [17.8%; 17.1%]、2.0 mm [22.8%; 23.5%]、2.4毫米 [27.8%; 27.6%]、2.7 毫米 [31.1%; 32.4%]) ( p  < 0.001)。在所有载荷条件下，随着缺陷尺寸的增加，刚度和载荷/失效扭矩没有显着差异。在两种负荷率下，与完整骨相比，骨直径高达 33% 的螺钉孔 (2.7 mm) 缺陷的弯曲和扭转强度最多降低 20%。在承受较高载荷率的骨骼中，弯曲和扭转的刚度和载荷/失效扭矩均增加（p  < 0.001）。

结论在这项离体股骨研究 中，高达 2.7 mm 的螺钉孔缺陷并未显着降低猫骨失败的特性。这些发现支持了当前适用于猫骨折接骨术的高达 33% 骨直径的螺钉尺寸选择指南。