Department of Orthopaedic Surgery and Rehabilitation Medicine, SUNY Downstate Medical Center, Brooklyn, NY, USA.
J Orthop Trauma. 2013 Jul;27(7):373-8. doi: 10.1097/BOT.0b013e31827cd5bd.
Unstable intertrochanteric fractures in the elderly occur frequently. Several studies have evaluated the biomechanical impact of distally locking long cephalomedullary nails under axial loading; however, the impact of torsional loading has not been investigated. The purpose of this study is to determine the rotational load to failure of unstable intertrochanteric fractures treated with long cephalomedullary nails, with and without distal interlocking.
Eleven paired cadaveric femora treated with long cephalomedullary nails were randomized into 2 groups. Group 1 was left unlocked, whereas group 2 was distally locked. Osteotomies were completed to create unstable 4-part fractures. The femora were anatomically fixed proximally and distally and secured to the biomechanical testing machine to undergo internal rotation. Torque and rotational angle were measured until failure.
The locked group had a mean maximal torsional load of 57.9 ± 19.0 N·m and a mean rotational stiffness of 119.4 ± 35.7 N·m/rad. The femora treated with unlocked nails had a mean maximal torsional load of 29.1 ± 12.2 N·m and a mean rotational stiffness of 77.2 ± 31.3 N·m/rad. Distal locking resulted in a significant increase in maximal rotational load (P = 0.001) and rotational stiffness (P = 0.004) before failure. No significant difference was found in mean rotational angle at failure between groups (26.0 ± 9.6 degrees, P = 0.263).
Maximal torsional load to failure for the unlocked group is within the functional range of rotational loads experienced at the hip for an average adult. The results show that distal locking significantly increases rotational load to failure. The authors highly recommend routine use of distal interlocking screws during cephalomedullary nail placement in unstable intertrochanteric fractures.
老年人股骨转子间不稳定骨折较为常见。已有多项研究评估了轴向加载下远端锁定股骨近端髓内钉的生物力学影响，但尚未研究扭转加载的影响。本研究旨在确定使用和不使用远端锁定治疗股骨转子间不稳定骨折时，发生破坏的扭转负荷。
将 11 对接受股骨近端髓内钉治疗的尸体股骨随机分为 2 组。第 1 组未解锁，第 2 组远端锁定。完成截骨术以创建不稳定的 4 部分骨折。股骨近端和远端解剖固定，并固定在生物力学试验机上进行内旋。测量扭矩和旋转角度，直到发生破坏。
锁定组的最大扭转负荷平均值为 57.9 ± 19.0 N·m，旋转刚度平均值为 119.4 ± 35.7 N·m/rad。未解锁钉治疗的股骨的最大扭转负荷平均值为 29.1 ± 12.2 N·m，旋转刚度平均值为 77.2 ± 31.3 N·m/rad。在发生破坏之前，远端锁定导致最大扭转负荷（P = 0.001）和旋转刚度（P = 0.004）显著增加。两组在破坏时的平均旋转角度无显著差异（26.0 ± 9.6 度，P = 0.263）。
未锁定组的破坏时最大扭转负荷在成人髋关节经历的扭转负荷功能范围内。结果表明，远端锁定显著增加了扭转破坏负荷。作者强烈建议在不稳定股骨转子间骨折中使用股骨近端髓内钉时常规使用远端锁定螺钉。
