Wright David J, Bui Christopher N, Ihn Hansel E, McGarry Michelle H, Lee Thay Q, Scolaro John A
University of California Irvine Department of Orthopedic Surgery, Orange, CA.
Department of Orthopedic Surgery, University of Southern California, Los Angeles, CA; and.
J Orthop Trauma. 2020 Dec 1;34(12):644-649. doi: 10.1097/BOT.0000000000001846.
To evaluate axial fracture obliquity and posterior inferior comminution in vertically oriented femoral neck fractures (FNFs) in the physiologically young patient. A biomechanical investigation was designed to evaluate the impact of these fracture elements on torque to failure using cannulated screw (CS) and sliding hip screw fixation.
Four Pauwels III FNF models were established in synthetic femurs: (1) vertically oriented in the coronal plane (COR), (2) coronal plane with axial obliquity (AX), (3) coronal plane with posterior inferior comminution (CCOM), and (4) coronal plane with axial obliquity and posterior inferior comminution (ACOM). In each group (n = 10), specimens were fixed using either 3 CSs or a sliding hip screw with supplemental antirotation screw (SHS). Quasistatic cyclic ramp-loading to failure was performed using a custom testing jig combining axial preloading and torsional ramp-loading. The primary outcome was torque to failure, defined as angular displacement ≥5 degrees.
In the CS group, torque to failure was 40.2 ± 2.6 Nm, 35.0 ± 1.4 Nm, 29.8 ± 1.5 Nm, and 31.8 ± 2.2 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In the SHS group, torque to failure was 28.6 ± 1.3 Nm, 24.2 ± 1.4 Nm, 21.4 ± 1.2 Nm, and 21.0 ± 0.9 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In both constructs, groups with posterior inferior comminution demonstrated significantly lower torque to failure compared to the COR group (P < 0.05). The CS construct demonstrated higher torque to failure in all groups when compared to the SHS construct (P < 0.01).
Posterior inferior comminution significantly affects torque to failure in vertically oriented FNFs. Three peripherally placed CSs may resist combined axial and torsional loading better than a sliding hip screw construct.
评估生理上年轻患者垂直方向股骨颈骨折（FNFs）的轴向骨折倾斜度和后下粉碎情况。设计一项生物力学研究，以评估这些骨折因素对使用空心螺钉（CS）和滑动髋螺钉固定时的破坏扭矩的影响。
在合成股骨中建立四个 Pauwels III 型 FNF 模型：（1）在冠状面垂直定向（COR），（2）带有轴向倾斜度的冠状面（AX），（3）带有后下粉碎的冠状面（CCOM），以及（4）带有轴向倾斜度和后下粉碎的冠状面（ACOM）。在每组（n = 10）中，标本使用 3 枚 CS 或带补充抗旋转螺钉的滑动髋螺钉（SHS）进行固定。使用结合轴向预加载和扭转斜坡加载的定制测试夹具进行准静态循环斜坡加载直至破坏。主要结果是破坏扭矩，定义为角位移≥5 度。
在 CS 组中，COR、AX、CCOM 和 ACOM 骨折组的破坏扭矩分别为 40.2±2.6 Nm、35.0±1.4 Nm、29.8±1.5 Nm 和 31.8±2.2 Nm（P<0.05）。在 SHS 组中，COR、AX、CCOM 和 ACOM 骨折组的破坏扭矩分别为 28.6±1.3 Nm、24.2±1.4 Nm、21.4±1.2 Nm 和 21.0±0.9 Nm（P<0.05）。在两种固定方式中，与 COR 组相比，后下粉碎组的破坏扭矩均显著降低（P<0.05）。与 SHS 固定方式相比，CS 固定方式在所有组中均表现出更高的破坏扭矩（P<0.01）。
后下粉碎显著影响垂直方向 FNFs 的破坏扭矩。三枚周边放置的 CS 可能比滑动髋螺钉固定方式更好地抵抗轴向和扭转联合载荷。
