An Yuzhang, Jiang Dianming
Department of Orthopaedics, the First Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2023 Jun 15;37(6):688-693. doi: 10.7507/1002-1892.202302100.
The biomechanical characteristics of three internal fixation modes for femoral subtrochanteric spiral fracture in osteoporotic patients were compared and analyzed by finite element technology, so as to provide the basis for the optimization of fixation methods for femoral subtrochanteric spiral fracture.
Ten female patients with osteoporosis and femoral subtrochanteric spiral fractures caused by trauma, aged 65-75 years old, with a height of 160-170 cm and a body weight mass of 60-70 kg, were selected as the study subjects. The femur was scanned by spiral CT and a three-dimensional model of the femur was established by digital technology. The computer aided design models of proximal intramedullary nail (PFN), proximal femoral locking plate (PFLP), and the combination of the two (PFLP+PFN) were constructed under the condition of subtrochanteric fracture. Then the same load of 500 N was applied to the femoral head, and the stress distribution of the internal fixators, the stress distribution of the femur, and the displacement of femur after fracture fixation were compared and analyzed under the three finite element internal fixation modes, so as to evaluate the fixation effect.
In the PFLP fixation mode, the stress of the plate was mainly concentrated in the main screw channel, the stresses of the different part of the plate were not equal, and gradually decreased from the head to the tail. In the PFN fixation mode, the stress was concentrated in the upper part of the lateral middle segment. In the PFLP+PFN fixation mode, the maximum stress appeared between the first and the second screws in the lower segment, and the maximum stress appeared in the lateral part of the middle segment of the PFN. The maximum stress of PFLP+PFN fixation mode was significantly higher than that of PFLP fixation mode, but significantly lower than that of PFN fixation mode ( <0.05). In PFLP and PFN fixation modes, the maximum stress of femur appeared in the medial and lateral cortical bone of the middle femur and the lower side of the lowest screw. In PFLP+PFN fixation mode, the stress of femur concentrated in the medial and lateral of the middle femur. There was no significant difference in the maximum stress of femur among the three finite element fixation modes ( >0.05). The maximum displacement occurred at the femoral head after three finite element fixation modes were used to fix subtrochanteric femoral fractures. The maximum displacement of femur in PFLP fixation mode was the largest, followed by PFN, and PFLP+PFN was the minimum, with significant differences ( <0.05).
Under static loading conditions, the PFLP+PFN fixation mode produces the smallest maximum displacement when compared with the single PFN and PFLP fixation modes, but its maximum plate stress is greater than the single PFN and PFLP fixation mode, suggesting that the combination mode has higher stability, but the plate load is greater, and the possibility of fixation failure is higher.
采用有限元技术比较分析骨质疏松患者股骨转子下螺旋骨折三种内固定方式的生物力学特性，为股骨转子下螺旋骨折内固定方式的优化提供依据。
选取10例65 - 75岁、身高160 - 170 cm、体质量60 - 70 kg的女性骨质疏松性股骨转子下螺旋骨折患者作为研究对象。采用螺旋CT扫描股骨，通过数字技术建立股骨三维模型。在转子下骨折状态下构建近端髓内钉（PFN）、股骨近端锁定钢板（PFLP）以及二者联合（PFLP + PFN）的计算机辅助设计模型。然后在股骨头施加500 N的相同载荷，比较分析三种有限元内固定方式下内固定物的应力分布、股骨的应力分布以及骨折固定后股骨的位移，以评估固定效果。
在PFLP固定方式中，钢板应力主要集中在主钉通道，钢板不同部位应力不等，从头端到尾端逐渐减小。在PFN固定方式中，应力集中在外侧中段上部。在PFLP + PFN固定方式中，最大应力出现在下段第一和第二枚螺钉之间，且PFN中段外侧出现最大应力。PFLP + PFN固定方式的最大应力显著高于PFLP固定方式，但显著低于PFN固定方式（<0.05）。在PFLP和PFN固定方式中，股骨最大应力出现在股骨中段的内侧和外侧皮质骨以及最下端螺钉下方。在PFLP + PFN固定方式中，股骨应力集中在股骨中段的内侧和外侧。三种有限元固定方式下股骨最大应力无显著差异（>0.05）。三种有限元固定方式用于固定股骨转子下骨折后，最大位移均出现在股骨头。PFLP固定方式下股骨最大位移最大，其次是PFN，PFLP + PFN最小，差异有统计学意义（<0.05）。
在静态载荷条件下，与单一PFN和PFLP固定方式相比，PFLP + PFN固定方式产生的最大位移最小，但其最大钢板应力大于单一PFN和PFLP固定方式，提示联合方式具有较高的稳定性，但钢板负荷较大，固定失败的可能性较高。
