Abstract：
BACKGROUND: Despite recent advances in implants and surgical techniques, catastrophic and clinical failures in the treatment of intertrochanteric fractures continue to occur, with dire consequences in an overall frail population subset. The aim of the current study is to evaluate the effect of the factors under the surgeons\' control, namely fracture reduction and implant selection, on the biomechanical behavior of fracture fixation constructs.
METHODS: An experimental protocol was conducted with the use of instrumented sawbones, in order to validate the finite element models. The implants used were the Gamma3®and DHS systems. Subsequently, a series of scenaria were considered, including various reduction and implant angle combinations. Data were retrieved concerning the peak cancellous bone stresses around the hip screw and the volume of cancellous bone in the femoral head stressed at critical levels, as well as implant stresses and stresses on the cortical bone of the distal fragment.
RESULTS: All stable fracture models displayed significantly decreased cancellous bone stresses and implant stresses compared to their unstable counterparts, regardless of implant used. The effect of increasing implant angle led to a decrease in implant stresses in all models studied, but had a beneficial effect on the stresses in the cancellous bone of the proximal fragment only in the subgroups of stable fractures with both implants and unstable fractures treated with a cephalomedullary nail (CMN). In unstable fractures anatomically reduced, the use of CMN led to significantly lower peak stresses in the cancellous bone and a smaller volume of bone stressed at critical levels. Increasing the reduction angle by 5 ° led to a significant decrease in both peak stresses and volume of bone stressed at critical levels, more prominent in the sliding hip screw (SHS) models. Decreasing the reduction angle into varus by 5 or 10 ° led to a significant increase in bone and implant stresses regardless of implant used.
CONCLUSIONS: In stable two-part (AO31.A2) fractures the use of the SHS appears to be biomechanically equivalent to CMN. In unstable, anatomically reduced fractures, the use of CMN leads to significantly reduced cancellous bone stresses and decreased rotation of the proximal fragment during loading. A reduction in varus should be avoided at all costs. In unstable fractures treated with SHS a reduction in slight valgus appears to be biomechanically beneficial. The highest implant angle that allows for proper screw position and trajectory in the femoral head should be used for stable fractures with both implants and unstable fractures treated with Gamma3®.
METHODS: An experimental protocol was conducted with the use of instrumented sawbones, in order to validate the finite element models. The implants used were the Gamma3®and DHS systems. Subsequently, a series of scenaria were considered, including various reduction and implant angle combinations. Data were retrieved concerning the peak cancellous bone stresses around the hip screw and the volume of cancellous bone in the femoral head stressed at critical levels, as well as implant stresses and stresses on the cortical bone of the distal fragment.
RESULTS: All stable fracture models displayed significantly decreased cancellous bone stresses and implant stresses compared to their unstable counterparts, regardless of implant used. The effect of increasing implant angle led to a decrease in implant stresses in all models studied, but had a beneficial effect on the stresses in the cancellous bone of the proximal fragment only in the subgroups of stable fractures with both implants and unstable fractures treated with a cephalomedullary nail (CMN). In unstable fractures anatomically reduced, the use of CMN led to significantly lower peak stresses in the cancellous bone and a smaller volume of bone stressed at critical levels. Increasing the reduction angle by 5 ° led to a significant decrease in both peak stresses and volume of bone stressed at critical levels, more prominent in the sliding hip screw (SHS) models. Decreasing the reduction angle into varus by 5 or 10 ° led to a significant increase in bone and implant stresses regardless of implant used.
CONCLUSIONS: In stable two-part (AO31.A2) fractures the use of the SHS appears to be biomechanically equivalent to CMN. In unstable, anatomically reduced fractures, the use of CMN leads to significantly reduced cancellous bone stresses and decreased rotation of the proximal fragment during loading. A reduction in varus should be avoided at all costs. In unstable fractures treated with SHS a reduction in slight valgus appears to be biomechanically beneficial. The highest implant angle that allows for proper screw position and trajectory in the femoral head should be used for stable fractures with both implants and unstable fractures treated with Gamma3®.
摘要：
背景：尽管最近在植入物和外科技术方面取得了进展，在治疗股骨转子间骨折的灾难性和临床失败继续发生，在总体脆弱的人口子集中造成可怕的后果。本研究的目的是评估外科医生控制的因素的影响，即骨折复位和植入物选择，关于骨折固定结构的生物力学行为。
方法：使用仪器锯骨进行实验方案，为了验证有限元模型。使用的植入物是Gamma3®和DHS系统。随后，考虑了一系列的场景，包括各种复位和植入角度的组合。检索了有关髋螺钉周围松质骨应力峰值和股骨头中松质骨体积在临界水平下应力的数据。以及远端碎片皮质骨的植入物应力和应力。
结果：所有稳定骨折模型均显示松质骨应力和植入物应力显著降低，无论使用植入物。在所有研究的模型中，增加植入角度的影响导致植入应力降低，但是仅在使用植入物和使用头髓内钉（CMN）治疗的不稳定骨折的亚组中，对近端碎片的松质骨中的应力具有有益影响。在解剖学上减少的不稳定骨折中，CMN的使用导致松质骨中的峰值应力显着降低，并且在临界水平下应力的骨体积较小。减小角度增加5°会导致峰值应力和临界水平下的骨骼体积显着降低。在滑动髋螺钉（SHS）型号中更为突出。无论使用何种植入物，将复位角减小5或10°都会导致骨骼和植入物应力显着增加。
结论：在稳定的两部分（AO31。A2）骨折SHS的使用似乎在生物力学上等同于CMN。在不稳定的情况下，解剖学上减少的骨折，CMN的使用导致松质骨应力的显着降低和近端碎片在加载过程中的旋转减少。应不惜一切代价避免减少内翻。在用SHS治疗的不稳定骨折中，轻微外翻的减少似乎在生物力学上是有益的。允许在股骨头中正确的螺钉位置和轨迹的最高植入物角度应用于植入物的稳定骨折和用Gamma3®治疗的不稳定骨折。
方法：使用仪器锯骨进行实验方案，为了验证有限元模型。使用的植入物是Gamma3®和DHS系统。随后，考虑了一系列的场景，包括各种复位和植入角度的组合。检索了有关髋螺钉周围松质骨应力峰值和股骨头中松质骨体积在临界水平下应力的数据。以及远端碎片皮质骨的植入物应力和应力。
结果：所有稳定骨折模型均显示松质骨应力和植入物应力显著降低，无论使用植入物。在所有研究的模型中，增加植入角度的影响导致植入应力降低，但是仅在使用植入物和使用头髓内钉（CMN）治疗的不稳定骨折的亚组中，对近端碎片的松质骨中的应力具有有益影响。在解剖学上减少的不稳定骨折中，CMN的使用导致松质骨中的峰值应力显着降低，并且在临界水平下应力的骨体积较小。减小角度增加5°会导致峰值应力和临界水平下的骨骼体积显着降低。在滑动髋螺钉（SHS）型号中更为突出。无论使用何种植入物，将复位角减小5或10°都会导致骨骼和植入物应力显着增加。
结论：在稳定的两部分（AO31。A2）骨折SHS的使用似乎在生物力学上等同于CMN。在不稳定的情况下，解剖学上减少的骨折，CMN的使用导致松质骨应力的显着降低和近端碎片在加载过程中的旋转减少。应不惜一切代价避免减少内翻。在用SHS治疗的不稳定骨折中，轻微外翻的减少似乎在生物力学上是有益的。允许在股骨头中正确的螺钉位置和轨迹的最高植入物角度应用于植入物的稳定骨折和用Gamma3®治疗的不稳定骨折。
