Furui Atsuo, Terada Nobuki, Mito Kazuaki
Department of Orthopaedic Surgery Restorative Medicine of Neuro-Musculoskeletal System, Fujita Health University, Bantane Hospital, 3-6-10 Otoubashi, Nakagawa-ku, Nagoya, Aichi, 454-8509, Japan.
J Orthop Surg Res. 2018 Nov 27;13(1):300. doi: 10.1186/s13018-018-1011-y.
Femoral trochanteric fractures are common among older adults. In the reduction of trochanteric fractures, acquiring the support of the anterior cortex at the fracture site on lateral view immediately after surgery is important. However, even if the cortical support is acquired, postoperative displacement due to the loss of this support often occurs. This study aimed to investigate local stress distribution in several trochanteric fracture models and to evaluate risk factors for postoperative displacement using the finite element (FE) method.
Displaced two-fragment fracture models with an angulation deformity at the fracture site and a non-displaced two-fragment fracture model were constructed. The models with an angulation deformity were of two types, one with the proximal fragment directed backward (type A) and the other with the proximal fragment rotated forward from the femoral neck axis (type B). Thereafter, FE models of the femur and a sliding hip screw mounted on a 135° three-hole side-plate were constructed. A 2010-N load was applied to the femoral head, and a 1086-N load was applied to the greater trochanter. Under this condition, the maximum value of the von Mises stress distribution and the amount of displacement of the femoral head vertex in the distal direction were investigated.
A larger maximum stress value at the medial femoral neck cortex and a higher amount of displacement in the distal direction were particularly recognized in type A models. These results indicate that microstructural damage was larger in type A models and that type A fracture alignment may be particularly related to fracture collapse and subsequent postoperative displacement.
Even if support of the anterior cortex at the fracture site on lateral view is acquired immediately after surgery, caution is necessary for cases in which the proximal fragment is directed backward in the postoperative displacement from the viewpoint of the biomechanics of the FE method.
股骨转子间骨折在老年人中很常见。在转子间骨折复位时，术后立即在侧位片上获得骨折部位前侧皮质的支撑很重要。然而，即使获得了皮质支撑，由于这种支撑的丧失导致的术后移位也经常发生。本研究旨在使用有限元（FE）方法研究几种转子间骨折模型中的局部应力分布，并评估术后移位的危险因素。
构建了骨折部位有角度畸形的移位双骨折块模型和无移位双骨折块模型。有角度畸形的模型有两种类型，一种近端骨折块向后（A型），另一种近端骨折块从股骨颈轴线向前旋转（B型）。此后，构建了股骨和安装在135°三孔侧板上的滑动髋螺钉的有限元模型。向股骨头施加2010-N的载荷，向大转子施加1086-N的载荷。在此条件下，研究了von Mises应力分布的最大值和股骨头顶点向远侧的位移量。
在A型模型中，尤其在股骨颈内侧皮质处观察到更大的最大应力值和更高的向远侧位移量。这些结果表明，A型模型中的微观结构损伤更大，并且A型骨折对线可能与骨折塌陷及随后的术后移位特别相关。
即使术后立即在侧位片上获得了骨折部位前侧皮质的支撑，从有限元方法的生物力学角度来看，对于近端骨折块在术后移位中向后的情况仍需谨慎。
