Hashimoto Jun, Oh Yoto, Yamamoto Kouhei, Yoshii Toshitaka, Fukushima Kazuyuki, Kitagawa Masanobu, Okawa Atsushi
Department of Orthopaedic and Spinal Surgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Department of Orthopaedic and Trauma Research, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Injury. 2024 Jun;55(6):111136. doi: 10.1016/j.injury.2023.111136. Epub 2023 Oct 15.
Although the diagnostic criteria for atypical femoral fracture (AFF) exclude periprosthetic fractures, reports of periprosthetic femoral fractures with characteristics of AFF are rapidly increasing. In this study, we investigated the frequency and pathogenesis of periprosthetic AFF associated with total knee arthroplasty (TKA) based on a theory of AFF subtypes that divides AFFs into two main types: fragility stress fractures of the bowed femoral shaft in the mid-shaft and "typical" subtrochanteric AFFs due to suppression of bone turnover (e.g., by bisphosphonates).
This multicenter prospective study of AFFs was conducted from 2015 through 2022. Clinical, pathological, and morphological characteristics were investigated in patients with periprosthetic AFFs associated only with non-stem TKA. Then, biomechanical investigation of the periprosthetic AFF was performed by computer tomography-based finite element analysis (CT/FEA) using two models with different load axes to examine how the correction of lower limb alignment by TKA influences the tensile stress distribution of the femur and the location of the AFF.
Four of 61 AFFs (6.6%) were identified to be periprosthetic AFF (1 mid-shaft; 3 subtrochanteric). Periprosthetic AFFs had characteristics including mechanical stress due to bowing deformity and potentially suppressed bone turnover due to long-term exposure to specific drugs (e.g., bisphosphonates and glucocorticoids). Although 2 periprosthetic AFFs appeared to involve a bowed femur, one with both of the aforementioned characteristics occurred in the subtrochanteric region, which would be an unusual site for a bowed AFF, and it was demonstrated histologically to have biological activity at the fracture site, suggesting a stress fracture. Furthermore, CT/FEA revealed that tensile stress distribution changed proximally as load axis was shifted laterally according to correction of lower limb alignment by TKA.
Orthopedic surgeons should recognize the presence of TKA-associated periprosthetic AFF caused by various factors including specific drugs, bowing deformity, and lower limb alignment. X-rays of the full-length femurs should be checked regularly after TKA, especially in patients with bowed femurs or long-term exposure to specific drugs.
尽管非典型股骨骨折（AFF）的诊断标准排除了假体周围骨折，但具有AFF特征的假体周围股骨骨折的报告正在迅速增加。在本研究中，我们基于AFF亚型理论，将AFF分为两种主要类型：股骨干中段弯曲的脆性应力性骨折和由于骨转换受抑制（如使用双膦酸盐）导致的“典型”转子下AFF，对全膝关节置换术（TKA）相关的假体周围AFF的发生率和发病机制进行了研究。
这项关于AFF的多中心前瞻性研究于2015年至2022年进行。对仅与非柄型TKA相关的假体周围AFF患者的临床、病理和形态学特征进行了研究。然后，使用具有不同载荷轴的两个模型，通过基于计算机断层扫描的有限元分析（CT/FEA）对假体周围AFF进行生物力学研究，以检查TKA对下肢对线的矫正如何影响股骨的拉应力分布和AFF的位置。
61例AFF中有4例（6.6%）被确定为假体周围AFF（1例股骨干中段；3例转子下）。假体周围AFF具有以下特征：因弯曲畸形产生的机械应力，以及由于长期接触特定药物（如双膦酸盐和糖皮质激素）可能导致的骨转换受抑制。尽管2例假体周围AFF似乎涉及股骨弯曲，但其中1例同时具有上述两种特征，发生在转子下区域，而该区域对于弯曲的AFF来说是一个不寻常的部位，并且组织学检查显示骨折部位具有生物学活性，提示为应力性骨折。此外，CT/FEA显示，随着TKA对下肢对线的矫正使载荷轴向外侧移动，拉应力分布在近端发生变化。
骨科医生应认识到由特定药物、弯曲畸形和下肢对线等多种因素引起的与TKA相关的假体周围AFF的存在。TKA术后应定期检查股骨全长X线片，尤其是对于股骨弯曲或长期接触特定药物的患者。
