Department of Joint Surgery, Honghui Hospital, Xi'an Jiaotong University, No. 555 Youyi East Road, Xi'an, 710054, Shaanxi, China.
Department of Orthopedics, Aviation General Hospital, No. 3 Anwaibeiyuan Road, Chaoyang District, Beijing, 100020, China.
BMC Musculoskelet Disord. 2020 Apr 6;21(1):211. doi: 10.1186/s12891-020-03242-0.
Femoral head collapse is the key to the progress of osteonecrosis of the femoral head (ONFH), but the causes of collapse are not completely clear. The better understanding of the progress of femoral head collapse will guide the treatment strategy for ONFH patients. The purpose of this study was to evaluate the biomechanical influence of necrosis area on the collapse of the femoral head by finite element analysis.
CT and MRI data from the hip joint of a healthy volunteer were collected to establish a finite element (FE) model of a normal hip. Subsequently, five categories of osteonecrosis FE models were established by using the normal model and computer software according to China-Japan Friendship Hospital (CJFH) classification for ONFH. The CJFH system includes five types based on the size and location of necrosis lesions in the femoral head (type M, C, L1, L2, and L3) and the stage of ONFH. The collapse indices of each model were analyzed by FE method, including the displacement, peak von Mises stress and stress index of the simulated necrotic area as well as the lateral pillar contact area of the femoral head to acetabular.
(1) The displacement increments in the simulated necrotic areas of type M, C, L1, L2, and L3 models were 3.75 μm, 8.24 μm, 8.47 μm, 18.42 μm, and 20.44 μm respectively; the peak von Mises stress decrements were 1.50 MPa, 3.74 MPa, 3.73 MPa, 4.91 MPa, and 4.92 MPa respectively; and the stress indices were 0.04, 0.08, 0.08, 0.27, and 0.27 respectively. (2) The displacement increments in the lateral pillar contact areas of five type models were significantly different (P < 0.001) and increased in sequence as follows: 1.93 ± 0.15 μm, 5.74 ± 0.92 μm, 5.84 ± 1.42 μm, 14.50 ± 3.00 μm, and 16.43 ± 3.05 μm. The peak von Mises stress decrements were also significantly different (P < 0.001) and increased in sequence as follows: 0.52 ± 0.30 MPa, 0.55 ± 0.12 MPa, 0.67 ± 0.33 MPa, 4.17 ± 0.59 MPa, and 4.19 ± 0.60 MPa. (3) The collapse indices including the displacement increments and peak von Mises stress decrements of type L2 and L3 models were markedly higher than those of type M, C, and L1 models (P < 0.001).
The collapse indices of the femoral heads of type L2 and L3 FE models were significantly higher than those of type M, C, and L1. Different areas of necrosis result in varied impact on the femoral head collapse.
股骨头塌陷是股骨头坏死（ONFH）进展的关键，但塌陷的原因尚不完全清楚。更好地了解股骨头塌陷的进展将指导 ONFH 患者的治疗策略。本研究旨在通过有限元分析评估坏死面积对股骨头塌陷的生物力学影响。
收集一位健康志愿者髋关节的 CT 和 MRI 数据，建立正常髋关节的有限元（FE）模型。随后，根据中日友好医院（CJFH）ONFH 分类，使用正常模型和计算机软件，建立了五类骨坏死 FE 模型。CJFH 系统包括基于股骨头坏死病变大小和位置的五类（M、C、L1、L2 和 L3 型）和 ONFH 分期。通过 FE 方法分析每个模型的塌陷指数，包括模拟坏死区的位移、峰值 von Mises 应力和应力指数以及股骨头外侧柱接触面积到髋臼。
（1）M、C、L1、L2 和 L3 模型模拟坏死区的位移增量分别为 3.75μm、8.24μm、8.47μm、18.42μm 和 20.44μm；峰值 von Mises 应力降幅分别为 1.50MPa、3.74MPa、3.73MPa、4.91MPa 和 4.92MPa；应力指数分别为 0.04、0.08、0.08、0.27 和 0.27。（2）五种类型模型的外侧柱接触区位移增量差异有统计学意义（P<0.001），且呈递增趋势：1.93±0.15μm、5.74±0.92μm、5.84±1.42μm、14.50±3.00μm和 16.43±3.05μm。峰值 von Mises 应力降幅也有显著差异（P<0.001），且呈递增趋势：0.52±0.30MPa、0.55±0.12MPa、0.67±0.33MPa、4.17±0.59MPa 和 4.19±0.60MPa。（3）L2 和 L3 模型的塌陷指数，包括位移增量和峰值 von Mises 应力降幅，明显高于 M、C 和 L1 模型（P<0.001）。
L2 和 L3 型 FE 模型的股骨头塌陷指数明显高于 M、C 和 L1 型。不同的坏死区域对股骨头塌陷的影响不同。
