股関節全置換術における寛骨臼固定不全および骨量減少の予測：インシリコとインビトロを組み合わせたアプローチ

Total hip arthroplasty continues to rise in prevalence in both the United States and Europe. The leading cause of revision surgery remains acetabular failure, primarily associated with instability and peri-implant bone loss. This study aimed to investigate bone loss around acetabular components following total hip arthroplasty.

A combined in silico (finite element method, FEM) and in vitro approach was employed to predict short- to mid-term bone loss and assess acetabular implant stability. The FEM model incorporated anatomically realistic geometries of the femur, ilium, and implants (acetabular shell, polyethylene liner, and stem). The in vitro model utilized composite bones instrumented with strain gauges to measure cortical strains. Bone loss and acetabular loosening were simulated in four progressive steps, guided by FEM strain analysis, and reproduced through sequential computer-controlled manufacturing in the in vitro setup to evaluate implant stability. Loading conditions reproduced hip joint forces during gait.

Cortical strain measurements demonstrated strong agreement between the in silico and experimental models (R² = 0.91). Acetabular implantation reduced cortical bone strains by approximately 60% posteriorly and 80% anteriorly. Bone loss was most pronounced in the posterior-superior region and at cortical areas adjacent to the implant-bone interface and represents a volume of 90 mm³. Progressive bone loss reduced implant stability, ultimately leading to component migration up to 1.21 mm and increased contact between the acetabular shell and trabecular bone within the acetabular cavity.

The bone loss simulation effectively demonstrated strain-shielding effects induced by acetabular components. These results, consistent with clinical observations, highlight the need to reconsider acetabular concept design to improve long-term survival rates and reduce the risk of loosening.