Fracture risk assessment of vascularized medial femoral condylar bone graft: A finite element analysis

Abstract

Vascularized medial femoral condyle (MFC) bone graft is useful for pseudarthrosis and osteonecrosis, but has the risk of fracture as a complication. This study aimed to create multiple three-dimensional (3D) finite element (FE) femur models to biomechanically evaluate the fracture risk in the donor site of a vascularized MFC bone graft. Computer tomography scans of the femurs of nine patients (four males and five females) with no left femur disease were enrolled in the study. A 3D FE model of the left femur was generated based on the CT images taken from the patients. The descending genicular artery (DGA), the main nutrient vessel in vascularized MFC bone grafts, divides into the proximal transversal branch (TB) and the distal longitudinal branch (LB) before entering the periosteum. Thirty-six different bone defect models with different sizes and locations of the harvested bone were created. The highest stress was observed in the proximal medial and metaphyseal portions under axial and external rotation, respectively. In the bone defect model, the stress was most elevated in the extracted region's anterior or posterior superior part. Stress increased depending on proximal location and harvested bone size. Increasing the size of the bone graft proximally raises the stress at the site of bone extraction. For bone grafting to non-load-bearing areas, bone grafting distally using LB can reduce fracture risk. If TB necessitates a larger proximal bone extraction, it is advisable to avoid postoperative rotational loads.