Our study investigated the location and accuracy of osteonecrotic lesions measured by a computed magnetic resonance imaging (MRI, T1-weighted) and coronal data sets in patients with femoral osteonecrosis (ON). A total of 29 patients (38 hips) with ON at the femoral head, who underwent total hip arthroplasty, were recruited into this study. All patients were subjected to MR imaging acquisition before operation. The MRI (T1-weighted) coronal data sets were transferred to a computer in DICOM format using import and export images software (Mimics). A 3D model of ON of the femoral head was restructured. The volume of both femoral heads and the necrotic lesions was calculated. The risk of collapse in patients with different osteonecrotic volume of the femoral head was evaluated using 3D finite element analysis (FEA). Our measurement results showed that the necrotic lesions were located at the anterolateral and superior portion of the femoral head in the restructured 3D model, which matched well with the anatomical location of the osteonecrotic lesions. Our results also revealed that if the necrotic volume was more than 30% of the entire femoral head, there was also a larger collapsed region. Our study suggested that the 3D ON model at the femoral head can be restructured precisely using computed MRI technique. This will be helpful for orthopedic surgeons to understand the shape and location of the necrotic lesion at the femoral head of patients nondestructively.