Abstract
Total hip arthroplasty (THA), generally, is planned by applying a template sheet to plain radiographs, and a thorough evaluation of plain radiographs is necessary. However, accurate planning is sometimes difficult, especially in dysplastic hips. To achieve accurate preoperative planning, we have been using 3D-CT template since 2004. Herein, we report the result of our study of 3D-CT based preoperative planning of THA and its problems. The subjects were 22 hips (22 patients) that were preoperatively planned on both plain radiographs (radiographic planning) and 3D-CTs (CT planning). The 22 hips consisted of 20 hips with OA and 2 hips with rheumatoid arthritis. The Crowe classification was Group I for 15 hips, Group II for 3 hips, and Group III for 2. The matching rate was defined to be the rate of complete match between the planned size and the implanted size of the prosthesis. The matching rate of the stem was 59% by radiographic planning and 77% by CT planning, and the matching rate of the cup was 36% by radiographic planning and 73% by CT planning, indicating that both matching rates were higher by CT planning than by radiographic planning. In group I, the matching rate of the cup was 47%(8/17) by radiographic planning and 70%(12/17) by CT planning, while in groups II and III, it was 0%(0/5) by radiographic planning and 80%(4/5) by CT planning, indicating that CT was more useful for accurate planning for severely dysplastic hips. Furthermore, the anteroposterior diameter of the acetabulum, the location of bone spurs and bone defects, and bone morphology, such as the femoral anteversion angle, could be more accurately evaluated by CT planning than by
