Background: During fixation of total hip arthroplasty (THA) after osteotomy, it is difficult to obtain a good cement mantle with a cemented stem and to obtain good fit along the medullary canal with a ready-made stem. We developed a CT-based custom stem, which was inserted after osteotomy in THA. Methods: We investigated 32 hips in 28 patients. The mean patient age at surgery was 62 and the mean follow-up period was 13 years. The previous osteotomy was intertrochanteric varus femoral osteotomy in 14 hips, intertrochanteric valgus femoral osteotomy in 17, and Schanz osteotomy in one. CT studies were obtained with a 5 mm slice intervals and 2 mm slice width. We produced stems made of Ti-6Al-4V. The stems did not have collars and the proximal third was coated with a 400-μ. m-thick porous coating covered with 20-μ m-hydroxyapatite (HA) coating. Results: The Harris Hip Score improved from a preoperative mean of 49.9 points to a postoperative mean of 82.7 points. One patient complained of postoperative thigh pain. Fractures occurred in two hips. Dislocation occurred in three patients. To date. no patient has reqired revision of the stem due to aseptic loosening. There was bone-ingrown fixation in all hips. Severe stress shielding was found in 14 hips (44%) Conclusion: Stable fixation was achieved with the proximal press-fit of the custom stem. Although stress shielding was observed in 14 hips, excellent results were obtained over a follow-up period of 10 years with this custom stem system for hips after intertrochanteric femoral osteotomy.博士（医学）・乙第1419号・平成30年6月27
