In revision hip Arthroplasty, there often exists the intact femoral cortex under the level of loosened stem. In such cases we used a mid-length full-porous Cementless stem, because femoral bone remodeling and reinforcement could be obtained. We evaluated the readiographical change in femur after the inplantation of full-porous Cementless stem.

Materials and methods: Thirteen revision hip Arthroplasties with the use of mid-length full-porous Cementless stem (Ostenics Specilty Stem) were evaluated. Before revision operation, aseptic loosening and sinking of femoral stem were seen in all hips. In three hips, varus shift of femoral component was seen, and in one hip, anterior shift was seen. Bone graft was done only around the proximal femoral defect. No bone graft was done at the level of middle and distal bone defect of the femur. The average age at revision operation was 59 (43-75) years old. Average follow up was 32 (15-59) months. All hip were evaluated clinically and radiographically, especially about the femoral cortical bone remodellig after operation.

Results: Ten patients were pain free, and three had thigh pain. Subsidence of the stem occurred in one patient who complained of thigh pain. In this patient, cortical enlargement and thinning of femur was extreme before operation. Other 12 cases have no subsidence of the stem. Ten patients had a satisfactory result in clinically and radiographically. In six patients, who had bone defect of middle and distal femur before operation, the new bone formation between stem and the cortex of the femur was seen at the latest follow up. Femoral bone remodeling was optained in the middle and distal femur without bone graft.

Conclusion: Revision hip Arthroplasty with the use of full porous Cementless stem is a useful option because femoral bone remodeling and reinforcement can be obtained.

We developed K.K.S. (Keio-Kyocera Series) THA sytem. The aim is to develop original THA system suitable for Japanese patients. We produced MCF (means Medullary Canal Filling) stem, based on the anatomical anlysis of Japanese typical osteoarthritic patients (53 cases) by the measurements with CT scan. By the use of this stem, excellent canal fitting and initial rigid fixation can be obtained. We used this stem together with non-cement porous socket from 1992. At first the surface of this stem was smooth (S groupe), from 1994 the surface was altered to porous surface (P groupe), and then from 1995 HA coating to porous surface (H groupe) was added. The purpose of this study is to compare the biological fixation ability among stems with same shape and different surface.

Material and methods: Materials were patients for which Non-cement K.K.S. THA was done, 33 cases, 35 joints. Average age at operation was 55 (43-64) years old. Follow-up terms were 5-8 years. According to stem surface, all cases were divided to 3 groupes (S: 14 joints, P: 10 joints, H: 11 joints) and evaluated clinically and radiographically. The evaluation was done at the point of 5 years after operation for all cases. Clinically existence of thigh pain was evaluated. Radiographically sinking of the stem and osteolysis around femur were evaluated.

Results: Thigh pain was existed on S group: 6/14; 43%, P groupe: 0/10; 0%, H groupe: 2/11; 18%. Stem sinking was seen only on S groupe: 12/14; 84%. Osteolysis was seen only on 1 joint in S groupe. The result of S groupe was apparently poor clinically and radiographically.

Conclusion: To keep the early biological fixation of stem, not only anatomical shape for getting excellent canal fitting but also porous surface structure is needed.