Abstract: A wedge-shaped spacer usable for varus, valgus, flexion, extension and derotation osteotomies such as corrective osteotomy for femoral shaft deformity, supracondylar osteotomy of the femur, intraarticular osteotomy of the femur, intraarticular osteotomy of the tibia, high tibial osteotomy and subtuberosity osteotomy of the tibia, supramalleolar osteotomy of the tibia and, corrective osteotomy of the calcaneus, is made of a sintered hydroxyapatite provided with a plurality of pores having a pore size of 50 to 250 .mu.m and connected with each other and with the outside through a plurality of capillaries having a thickness of 0.5 to 5 .mu.m, and having a compression strength of 300 kg/cm.sup.