With the improvement of bone substitutes and fixation plates, opening wedge high tibial osteotomy (HTO) has become popular. This study reports a technical approach used in the application of porous β-tricalcium phosphate (β-TCP) blocks for patients undergoing a medial opening wedge HTO. Most of the implanted porous β-TCP can be resorbed. However, a β-TCP block with 75% porosity is inadequate for weight-bearing sites until bone incorporation occurs. Thus, we have recently developed β-TCP block with 60% porosity, which is approximately 7-fold greater in terms of compressive strength than that of β-TCP with 75% porosity. During opening HTO, the opened defect was fixed with a Puddu plate, after which β-TCP with 75% porosity was used to fill the cancellous bone defect, except on the medial cortical bone side where wedge-shaped TCP blocks with 60% porosity were implanted in front and back of the plate. The use of β-TCP blocks with 60% porosity avoided autogenous bone grafting and shortened the surgical time.