Abstract: Objective To study the application of custom prosthesis replacement in proximal tibia osteosarcoma salvage surgery. Methods Twenty-six patients (12 males and 14 females) aged 11-47 years (mean 18.7 years) admitted to our hospital from September 2005 to June 2008 who underwent joint prosthesis replacement for proximal tibia Ⅱ B osteosarcoma after chemotherapy were retrospectively analyzed. The tumor was 10-18 cm long (mean 14.4 cm). The proximal fibula was involved in 4 out of the 26 patients. Results The patients were followed up for 60-93 months (mean 80.3 months), during which 2 patients (7.7%) had relapse of the tumor after operation and 7 patients died of tumor metastasis with a 5-year disease free survival rate of 73.1%. Joint infection occurred in 3 patients (11.5%) and incomplete common peroneal nerve injury occurred in 1 patient. The average knee extension was delayed 5° (0°-20°). The musculoskeletal tumor society (MSTS) score of knee was 22-30 (mean 25.5). Conclusion Custom prosthetic replacement is an important limb salvage procedure for proximal tibia osteosarcoma with an early reliable stability and a mid-and long-term effect, although it results in a number of complications.