ObjectiveTo evaluate the effectiveness of high tibial osteotomy (HTO) assisted by three-dimensional (3-D) printing technology for correction of varus knee with osteoarthritis. MethodBetween January 2014 and June 2015, 16 patients (20 knees) with varus knee and osteoarthritis underwent HTO assisted by 3-D printing technology; a locking compression plate was used for internal fixation after HTO. There were 6 males and 10 females, aged 30-60 years (mean, 45.5 years). The disease duration was 1-10 years (mean, 6.2 years). The unilateral knee was involved in 12 cases and bilateral knees in 4 cases. According to Koshino's staging system, 3 knees were classified as stage I, 7 knees as stage Ⅱ, 8 knees as stage Ⅲ, and 2 knees as stage IV. Preoperative Hospital for Special Surgery (HSS) knee score was 63.8±2.2; the femorotibial angle was (184.8±2.9) °; and Insall-Salvati index was 1.03±0.13. ResultsAll the wounds healed primarily, and no complication of infection, osteofacial compartment syndrom, or deep vein thrombosis was observed. All patients were followed up 6-18 months (mean, 12.6 months). Personal paralysis was observed in 1 case (1 knee), and was cured after expectant treatment. Bone union time was 2.7-3.4 months (mean, 2.9 months). At 6 months after operation, the femorotibial angle was (173.8±2.0) °, showing significant difference when compared with preoperative one (t=11.70, P=0.00) ; Insall-Salvati index was 1.04±0.12, showing no significant difference when compared with preoperative one (t=-0.20, P=0.85) ; and HSS knee score was significantly increased to 88.9±3.1 (t=-25.44, P=0.00) . At last follow-up, the results were excellent in 13 knees, good in 6 knees, fair in 1 knee, and the excellent and good rate was 95%. Conclusions3-D printing cutting block can greatly improve the accuracy of HTO, avoid repeated X-ray and multiple osteotomy, shorten the operation time, and ensure better effectiveness for correction of varus knee with osteoarthritis.