Objective To evaluate the effect of modified Ilizarov device combined with minimally invasive osteotomy in the treatment of genu varum deformity.Methods From February 2002 to May 2010,a total of 31 patients with genu varum deformity who had underwent corrections by using modified Ilizarov device combined with minimally invasive osteotomy were retrospectively analyzed,including 8 males and 23 females with an average age of 35.6 years (range,18-69 years).Fifty-six knees were involved in the 31 patients.Preoperative angle of genu varum was 17.0° ±8.8°.According to the American knee society score (KSS),preoperative score was about 34-100 point with an average of 86.2±18.5.After determining the center of rotation angulation,osteotomy was performed in the site of tibial deformity and below the fibular head with minimally invasive device respectively.Prepared modified Ilizarov device was assembled and fixed with kirschner wire.Then genu varum deformity was progressively corrected by adjusting the length of bilateral bolts.X-ray film,KSS score,subjective sensation,and occurrence of complication were used to evaluate the therapeutic effects.Results Modified Ilizarov devices were used in 56 knees for 9-20 weeks,all patients were followed up for 14-50.4 months,with an average of 30.5 months.The angle of genu varum deformity was 1.7°±0.9°,the KSS was 96.1±7.7.According to KSS,the results were excellent in 49 knees,good in 6,fair in 1,with the excellent and good rate was 98.2％ (55/56).The complications included pin site infection in 11 patients and pin loosening in 3 ones; they were healed through routine dressing change and replacing pin site respectively.Conclusion Modified Iilizarov device combined with minimally invasive osteotomy for the treatment of genu varum deformity can achieve a satisfactory therapeutic effect.