BACKGROUND: Trochanteric osteotomies (TO) facilitate exposure and "true hip reconstruction" in complex primary and revision total hip arthroplasty (THA). However, non-union represents a clinically relevant complication. The purpose of the present study was to identify risk factors for trochanteric non-union. METHODS: All cases of THA approached by TO during the past 10 years were analyzed with respect to potential risk factors for non-union. RESULTS: In 298 cases complete data were available for analysis. Trochanteric union occurred in 80.5%, fibrous union in 5.4% and non-union 14.1%. Risk factor analysis revealed a four times higher risk for non-union in anterior trochanteric slide osteotomies compared to extended trochanteric osteotomies and a three times higher risk in cemented versus non-cemented stems. Multiple logistic regression analysis revealed patient's age and use of cement to be independent risk factors for non-union. CONCLUSIONS: Femoral cementation and increasing age negatively influence the union of trochanteric osteotomies.