Objective To analyze causes for postoperative coxa vara and anti-rotation nail cutting-out after treatment of brittle femoral intertrochanteric fractures with proximal femoral nails ( PFN ).Methods An retrospective study was done on 227 patients with intertrochanteric fracture treated with PFN from June 2006 to February 2009. The causes for postoperative coxa vara and anti-rotation nail cutting-out were analyzed. Harris score was used to evaluate the functional recovery of the hip joint. Results Of all, 221 patients were followed up for 12-48 months (mean 23 months) and six patients were died from serious internal disease within one year. According to Harris evaluation system, the results were excellent and good in 183 patients, fair in 30 and poor in 14. Postoperative coxa vara and anti-rotation nail cuttingout occurred in 16 patients, eight of whom received reoperation to remove internal fixation and skeletal traction at abducent position and the other eight received prosthetic replacement. Conclusions Treatment of proximal femoral fracture with PFN requires a high precision of reduction and operation. Many factors including lateral cortical bone conditions of tuberosity, postoperative patient's cognitive condition,use of improved Jensen-Evans classification and Singh's classification may affect operation outcome.