Internal fixation using a cephalomedullary nail as treatment for proximal femur fracture has recently been popular for early ambulation and rehabilitation. However metal breakage at the lag screw insertion site was reported due to non-union, delayed-union, and early weight bearing. In our orthopedic department, we experienced 2 cases of nail breakage at the lag screw insertion site, therefore we report on evaluation of the cause of metal failure and prevention of complications with literature review.