Causes of cut-out of the lag screw of fixation systems used for lateral fractures of the neck of femur

The purpose of this study is to analyze the causes of cut-out of the lag screw of fixation systems (DHS and γ-nail) used for lateral fractures of the neck of femur. Cut-out of the lag screw occurs during the first 3 months after surgery and it is usually due to: 1) eccentric positioning of the lag screw; 2) impossibility to obtain a stable reduction with the risk of varus collapse; 3) inadequate connection between the screw and the cylinder; 4) important osteoporosis. Since osteoporosis is one of most frequent causes of femoral neck fractures and synthesis failure, a biomechanical study is carried out to compare breaking loads of both arthritic and osteoporotic femoral heads.