Abstract
1. If a vertical load is applied to the head of the femur parallel to its shaft, the upper cortex is stretched and the lower cortex is compressed. The neck breaks from the upper subcapital border to the lesser trochanter. This type of fracture is rarely found clinically.
2. If a compressive force is applied to the area between head and greater trochanter while the head is loaded vertically, a transverse fracture of clinical appearance is produced. If this axial pressure acts along the part of the neck above the central axis a subcapital comminuted fracture results. If the pressure acts below the central axis the result is a transcervical fracture.
3. Strain gauge experiments have shown that axial compression within the upper segment of the neck is produced by the abductor muscles of the hip. Adductor muscles produce a low axial compression. It is suggested that muscular action at the time of injury influences the type of fracture produced by the injury.
