[Experimental study on the mechanism of femoral neck fractures]

To investigate the mechanism of femoral neck fracture, experimental studies were conducted on 48 femurs from 24 cadavers and the relationship between the type of fracture and loss of bone strength due to osteoporosis was investigated. The following results were obtained. 1) Intracapsular fracture was produced with the loading parallel to the axis of the femoral neck and with no applied rotatory force. 2) Among trochanteric fractures, peritrochanteric fracture was produced with rotatory force applied to the femoral head, while intertrochanteric fracture was produced with the loading perpendicular to the femoral shaft. 3) The fracture strength along the seven loading axes on the femoral head decreased with the progress of osteoporosis to the same degree in all directions. The fracture strength on Singh index Grade II, III examples decreased to approximately 1/3-1/4 of Grade VI examples. 4) The type of fracture macroscopically depended upon the direction of the loading, and had no correlation with osteoporosis.