Fatigue fracture of the femoral neck.

Fatigue fractures in the necks of femurs removed from fresh cadavers were produced experimentally by applying repeated compression and rotational stresses. We found that a load applied once in a physiological direction may be within the ultimate strength of the bone, but may produce a fracture if applied repeatedly. With increased age, chances of fatigue failure increased age, chances of fatigue failure increased and loads of even physiological magnitude produced fatigue fractures. This may also happen during life. The subcapital fractures produced in these specimens were similar to those seen in patients in a clinical practice. This has been reported many times in new young military recruits. In individuals undergoing unusually strenuous exercises, the stress concentrations can be unusually high.