Fatigue failure stress of the femoral neck. A case report.

Fatigue fractures are frequent injuries in military populations and occur more frequently in joggers in the civilian population. Repetitive stress below failure levels in a time period inadequate to permit remodeling is known to cause fatigue fractures. However, data on stress levels, the number of cycles to failure, and the time interval in in vivo human fatigue fractures is unknown. We recently treated a patient with a fatigue fracture of the femoral neck and were able to determine this data from patient records and finite element stress analysis. From this data we recommend a maximum total distance of 161 km (100 miles) over a three-month interval for runners who are beginning training. Shorter total distance would be advisable for obese patients.