Rare fracture of a total hip replacement.

Material fractures in the femoral part of total hip replacements, a late complication, are usually observed in the shaft. In our case, a fatigue fracture of the ball-neck weld occurred 8 1/2 years after implantation of the prosthesis because of insufficient weld depth. Additional negative factors proved to be varus implantation and overloading of the prosthesis due to obesity. The weld represented a point of low resistance. Even if major traumatic events are responsible for the fracture or loosening of an endoprosthesis, overloading (i.e., multiple "microtrauma") is also an important contributing factor.