Failure of the femoral component in the Howse total hip arthroplasty

Fatigue failure of the femoral stem is reported in ten cases of the Howse modification of the Charnley total hip arthroplasty. The overall incidence is comparable to the Charnley original design. Torsional forces are important in the mechanism of failure. Medical cracking (not previously described) was discovered leading to stepped fracture surfaces. Multiple medial cracking has long-term implications for the Howse design. Torsional forces result in oblique fracture lines that are not always visible before surgery. Weight-bearing roentgenograms are advised prior to revision surgery.