[Rupture of the metallic lining in bicentric hemi-arthroplasties of the hip. Apropos of 3 cases].

Three cases of rupture of outer shell of biarticular prostheses used for femoral head fractures are reported. Insufficient thickness of this metallic surface is observed at the pole of the cups. The biomechanical forces inducing the rupture of such a defective surface are the result of mobility of the acetabular horns with weight-bearing. This 3-dimensional behavior of the acetabulum may explain the individual variations of mobility of the floating cups.