Abstract

This case report discusses six cases of liner dissociation with the Pinnacle acetabulum following primary total hip arthroplasty. Cases involved a 54mm, 55mm, 56mm or 58mm Pinnacle cup with a neutral polyethylene liner and a 28mm femoral head with either an uncemented Corail or cemented C-Stem femoral prosthesis. Liner dissociation occurred between six months and 19 months post-operatively and all cases occurred following hip flexion. Revision involved replacement of the dissociated liners with either a neutral or lipped liner (Pinnacle or Ultamet polyethylene or metal) and in four of the six cases the femoral head size was increased. In all six cases the dissociated liners were found to have three of the six peripheral locking tabs sheared off. We explore possible causes for liner dissociation.