Bipolar 型人工骨頭置換後に inner head が反復性に脱臼した1例

抄録

We experienced one case of recurrent dislocation of the inner femoral head caused by wear of the bearing insert. The subject a 51 year-old woman with coxarthrosis had received bipolar hip prostheses with a self-centering mechanism approximately seven years earlier. She had been relatively young at the time of her first operation, was engaged in agriculture and enjoyed an active life after this operation. Seven years rater, she developed intermittent severe pain in her hip joint and was occasionally unable to walk. Examination revealed extreme varus alignment of the outer head and a radiolucent zone on the acetabular side. During surgery, we found fixed varus of the outer head, granulation of 3 to 4 millimeters on the acetabulum, and manifest wearing of all inner HDP liner, but failuer of the leaflet was not seen. This suggested that the wear occurred due to impingement of the stem neck with the outer head fixed in varus over giving concentric rotation.
In conclusion, we should be care-ful about treating cases showing progressive varus of the head even when the prevailing bipolar hip pros-thesis with self-centering mechanism was been used.