Bipolar型人工骨頭でのbearing insertの磨耗に伴うinner headの脱転―そのメカニズムに関する考察

Component Disassembly of Bipolar Prostheses due to Bearing Insert Wear. Discussion of the Mechanism

　Bipolar型人工骨頭の欠点のひとつに，bearing insertの磨耗や破損に伴うinner headの脱転がある．今回われわれは，bearing insertがone touch typeの人工骨頭で2例とleaflet typeの人工骨頭で1例のinner headの脱転を経験したので報告する．対象症例の初回手術時での年齢は50歳，56歳，33歳であった．脱転時の術後経過年数は15年，6年，19年であった．3症例に共通した所見は，bearing insertが全周性に磨耗していたことであった．

　Component disassembly of the inner head due to bearing insert wear or damage is one of the disadvantages of bipolar prostheses. We report 3 cases of component disassembly of the inner head of bipolar prostheses of the hip joint. The age of the patients at the time of first hemiarthroplasty was 50 years, 56 years, and 33 years, respectively. The interval between the first operation and the time when the component disassembly of the inner head occurred was 15 years, 6 years, and 19 years, respectively. The outer cup was the touch type in 2 cases and the leaflet type in 1 case. The bearing insert was found to be worn out in all 3 cases.