Modular rotating-hinge knee systemの膝蓋大腿関節の適合について―人工膝関節再置換術例の検討

Adaptation of Patellofemoral Joint of the Modular Rotating Hinge Knee System Following Revision Total Knee Arthroplasty

　人工膝関節（TKA）再置換術に使用したmodular rotating-hinge型TKAの膝蓋大腿関節の適合について検討した．対象は女性6膝（平均年齢76.5歳）で，術後1年に臨床成績（JOAスコア）と膝蓋大腿関節の適合を評価した．JOAスコアは術前36.7点から術後64.2点に改善していた．膝蓋大腿関節は適合良好1膝，傾斜3膝，亜脱臼2膝（33％）であった．膝蓋大腿関節の適合性にはコンポーネントの設置，インプラントのkinematicsや構造など，種々の因子が関与している．

　The purpose of this study was to analyze the adaptation of the patellofemoral (PF) joint of a modular rotating hinge knee system (MRHK) after revision total knee arthroplasty (TKA). We performed revision TKA with the MRHK in six cases (all female). One year after surgery we evaluated the clinical results (JOA score) and the adaptation of the PF joint on radiographs. The clinical results had improved in all six cases. Adaptation of the PF joint was good in 1 patient, fair (lateral tilt) in 3 patients, and poor (subluxation) in 2 patients. Both patients with patellar subluxation experienced moderate pain on standing up and walking up stairs. Poor adaptation of the PF joint of the MRHK after revision TKA appeared to be attributable to postoperative patella baja, malposition of the tibial component, the structure of the implant, and other factors.