人工膝関節置換術における大腿骨頭中心マーキングの重要性―大腿骨コンポーネントの冠状面アライメントの正確性に関する検討

Improved Accuracy of Femoral Component Alignment by a Hip Center Marking Technique in Comparison with Conventional Implantation in Total Knee Arthroplasty

　背景：人工膝関節置換術(TKA)では，コンポーネントを正確なアライメントで設置することが重要であるが，大腿骨コンポーネントを冠状面において機能軸に対し垂直に設置することは容易ではない．

　対象と方法：TKAにおいて大腿骨頭中心をマーキングせずにガイドのみを使用して大腿骨遠位骨切りを行った30例，骨頭中心をマーキングして骨切りを行った30例，ナビゲーションを用いた30例それぞれについて，大腿骨コンポーネントの冠状面設置角度を調査した．

　結果：非マーカー群で87.9±3.7°，マーカー群で89.6±1.0°，ナビ群で90.1±1.3°であり，マーカー群とナビ群では機能軸にほぼ垂直な角度で設置されていた．

　まとめ：TKAにおいては骨頭中心のマーキングは正確なアライメントを獲得するために推奨される方法である．

　Background：This report compares the radiologic results of 3 techniques of femoral component alignment in total knee arthroplasty (TKA) performed by the same surgeon.

　Methods：Femoral component alignment on the coronal plane was compared on the postoperative long-leg radiographs of 3 groups of TKA patients：a group of 30 patients in whom TKA was performed using an intramedullary cutting guide without marking the hip center (Group I), a group of 30 patients in whom TKA was performed using the intramedullary guide and by marking of the hip center (Group II), and a group of 30 patients in whom TKA was performed using a computer navigation system (Group III).

　Results：Component angle to the mechanical axis was 87.9±3.7 degrees in Group I, 89.6±1.0 degrees in Group II, and 90.1±1.3 degrees in Group III.　The alignment in Group I was statistically significantly poorer than in the inferior to other two groups, and the alignment in Group II was as accurate as it was in Group III.　There were no outliers greater than ±3° in Group II or in Group III.

　Conclusions：Since use of an intramedullary cutting guide is an unreliable means of obtaining accurate component alignment, the hip center should be marked prior to surgery and its position should be confirmed during surgery, if an intramedullary cutting guide is applied during TKA.