人工膝関節表在置換術により、膝蓋後方にどのような変化が生じるか？

[What retropatellar changes result by implantation of a superficial knee joint prosthesis?].

抄録

本研究の目的は、人工膝関節置換術を行った症例における膝蓋後面圧、力、接触面積を、人工膝関節置換術を行っていない膝と比較して評価することである。我々は、人工膝関節置換術の前後で6脚の標本を検討した。修正Thiel固定を用い、人工関節置換術は膝蓋骨インプラント無しのGenesis I（Fa.Smith&Nephew社、Schenefeld）を用いた。接触測定は、感圧フィルム（Fuji Prescale type "super low"）を用い、膝屈曲45度、60度、90度、120度で行った。測定結果は専用ソフトウェア「Pressure Imaging and Analyzing System FPD-901シリーズ」で評価した。脚は股関節を外旋し、膝関節は鞍上アプローチから開脚した。フィルムは、大腿骨の膝蓋面と膝蓋骨の関節面の間の定義された領域に設置された。大腿四頭筋に280Nの力を加え、5秒間の圧力上昇とさらに5秒間の瞬時圧力を測定した。人工膝関節置換術前、接触面積は154.3mm2、平均圧力は1.14MPa、力は182.13Nであった。人工膝関節置換術後、接触面積は119.94mm2、平均圧力は1.522MPa、力は180.98Nであった。人工膝関節置換術後、接触面積は有意に減少し（P = 0.015）、平均圧力（P = 0.0001）と最大圧力（P = 0.0003）は有意に増加した。力は有意に変化しなかった（P = 0.7642）。人工膝関節置換術のインプラントの選択と膝関節へのアプローチは、膝蓋後面の接触面積を増加させ、人工膝関節置換術前よりも接触面積が小さくなるのを防ぐために考慮されるべきである。また、接触面積を増やすことで、人工膝関節置換術後の膝蓋後面圧の上昇を防ぎ、さらなる合併症を防ぐことができる。

The aim of this study was to evaluate the retropatellar pressure, force, and contact area in cases of knee arthroplasty compared to knees without arthroplasty. We examined six leg specimens before and after knee arthroplasty. The modified Thiel fixation was used, and arthroplasty was the Genesis I without patellar implant (Fa. Smith & Nephew, Schenefeld). Contact measurements were performed with pressure-sensitive film (Fuji Prescale type "super low") in 45 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion. The results were evaluated with special software, "Pressure Imaging and Analyzing System FPD-901 Series". The leg was exarticulated in the hip joint and the knee joint was opened from a suprapatellar approach. The film was placed at a defined area between the facies patellaris of the femur and facies articularis of the patella. Instantaneous pressure was measured during a time of 5-s pressure increase and a further 5 s. A force of 280 N was applied to the quadriceps muscle. Before knee arthroplasty, the contact area measured 154.3 mm2, the average pressure was 1.14 MPa, the force 182.13 N. After knee arthroplasty, the contact area was 119.94 mm2, the average pressure 1.522 MPa, the force 180.98 N. Following knee arthroplasty the contact area decreased significantly (P = 0.015), and the average (P = 0.0001) and maximum pressure (P = 0.0003) increased significantly. The force did not change significantly (P = 0.7642). The choice of the knee arthroplasty implant and approach to the knee joint should be considered in order to achieve an increased retropatellar contact area thus preventing smaller contact areas than before knee arthroplasty. The increased contact area could also prevent increasing retropatellar pressures after knee arthroplasty and further complications.