人工膝関節全置換術後の膝蓋骨の高さが術後屈曲角に及ぼす影響

Influence of Postoperative Patellar Height on Knee Flexion after Total Knee Arthroplasty

　人工膝関節全置換術(以下，TKA)の術後膝蓋骨の高さと膝屈曲角との関係を検討したので報告した．本研究では膝蓋骨の高さをjoint lineからの距離とし，計測肢位を最大屈曲位とした．術後4週目の屈曲角が術後1年でも保たれていたが，膝蓋骨の高さは，術後1年まで徐々に低下していた．膝蓋骨の高さが5mm以上低下した症例では，膝蓋骨の高さの変化量と屈曲角の変化量との間には特に強い相関を示した．可動域低下の原因の1つに膝蓋骨の高さの低下が考えられるので，低下を防ぐ術式や術後リハビリテーションの工夫が求められる．

　We investigated the relationship between postoperative patellar height, defined as the distance between the inferior edge of the patella and the superior surface of tibial polyethylene, and the flexion angle of the knee after TKA.　The flexion angle after TKA was maintained for a year, but patellar height decreased gradually over the year.　In the cases in which patellar height decreased by more than 5 mm, there was a positive correlation between the decrease in patellar height and the decrease in flexion angle.　Now that the decrease in patella height (patella baja) is known to be capable of decreasing the knee flexion angle, modifications of operative technique and rehabilitation are needed to prevent patella baja.