セメントレス人工膝関節置換術後早期に脛骨コンポーネント周辺で発生するradiolucent lineに対する検討

Assessment of Early Postoperative Radiolucent Line around the Tibial Component after Cementless Total Knee Arthroplasty

　セメントレス脛骨コンポーネント周辺でimplant micromotionにより術後早期に発生するradiolucent line（RLL）ついて検討した．RLLはすべて術後6カ月以内に出現したが3mmを超える症例はなく，経過観察期間中すべて非進行性であった．またHSS scoreによる検討結果，RLL出現膝群と非出現膝群間で臨床成績に有意差はなかった．一方，使用機種でみたとき，ScorpioのRLL出現率はAdvanceより有意に低かったが，これはScorpioがハイドロキシアパタイトコーティングされているためと考えられた．

　Because of implant micromotion an early postoperative radiolucent line (RLL) sometimes appears around the tibial component after cementless total knee arthroplasty. We examined 67 knees for an RLL after treatment with 2 different implants (Scorpio implant in 36 knees；Advance implant in 31 knees). An RLL was detected in 20 of the 67 knees, and all of them appeared within 6 months postoperatively. None of the RLLs exceeded 3 mm in length, and none expanded during the follow-up period. The rate of improvement in the HSS score in the 20 knees with an RLL was not significantly different from the rate in the 47 knees without an RLL at any time measured. The incidence of RLLs in Scorpio implant group (3 out of 36 knees) was significantly lower than in the Advance implant group (17 of 31 knees). We concluded that the development of an RLL does not affect the clinical outcome. The significantly lower incidence of RLLs in the Scorpio implant group was probably related to its hydroxyapatite coating of the implants.