特発性脛骨内顆骨壊死の3例

Idiopathic Osteonecrosis of the Medial Tibial Plateau. Report of 3 Cases

　比較的稀な特発性脛骨内顆骨壊死の3例を経験した．全例高齢の女性で，明らかな誘因はなく安静時痛があった．MRIでLotke分類type C2例，type D1例であり，保存的治療は無効であったため，金属骨補塡材料を併用した人工膝関節置換術を行った．全例とも日本整形外科学会膝疾患治療成績判定基準(JOAスコア)の改善を認め，短期成績は良好であった．病理組織像では，軟骨下骨に骨壊死像や骨新生を認めた．MRIは早期診断に有用であると考えられた．

　We report three cases of idiopathic osteonecrosis of the tibial plateau.　All three cases were in elderly females who presented with acute knee pain at rest without any clear cause.　Radiographic examinations revealed only mild osteoarthritic changes in all three cases.　Based on the MRI images, two cases were Lotke classification type C, and the other case was type D.　Because conventional treatment was ineffective, total knee arthroplasty with metal augmentation was performed in every case.　Good short-term results were reported, and the patients' JOA scores increased.　Histological investigation revealed subchondral necrosis and bone regeneration.　We concluded that the MRI findings may be useful in making an early diagnosis of osteonecrosis of the tibial plateau in patients with no radiographic evidence of collapse.