人工股関節置換術後に大腿骨ステムの頚部折損を来した1例

Neck Fracture of an Anatomic Medullary Locking Plus Stem. Case Report

　AML(anatomic medullary locking) plusステムを用いた人工股関節置換術後15年でステム頚部に折損を来した1例を経験した．症例は79歳の男性である．自宅の庭で立ち上がろうとして右股関節痛が出現し，単純X線上，ステム頚部での折損を認めた．Extended trochanteric osteotomyを用いた再置換術を施行し，短期間ではあるが術後経過は良好である．本邦におけるAML plusステムの術後頚部折損は，本例で16例目であったが，28mm骨頭，＋6mmネックの組み合わせでは明らかに発生頻度が高くなっており，注意が必要である．

　Primary total hip arthroplasty (THA) with anatomic medullary locking (AML) stem have shown long-term success.　We report a case of neck fracture of an AML plus stem 15 years after primary THA.　A 79-year-old man suddenly experienced right hip pain while trying to stand up in a garden.　A radiography showed neck fracture at the trunnion of the stem, and a CT scan showed a retroverted cup and massive osteolysis in the acetabulum.　We performed revision THA using extended trochanteric osteotomy, and he is doing well 1 year after surgery.　Sixteen neck fracture cases of the AML plus stem have been reported in Japan, and these cases occurred most frequently when 28-mm head and ＋6-mm neck was used in combination.　We must pay particular attention when an AML plus stem with this combination is used.