Periprosthetic malignancy causing failure of total hip arthroplasty is a rare entity. Metastasis of malignant tumour to the proximity of orthopaedic implants is even more uncommon. We present a case of a 74-year-old female with an infected Austin Moore prosthesis, requiring a two-stage revision total hip arthroplasty. Within 2 years postoperatively, erosion of the lesser trochanter was noted. Further revision surgery was performed with the insertion of a cement spacer. Despite the expectation of an infected prosthesis, intraoperative frozen section showed sarcoma and the final pathology was metastasis of a recurrent gastrointestinal stromal tumour (GIST). Metastatic GIST to total hip prosthesis had not been reported previously and this case illustrates how intraoperative frozen section can aid diagnosis and management. We also highlighted some diagnostic clues, differentiating this rare diagnosis from septic loosening and osteolysis. Malignant infiltration should be considered as a differential diagnosis in failed total hip arthroplasty, especially in patients with a previous history of malignancy.
惡性腫瘤造成全關節置換失敗的罕見的。惡性腫瘤轉移到骨科義體鄰近的病例更是稀有。我們提出一個病例，關於一名74歲的婦女，在Austin Moore義體受感染的情況下，需要進行兩個階段全髖關節翻修置換術。術後2年以內，小粗隆受到侵蝕，需要進一步進行翻修手術，插入水泥隔板。本來預計義體受感染，但術中冰凍切片顯示肉瘤，最終病理為的一個複發性的胃腸道間質腫瘤（GIST）轉移。GIST轉移到全髖關節義體沒有曾被報導。這病例說明了術中冰凍切片如何可以幫助診斷和治療。我們強調了一些診斷線索，將這種罕見的診斷與假體周圍感染和骨溶解區分。惡性腫瘤侵蝕，尤其是在有惡性腫瘤病史的患者，應被視為在全髖關節置換術失敗的鑑別診斷.
