The Journal of Arthroplasty Vol. 11 No. 5 1996 Case Report Periprosthetic Metastatic Carcinoma Pitfalls in the Management of Two Cases Initially Diagnosed as Osteolysis Andrew H. Schmidt, MD,* Gordon Walker, MD,~- Richard F. Kyle, MD,* and Roby C. Thompson, Jr, MD t Abstract: Periprosthetic osteolysis is a well-described phenomenon associated with total hip arthroplasty. Two cases are presented in which apparently healthy patients developed lyric lesions adjacent to cementless hip implants. Despite atypical features, the lesions were initially attributed to wear debris-induced osteolysis, and it was dis- covered during revision surgery that metastatic tumor was present. For one patient, if the initial diagnosis had been correct, subsequent surgery and related complica- tions may have been avoided. It is important to consider the entire differential of radiolucent bone lesions whenever a patient presents with periprosthetic osteolysis. If revision surgery is not warranted on the basis of loosening, then a thorough medi- cal examination, close follow-up evaluation, and/or biopsy should be performed to rule out metastatic disease. Key words: total hip arthroplasty, osteolysis, metastatic carcinoma, adenocarcinoma, clear cell carcinoma. In general, osteolysis may be the harbinger of infectious, neoplastic, or metabolic bone disease; however, when associated with total joint prosthe- ses, progressive endosteolysis is considered to be an inflammatory tissue response to particulate wear debris, mediated by macrophage-induced osteoclastic bone resorption [1,2]. Periprosthetic lucencies were first reported in association with infected cemented total hip pros- theses [3]. Subsequently, this phenomenon was observed in aseptic loosening of cemented devices, and came to be known as cement disease [4,5]. Periprosthetic osteolysis has now been described in relation to both stable and loose, cemented or unce- mented total hip prostheses [4,6-11]. Osteolysis has From ~Hennepin County Medical Center and fUniversity of Min- nesota, Minneapolis, Minnesota. Reprint requests: Andrew H. Schmidt, MD, Department of Orthopedic Surgery, Hennepin County Medical Center, 701 Park Avenue, Minneapolis, MN 55415-1829. 613 become the most common complication of unce- mented total hip arthroplasty (THA) and is seen with increasing frequency as longer follow-up eval- uation of these devices is accrued [7]. Periprosthetic osteolysis has become so well recognized, and its presentation so stereotyped, that the clinician may fail to consider that the differential diagnosis of an osteolytic lesion remains broad. The purpose of this report is to highlight the pitfalls in the management of periprosthetic bone lesions by illustrating two cases in which the osteolytic lesion was ultimately proven to represent metastatic carcinoma. Case Reports Case I A healthy 50-year-old woman underwent bilat- eral THA in July 1992 for severe osteoarthritis. The patient reported immediate and complete