CASE REPORT Veterinary Surgery 28:54-60, 1999 Osteosarcoma at the Site of Bone Infarction Associated With Total Hip Arthroplasty in a Dog DENIS J. MARCELLIN-LITTLE, DEDV, Diplomate ACVS, Diplomate ECVS, DAVID J. DEYOUNG, DVM, Diplomate ACVS, Diplomate ACVA, DONALD E. THRALL, DVM, PhD, Diplomate ACVR, and CHRISTINE L. MERRILL, DVM Objective—To report the occurrence of medullary bone infarction in both femoral canals after bilateral total hip arthroplasty (THA) and the subsequent unilateral development of an osteosarcoma at the site of bone infarction. Study Design—Clinical report. Animal Population—An 8-month-old neutered male Samoyed dog. Methods—Serial physical and radiographic examinations performed at 1, 2, 3, and 5 years after THA. Bone biopsy specimens of the right distal femoral metaphysis were taken 5 years after THA, and a complete necropsy was performed at the time of euthanasia. Results—Bilateral medullary bone infarction was visible in the femoral canals 1 year after THA and remained visible on subsequent evaluations. An osteosarcoma developed in the right distal femoral metaphysis at the site of infarction, 5 years after THA, and was found to have metastasized widely throughout the body. Conclusion—Bone infarction may occur in the femoral canal after canine THA. Clinical Relevance—Bone infarction may be a predisposing factor for the development of osteosarcoma in the femora of dogs with THAs. ©Copyright 1999 by The American College of Veterinary Surgeons S ARCOMAS OCCUR in humans in association with bone infarction 1,2 and in association with total joint prostheses. 3-13 In dogs, sarcomas have occurred in association with medullary infarction, 14-16 and the development of an osteosarcoma has been reported after a failed cemented total hip arthroplas- ty. 17 We report the case of a dog with multiple bone infarcts after bilateral uncemented total hip arthroplas- ties (THAs) and a femoral osteosarcoma that devel- oped at a site of bone infarction 5 years after surgery. Canine osteosarcoma bears a striking resemblance to osteosarcoma in humans. 18 Likewise, this case resem- bles previous reports of sarcomas in the presence of bone infarcts and joint prostheses in humans and suggests the need for close monitoring of patients with bone infarction subsequent to joint arthroplasty. CASE REPORT An 8-month-old neutered male Samoyed dog was re- ferred to the Veterinary Teaching Hospital at North Caro- lina State University for evaluation of chronic bilateral hindlimb lameness. Bilateral canine hip dysplasia was diagnosed based on radiographs and physical examination. The owners were instructed to manage the disease conser- vatively until the dog reached 1 year of age, at which time THA could be considered. The dog was reexamined 5 months later. Bilateral coxofemoral luxation secondary to hip dysplasia was diagnosed from radiographs made at that time. An uncemented total hip prosthesis (PCA Canine Total Hip System, Howmedica, Inc., Rutherford, NJ) was implanted on the right side (Fig 1). The surgery and recovery were uneventful. Four months later, the dog had normal function on the right side and severe clinical signs of From the Departments of Companion Animal and Special Species Medicine; Anatomy, Physiological Sciences, and Radiology; and Microbiology, Pathology, and Parasitology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC. Address reprint requests to Denis J. Marcellin-Little, DEDV, NCSU-CVM-CASS, 4700 Hillsborough St, Raleigh, NC 27606. ©Copyright 1999 by The American College of Veterinary Surgeons 0161-3499/99/0008$3.00/0 54