GREGORY S. MARSOLAIS, DVM, MS, Diplomate ACVS 1,2,3 , JEFFREY N. PECK, DVM, Diplomate ACVS 1,2,3 , CLIFFORD BERRY, DVM, Diplomate ACVR 1,2,3 , and ANN JOHNSON, DVM, MS, Diplomate ACVS 1,2,3 1 Monterey Peninsula Veterinary Surgical Service, Carmel, CA ; 2 Affiliated Veterinary Specialists, Maitland, FL and Central Florida Veterinary Radiology, Maitland, FL; and 3 Department of Veterinary Medicine, College of Veterinary Medicine, Universit Vet Surg 2009 August 38 6 677-680 ABSTRACT Objective—To document the prevalence of femoral medullary infarction associated with the Zurich Cementless Total Hip Replacement (ZCTHR) system in dogs. Study Design—Case series. Animals—Dogs (n=35) with 41 ZCTHR implants. Methods—Medical records (February 1999–December 2002) were reviewed for dogs that had ZCTHR and at least 1 year follow-up with radiographic evaluation. Thirty-five dogs (41 ZCTHR) met the inclusion criteria. Femoral morphologic data, implant to bone relationships, and medullary infarcts were recorded. Data were analyzed for associations between infarct occurrence and morphologic details and dog characteristics. Results—Eight of 41 femurs had radiographic evidence of infarcts (19.5%). Dogs with infarcts were significantly younger (mean [±SD] age, 18.5±5.2 months) compared with those without infarction (mean age, 44.4±5.6months; P=.027). None of the other variables were significantly different between dogs with and without infarcts. Three femurs with infarcts ultimately developed stem loosening. Conclusion—A higher prevalence of femoral medullary infarcts was identified with ZCTHR compared with incidence reported for other total hip systems. Younger dogs were more likely to develop infarction. Clinical Relevance—Femoral infarction appears to be associated with stem loosening. Adjustments in surgical technique or delaying surgery beyond 18 months of age may reduce incidence of infarction but needs further evaluation.