ASEPTIC LOOSENING OF THE FEMORAL IMPLANT AFTER CEMENTED TOTAL HIP-ARTHROPLASTY IN DOGS - 11 CASES IN 10 DOGS (1991-1995)

Objective-To determine clinical signs, radiographic findings, results of surgical management, and potential causes of aseptic loosening of t he femoral implant (ALFI) in dogs that have undergone cemented total h ip arthroplasty (THA). Design-Retrospective study. Animals-11 cases of ALFI in 10 dogs. Procedure-Medical records of all dogs undergoing THA revision surgery were reviewed. Only dogs with ALFI were included. Th e prosthesis and cement were removed by creating a longitudinal osteot omy of the cranial femoral cortex. Postoperative radiographs of all do gs that underwent THA during the study period were reviewed. Results-T he most common clinical sign was intermittent, subtle. or non-weight-b earing lameness. On radiographs obtained after THA, contact of the dis tal stem tip with cortical endosteum was evident in all dogs. Radiogra phic changes at the time of diagnosis of ALFI included asymmetric peri osteal reaction along the femoral diaphysis, radiolucent lines between the prosthesis and cement, altered implant position, and femoral frac ture. Surgical revision yielded good or excellent results in 9 cases. In 1 dog. the implant became infected; in another, aseptic loosening r ecurred. Aseptic loosening was significantly more common in dogs in wh ich there was contact between the distal stem tip and cortical endoste um than in dogs in which there was no contact. Clinical Implications-A LFI is an uncommon, but important, complication of THA, and radiograph y is warranted in dogs with clinical signs of ALFI. Initial centering of the prosthetic stem within the femoral shaft may reduce the inciden ce of ALFI.