RESUMO
CASE DESCRIPTION: A 15-month-old 6.5-kg (14.3-lb) castrated male mixed-breed dog was evaluated because of a 4-month history of progressive intermittent non-weight-bearing lameness of the left pelvic limb. CLINICAL FINDINGS: Orthogonal radiography of the hip joints revealed a 4-mm atypical radiolucent lesion on the distal caudomedial aspect of the left femoral head and a disproportionately large-diameter femoral medullary canal with a low canal flare index. Prolonged unresponsiveness to medical management and progressive enlargement of the lesion prompted the recommendation for total hip replacement (THR). TREATMENT AND OUTCOME: THR was performed to restore pain-free function of the left pelvic limb and normal activity. A circular osteochondral flap was grossly evident on the femoral head. Histopathologic findings for this portion of the bone indicated an arteriopathy-induced focal subchondral osteonecrosis that had resulted in articular surface collapse. The noted idiopathic arteriopathy had disrupted the normal blood supply to the affected area. On reexamination and radiographic evaluation 13 months after THR, the dog appeared to have pain-free function of the affected limb and had returned to normal activity with no reported complications or problems. CLINICAL RELEVANCE: To the authors' knowledge, this report represented the first description of arteriopathy-induced focal osteonecrosis of the caudomedial aspect of the femoral head and its successful treatment in a young dog. This type of lesion may more commonly be the cause of hip joint osteoarthritis in young dogs than previously recognized because establishing a definitive diagnosis requires early recognition and histologic evaluation before advanced degenerative changes develop that obscure the underlying etiology.
