Legg-Calvé-Perthes disease (femoral avascular necrosis) is a multifactorial genetic disease of small-breed dogs characterized by osteonecrosis of the proximal femoral epiphysis and secondary osteoarthritis.
This disease occurs almost exclusively in toy- and miniature-breed dogs.
The cause of this disease is unknown, but various theories have been promulgated such as genetic predisposition, osteomyelitis, trauma and metabolic and hormonal imbalances. However, vascular abnormalities seems likely as small toy-breed dogs have particularly narrow vascular channels through which the superior retinacular vessels reach the epiphyseal plates, and repeated trauma may well induced subclinical synovitis resulting in perfusion disturbances within the epiphysis.
As the disease progresses, there is mechanical collapse, asymmetric growth, and disturbed enchondral ossification at the growth plate, leading to degenerative changes that can be visualized radiographically.
Clinical signs usually manifest as an intermittent unilateral hindlimb lameness which presents at 4 - 6 months of age or older and progressively worsens over time. Recent trauma may be evident, and the affected leg may show signs of muscle atrophy due to disuse. Males and females are equally affected and bilateral involvement occurs in only 12% to 16% of cases.
Diagnosis is usually based on confirmatory changes to the femoral head, characterized by degenerative joint disease, bone lysis, osteoarthritis and osteophyte formation.
Treatment in most cases requires excisional arthroplasty (removal of the femoral head), which is often curative of clinical signs.
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