The Dysplastic Hip Joint: Radiologic and Histologic Development

Abstract

The pelvic growth in dogs that developed hip dysplasia was followed radiographically, grossly, and histologically from birth to maturity to obtain clues to the earliest signs of the disease. The growth and development in the length and diameter of the pelvic bones and femurs were at a normal rate in the dysplastic dog. The bony malformations were confined to the hip joint, except for minor adjustments in shape. In the dogs described, hip dysplasia became severe. There was no recognizable evidence of the disease until the 7th week, at which time the femoral head became unstable and subluxated from the cavity of the acetabulum. In other less severe instances (mild dysplasia), the femoral head subluxation usually was not evident until the 5th–6th month of age. In even milder cases, the dogs were 12–14 months of age before hip dysplasia was apparent radiographically. The degree of the maldevelopment depended on the extent of femoral head and acetabular separation and the age of the dog when congruity was interrupted by subluxation.