Clinical history A nine month old male Jack Russell terrier presented with chronic progressive lameness in both pelvic limbs. A ventrodorsal radiograph was made of the pelvis with the hind limbs in extension. VD pelvis Enlargement Radiograph changes Changes affect both hip joints
- Pattern of osteolytic and osteoblastic areas within the femoral heads
- Modeling of the femoral heads with flattening most obvious on the right
- Uneven thickening of the femoral necks with increased density extending distally to the trochanteric region
- Femoral heads seat loosely within the acetabulae
- Acetabular cups are modeled with uneven density of the subchondral bone
- Soft tissue atrophy
- Growth plates of the capital epiphyses are flattened
Diagnosis Aseptic necrosis of the femoral heads (Legg Calve Perthes disease). Comments Radiographic changes are primarily in the femoral epiphyses and are a combination of bone lysis and bone production creating the pattern of mixed density seen radiographically. Changes in the acetabula occur later since they represent secondary modeling that is the result of the loss in bone density in the femoral epiphyses. Notice that the radiolucent areas in the left femoral head tend to join together and will soon permit fragmentation of a portion of the femoral head. Note the increase in density within the metaphyses. This may be the earliest radiographic pattern to be seen in aseptic necrosis of the femoral head reflecting the early change in pattern of weight bearing.
