Curriculum · Musculoskeletal / Orthopedic / Rheumatology
Avascular necrosis of the femoral head in a child
What it is
Perthes disease is a degenerative condition affecting the hip joints of children, and it is avascular necrosis of the femoral head. Legg-Calvé-Perthes disease is avascular necrosis of the proximal femoral head resulting from compromise of the tenuous blood supply to this area. The age is 4-8 years.
How it presents
Hip pain develops progressively over a few weeks, with a limp, stiffness and reduced range of hip movement.
How it is diagnosed
On x-ray the early changes are widening of the joint space, and the later changes are decreased femoral head size and flattening. X-ray detects only late changes, so MRI is what detects early changes: when hip pain persists for 6 months and the x-ray shows a normal hip joint, MRI is the next step, and it shows the area of necrosis of the femoral head with the acute edema that indicates AVN. Sickle cell disease is one setting in which this happens. Once the necrosis affects the cartilage the joint changes from a normal congruent joint to abnormal non-smooth joint surfaces.