Presentation
Right hip pain. No fever or trauma.
Patient Data
Subchondral lucency with sclerosis in the right femoral head. There is mild flattening of the articular surface. Equivocal/subtle change in the left femoral head.
Progression of right femoral head findings with enlarging subchondral lucency and sclerosis, severe articular surface collapse and secondary osteoarthritic change. The left femoral head shows subchondral change but the articular surface is preserved.
Right hip arthroplasty with the progression of left hip subchondral changes and mid left articular surface collapse.
Case Discussion
The pathognomonic findings on sequential xrays and history led to a diagnosis of bilateral AVN (avascular necroses) of the hips, with the right side being affected first.
AVN is necrosis of cellular elements of the bone secondary to ischemia. Potential causes of interrupted blood supply include trauma, steroids, alcoholism, sickle cell disease, radiation, Gaucher's disease and Caisson's disease.
The femoral head, and in particular its anterolateral weight bearing part, is most vulnerable to AVN. Patients may be asymptomatic or there may be acute or chronic pain in the affected hip.
The natural history is that of necrotic bone resorption and healing attempt with sclerosis, which may lead to articular surface collapse and secondary osteoarthritis.
Early radiographic findings are patchy subchondral lucency and sclerosis due to necrotic bone resorption and healing attempt. This leads to structural weakness, subchondral 'crescent fracture', articular surface collapse and subsequent changes of secondary osteoarthritis.
Differentials include insufficiency fracture of the femoral head.
40% of cases are bilateral with the other hip showing radiographic changes in 3-4 years (as in this case).
MRI is more sensitive than radiographs in early disease and shows the typical subchondral focus limited by a 'double-line ' on fluid sensitive images. Articular surface collapse is best seen on sagittal images or radiographs.
Treatment options before collapse and osteoarthritis include core decompression(with bone graft) and rotational osteotomy to alter weight bearing. After collapse without osteoarthritis, hemiarthrolplasty and after osteoarthritis, total hip replacement are options.