Professor R.P. Ficat and professor J. Arlet in the late 70s devised a staging system for idiopathic bone necrosis of femoral head based on two fundamental concepts:
- a standard radiograph shows only the shadow of the mineralized portion of the bone.
- bone necrosis is the end result of severe and prolonged ischemia.
Staging
Stage 0
- pre clinical and pre radiographic
- suspected in one hip when other hip has definite disease (high incidence of bilateral involvement)
Stage I
- earliest clinical manifestation of syndrome
- sudden groin pain
- progressive, radiation to thigh, often worse at night
- pain may be aggravated by coughing
- limited hip movement
- standard AP and lateral radiographs
- usually normal, or
- show minor changes – subtle loss of clarity with poor definition or blurring of trabecular pattern; some slight patchy osteoporosis may be seen
Stage II
- extends over several months
- clinical signs persist or worsen
- changes in trabecular pattern of femoral head
- sclerosis – diffuse, localized or in a linear arc which is concave superiorly
- decalcification may be generalized or in the form of small cysts in the head, usually at some distance from the joint space
- mixed form – sclerosis and cysts may be seen
Transition phase
- crescentic line due to a subchondral fracture
- segmental flattening of femoral head resulting in ‘out of round’ appearance
Stage III
- increasing, more constant pain
- limitation of movement in all directions
- progressive functional incapacity – limp requiring use of a stick
- pathognomic appearance of sequestrum in radiograph
- break in articular margin followed by collapse of sequestrated area into femoral head
- paradoxical preserved or increased joint space in view of limited sequestrum size
Stage IV
- terminal phase of necrotic process
- progressive loss of articular cartilage
- development of acetabular osteophytes
- osteoarthritis imposed on a deformed femoral head
Two variations identified
- Ischaemic coxopathy
- narrowing of joint space in early stages of disease – generalized or confined to superomedial quadrant
- mis diagnosed as primary osteoarthritis in early stages
- seen in 6th decade
- sudden onset with pain in night
- morphologically normal as well as dysplastic hips
- Bilateral involvement
- 50% cases of idiopathic bone necrosis
- 80% of steroid associated bone necrosis
- frequently asymmetrical involvement
Read more
Ficat, R. P. “Idiopathic bone necrosis of the femoral head. Early diagnosis and treatment.”Bone & Joint Journal 67.1 (1985): 3-9.