Staging femoral head necrosis helps physicians diagnose this disease and predict the evolution of femoral head necrosis, which facilitates the selection of the most effective treatment according to the period of the lesion, individualizes treatment, and accurately assesses treatment outcome and prognosis. The following are among the many classifications that are currently widely accepted
Staging of femoral head necrosis.
I. Ficat staging method
In 1980, Ficat and Arlet proposed a four-stage classification of femoral head necrosis according to X-ray and bone function examination. This method is simple and most widely used clinically. It elaborates that the functional examination of bone is indispensable for early diagnosis, but its failure to quantify the extent of necrosis makes it impossible to judge the prognosis.
Stage I Radiographs show normal performance, but there is hip stiffness and pain with partial functional limitation of the hip joint. Hemodynamic, nuclear and histopathological examinations may be performed to confirm the diagnosis.
Stage II Radiographs show signs of bone reconstruction without changes in femoral head shape and joint space. It shows osteoporosis, osteosclerosis and cystic changes in the necrotic area. Clinical symptoms are evident and histopathological changes are definitely present on marrow core biopsy.
Stage III The continuity of the bone is disrupted on X-ray, and the top of the femoral head may be collapsed or flattened, especially at the contact with the acetabulum. The dead bone is confined to the corresponding area of compression and may be fractured and embedded, with cone-shaped subsidence. The crescentic sign is present and the joint space is normal. Clinical symptoms are aggravated.
Stage IV X-rays show further collapse of the femoral head and narrowing of the joint space, typical of osteoarthritis. The top of the socket is deformed to correspond to the flat head, and the round joint becomes oval-shaped. Clinical pain is obvious, joint dysfunction, only extension function is retained, and abduction and rotation function are completely lost.
II. Steinberg staging (University of Pennsylvania staging)
In 1995, Steinberg divided femoral head necrosis into seven stages according to the X-ray changes, bone scan examination and MRI manifestations of femoral head necrosis. This method was the first to quantify the extent of necrosis and stated that the prognosis and outcome of osteonecrosis depends mainly on the size of the lesion. It was the first to use MRI as a definitive way of staging osteonecrosis and introduced the measurement of necrotic shape and size into the staging system of osteonecrosis for the first time. However, the criteria of its staging method are too fine, which makes it less reproducible in clinical application.
Stage O Suspected osteonecrosis of the femoral head with normal or non-diagnostic radiographs, bone scans and MRI.
Stage I Normal radiographs, abnormal bone scans and/or MRI.
I-A Mild, MRI femoral head lesion less than 15% in extent.
I-B Moderate, MRI femoral head lesion range 15-30%.
I-C Severe, MRI femoral head lesion range greater than 30%
Stage II X-rays show abnormalities such as cystic and sclerotic changes in the femoral head.
II-A Mild, the extent of femoral head lesion on X-ray is less than 15%.
II-B Moderate, the extent of femoral head lesion on X-ray is 15-30%.
Ⅱ-C Severe, the extent of femoral head lesion on X-ray is greater than 30%.
Stage III subchondral fracture produces crescentic sign, which appears on X-ray as a small translucent line 1-2L below the plane of cartilage, extending to the whole extent of necrosis.
III-A Mild, subchondral collapse (crescent sign) occupies less than 15% of the articular surface.
III-B Moderate, subchondral collapse (crescent sign) occupies 15-30% of the articular surface.
Ⅲ-C Severe, subchondral collapse (crescentic sign) accounting for more than 30% of the articular surface.
Stage IV Collapse of the articular surface of the femoral head.
IV-A mild, joint surface collapse less than 15% or compression less than 2L.
Ⅳ-B moderate, joint surface collapse 15-30% or compression 2-4L.
Ⅳ-C severe, joint surface collapse1 greater than 30% or compression greater than 4L.
Stage V Narrowing of the hip joint space and/or alteration of the acetabular cartilage.
Stage VI Further degenerative changes in the femoral head and hip joint, with gradual loss of joint space and significant deformation of the joint surface.
III. ARCO staging method (international staging method)
In 1992, the International Association for the Study of Bone Microcirculation (ARCO) proposed a more systematic and comprehensive ARCO staging based on X-ray, MRI, bone scan and other examinations. This staging took into account the role of the site of femoral head necrosis in staging, and after several modifications this method was widely used in clinical studies. Many scholars believe that this is the most practical staging method and has high value for the diagnosis, treatment and prognosis of the disease.
Stage O Bone biopsy results show ischemic necrosis and other tests are normal.
Stage I bone scan is positive or MRI is positive or both. Lesions are classified as medial, central, or lateral according to location.
I-A The lesion extent is less than 15% of the femoral head.
I-B The extent of the lesion is 15-30% of the femoral head.
I-C The lesion extent is greater than 30% of the femoral head.
Stage II X-ray abnormalities: speckled manifestation of femoral head, osteosclerosis, cystic changes, bone sparing. no collapse of femoral head on X-ray and CT scan, positive bone scan and MRI, no changes in acetabulum. The lesions were classified as medial, central, and lateral according to the site.
II-A lesion extent was less than 15% of the femoral head.
II-B The extent of the lesion is 15-30% of the femoral head.
II-C The lesion extent is greater than 30% of the femoral head.
Stage III Crescentic sign is seen on X-ray. The lesions are classified as medial, central and lateral according to the location.
III-A The extent of the lesion is less than 15% of the femoral head or the femoral head collapses less than 2L.
Ⅲ-B The extent of the lesion is 15-30% of the femoral head or the femoral head is collapsed 2-4L.
III-C Lesion extent greater than 30% of the femoral head or femoral head collapse greater than 4L.
Stage IV Flattening of the articular surface of the femoral head, narrowing of the joint space, sclerosis of the acetabular bone, cystic changes and formation of marginal bone redundancy are seen on X-ray.
IV. Four-stage and six-stage method
The four-stage and six-type staging method was proposed by Zhao Dewei on the basis of Ficat staging, combined with functional examination and clinical manifestations. This staging method focuses more on clinical manifestations, but is of little value in guiding treatment.
In stage I, there is only transient joint stiffness and pain, usually accompanied by some limitation of joint movement, and the symptoms are relieved after rest. No positive findings are seen on X-ray, and occasionally uniform or speckled osteoporotic areas may be seen.
Stage II weight holding and hip pain occurs with prolonged standing. There are signs of bone reconstruction on X-ray, but there is no change in the shape of the femoral head or joint space. This stage is further divided into two subtypes, A and B.
IIA Mild restriction of hip joint movement. Bone sparing is diffuse, with obvious reconstructive images that may involve the acetabulum. The entire center of the femoral head shows a uniform and consistent osteosclerotic zone with relatively clear demarcation. It is surrounded by punctate and lamellar areas of hypodensity and isolated cystic changes.
The crescent sign (a sign of separation or collapse of the subchondral bone trabeculae from the cartilage) can occasionally be seen. The presence of crescentic sign is a prodromal sign of trabecular necrosis.
In stage III, hip pain persists, is mild, and is not significantly relieved by rest. x-rays show a break in the continuity of the subchondral trabeculae, with obvious capsular changes, often surrounded by a sclerotic rim, and a flattening of the femoral head due to subchondral fracture in the weight-bearing area. The joint space is normal or slightly narrowed because the overlying cartilage remains normal.
Stage IV subchondral osteonecrosis is progressively enlarged and shows narrowing of the joint space and typical osteoarthritic changes. This stage can also be divided into two subtypes.
ⅣA further flattening and compression of the femoral head, collapse of both the inner and outer sides of the head, narrowing of the joint space, and small bony and cystic changes visible below the subchondral bone of the head and in the weight-bearing part of the acetabulum, which are signs of osteoarthritis of the hip joint.
IVB Further compression and destruction of the femoral head and acetabulum with degenerative changes in the joint make necrosis and arthritis no longer clearly distinguishable. To accommodate the flattened deformity of the femoral head, the acetabular roof also changes, from a spheroid joint to a cylindrical joint, with fragmentation and fracture of some of the femoral head visible. Although a greater range of flexion is preserved, it leads to a total loss of abduction and rotation, i.e., signs of subluxation.
Early stage femoral head necrosis
The current international staging method often used stipulates the concept of early diagnosis of femoral head necrosis as stage 0-2. Stage 0 diagnosis relies on bone biopsy; stage 1 diagnosis relies on bone scan or magnetic resonance imaging (MRI); stage 2 diagnosis relies on CT, and high quality radiographs can also make the diagnosis. Only on the basis of early diagnosis can treatment to preserve the femoral head be performed.