I. Onset
Femoral head necrosis is a disease that scares patients and causes headaches for doctors. The former is mainly caused by femoral neck fracture, acetabular fracture and hip dislocation, while the latter is mainly caused by the application of corticosteroids and heavy alcohol consumption in China. Non-traumatic femoral head necrosis mainly affects young adults aged 20=50 years old, and about 80% of patients have bilateral onset.
Studies of the natural history of the disease have shown that without effective treatment approximately 80% of cases of osteonecrosis develop femoral head collapse within 0.5 to 3 years. Once the femoral head collapses (positive crescent sign), 87% of the hips will progress to the point of requiring artificial joints within 24 months, thus causing great harm to the family and society. The long-term efficacy of artificial joint replacement in young and middle-aged people is still difficult to predict, so it is very important to preserve the patient’s own joints as much as possible, and early diagnosis and scientific treatment are the keys to improve the efficacy of joint preservation treatment.
Risk factors and clinical manifestations of femoral head necrosis
About 70% of patients with osteonecrosis of the femoral head have clear causative factors, including: history of hormone use, history of long-term heavy alcohol consumption, history of trauma to the hip or the rest of the body (such as cranial and spinal), history of immune connective tissue disease, the rest of the body or the opposite side has been diagnosed with osteonecrosis, etc. If osteonecrosis has been diagnosed on one side, the possibility of osteonecrosis on the opposite side is 50%-80%. Other factors associated with femoral head necrosis are hematologic disorders, Gaucher’s disease, decompression sickness, chronic pancreatitis, chronic kidney disease, diabetes, toxic shock and endotoxic reaction. People with these causative factors are at high risk for osteonecrosis. If hip discomfort occurs in this group, one should think of osteonecrosis of the femoral head.
Most patients only occasionally feel soreness and discomfort around the hip and thigh to the top of the knee joint, and the symptoms worsen when walking long distances or carrying weight for a long time, and limp appears, but it can be relieved after rest. Some patients develop nocturnal pain, which is a typical manifestation of ischemia.
Because the symptoms are not heavy and there is no specificity, it is easy to be ignored by patients and doctors and delay the disease. In outpatient clinics, it is common to see patients who are first diagnosed with more severe femoral head necrosis, and some even have collapsed and deformed femoral head. In the early stage of femoral head necrosis, there are often no obvious abnormal signs during physical examination, but hip pain is often induced by strong internal rotation or abduction of the lower limbs.
Imaging examination
1.X-ray examination: X-ray examination of early femoral head necrosis generally has no obvious abnormality, but in high quality X-ray film sometimes can be seen in the femoral head bone trabeculae streaks unclear, there are speckled high-density and/or low-density intermingled lesions, slightly later lesions will appear to be high-density foci of low-density lesions wrapped by high-density demarcation lines. In more advanced lesions, subchondral bone resorption and CrescentSign may be seen. CrescentSign indicates the loss of subchondral bone resorption, loss of cartilage support, and, without effective treatment, rapid head collapse and flattening. The crescent sign can therefore be regarded as the dividing line between early and late stage femoral head necrosis.
2, radionuclide bone scan and single photon emission computed tomography (SPECT) bone scan: is a very sensitive and less specific important screening test, because it reflects the changes in the level of cellular metabolism at the lesion site, so in the early stage of the disease (the first few days after the appearance of symptoms) can show abnormal signals, and at this time the X-ray examination is often negative. Therefore, it is important for the early diagnosis and screening of osteonecrosis.
In the early stage of osteonecrosis, the focal area is ischemic and the bone scan shows a low resorptive signal, then, due to the inflammatory response of the surrounding normal tissue caused by necrotic tissue and capillary proliferation, a ring of high resorptive signal appears at the edge of the low resorptive signal lesion. This has been described as “Coldin Hot”. This is the characteristic bone scan performance of osteonecrosis, that is, the appearance of this bone scan signal can be diagnosed femoral head necrosis.
MRI can show the lesion area at the early stage of the disease, when ischemia causes cell metabolism disorder, resulting in edema and degeneration of cells and tissues, therefore, its sensitivity is no less than that of bone scan.
In early stage femoral head necrosis, a low density line is visible on the T1 image of MRI film, which is actually the demarcation line between normal bone and necrotic bone. This high-density line is actually a proliferative granulation tissue band, which is low signal on T1 image and high signal on T2 image because of its high water content. MRI can also show the location and extent of the lesion, which can provide a basis for selecting a treatment method and determining the treatment plan. At the same time, it can be used to evaluate the effect of a certain treatment method because it can show the subtle changes in the bone.
Four, femoral head necrosis diagnostic criteria
1.Montand Hungerford criteria
(1) Specific indicators
(1) Collapse of the femoral head.
(2) subchondral bone hypodensity line (crescent sign).
(3) Presence of dead bone on the anteromedial aspect of the femoral head.
(4) Bone scan showing a hypodense shadow surrounded by a high-density shadow, i.e., hot with cold.
(5) The presence of a double line sign on the T2 image of MRI.
(6) Bone biopsy shows regional trabecular necrosis and vacuity of the osteoclastic crypt.
(2) Non-specific indices
(1) Collapse of the femoral head with joint space narrowing.
(2) Speckled hypodense shadow or high-density shadow in the femoral head.
(3) Bone scan showing high resorption signal.
(4) MRI examination showing bone marrow edema or fibrotic signal.
(5) Painful hip joint movement and no abnormalities on X-ray.
(6) A history of chronic excessive alcohol consumption or hormone use.
(7) Bone biopsy shows non-specific lesions suggesting bone marrow edema or fibrosis.
2.Main signs
(1) Radiological examination
(1) Collapse of the femoral head.
(ii) Sclerotic zone (demarcation line) within the femoral head.
(iii) subchondral crescent sign of the femoral head, no joint space narrowing, no acetabular deformation.
(2) Laboratory tests
(1) Positive radionuclide bone scan (ColdinHot).
(2) Marrow core biopsy confirmed osteonecrosis.
3.Secondary signs
(1) Radiological examination
① collapse of the femoral head with narrowing of the joint space.
(ii) Cystic lesions or mixed low-density and high-density lesions in the femoral head.
(3) Flattening of the weight-bearing surface of the femoral head.
(2) Laboratory tests
(1) Hot or cold areas on bone scan.
(ii) Hypodense areas seen on MRI.
(3) Clinical signs
① pain in the hip or thigh when walking or standing.
②History of hormone therapy or long-term alcohol consumption.
4.ANFH diagnosis: 2 or more major signs of 2 or more lengths.
5.Probable ANFH: one major sign or more than 4 minor signs (at least one radiological sign).
6.Exclude tumor or inflammatory lesion.
V. Staging method of femoral head necrosis
In 1973, Marcus firstly proposed the imaging staging method of femoral head necrosis according to the changing pattern of the disease, from light to kind. Based on this, a variety of modifications were later introduced, and the three most used methods are Ficat staging, Steinberg staging and ARCO staging, the purpose of which is to help choose the appropriate treatment.
Ficat staging
1. stage 0 with no pain, normal plain films and abnormalities on bone scan and MRI.
2, Stage I with pain, normal plain films and abnormal bone scans with MRI.
3. stage IIa (excessive stage) with pain, cystic degeneration or/and sclerosis seen on plain film, abnormal bone scan and MRI, and no subchondral fracture.
4. stage III with pain, collapse of the femoral head seen on plain film, abnormalities seen on bone scan and MRI, crescentic sign (subchondral collapse) or/and step-like collapse of subchondral bone.
5. Stage IV with pain, acetabular lesions on plain film, joint space narrowing and osteoarthritis, and abnormal bone scan and MRI.