Femoral osteonecrosis is recognized as a medical stubborn disease in the world, and the disability rate is almost 100%. With the accelerated pace of life, the incidence of osteonecrosis increases year by year, such as hormones (including food and drug hormones), trauma, alcohol consumption, rheumatism, osteoporosis, osteoarthrosis, hyperlipidemia, etc. can lead to ischemic necrosis of the femoral head.
The treatment effect of femoral head necrosis has a great relationship with the severity of the disease, the early and late detection, and the stage of the disease, the earlier the lesion is found, the lighter the disease, the better the treatment effect, therefore, femoral head necrosis should be diagnosed early and early treatment, early diagnosis and prediction of whether the diseased femoral head will collapse, non-surgical treatment for those who will not progress can greatly save medical costs and reduce patient pain.
A. What tests should be done in the early stage of suspected femoral head necrosis?
1. What imaging examinations should be done in the early stage of suspected femoral head necrosis? How to carry out imaging examination scientifically? When the patient has hip pain and osteonecrosis susceptibility factors, suspected femoral head necrosis, should choose MRI or isotope bone scan examination, can be early detection of osteonecrosis.
2, When diagnosing or understanding the progress of femoral head necrosis, imaging examinations should be selected scientifically. Isotope bone scan can be used for screening of osteonecrosis of femoral head; MRI is the best means for early detection of osteonecrosis; once the manifestation of osteonecrosis appears in X-ray or CT, osteonecrosis of femoral head has progressed to at least stage II, through them to understand the progress of osteonecrosis of femoral head.
Second, the application of MRI in the diagnosis and treatment of osteonecrosis
Magnetic resonance imaging (MRI) is the gold standard for the diagnosis of osteonecrosis of the femoral head. Osteonecrosis has its specific manifestation in MRI images. When necrosis occurs in the outer superior region of the femoral head, bone repair begins at the interface between the necrotic area and normal bone, and new bone tissue is formed to cover the necrosis, thus producing a sclerotic rim. The abnormal signal characteristic of femoral head necrosis in T1 and T2-weighted phase is surrounded by a low signal band, which represents the aforementioned sclerotic rim. If this “linear sign” is present, the diagnosis of osteonecrosis can be established. As the repair process continues, a band of fibrous granulation tissue is formed on the medial side of the sclerotic margin, which appears as a high signal in the T2-weighted phase, and this “double line sign” is a characteristic MRI manifestation of osteonecrosis. MRI should be used to detect the presence of osteonecrosis, except in patients with unilateral osteonecrosis to determine whether necrosis is occurring on the other side, and it is wrong to review MRI to understand the progress of the disease during the follow-up.
CT examination in the application of osteonecrosis diagnosis and treatment
CT examination is mostly used to understand the progress of osteonecrosis, and help to choose the appropriate treatment according to its imaging performance.The imaging performance of CT examination is the disappearance of trabeculae, sclerosis, cystic change and collapse in the necrotic area, and the appearance of sclerotic zone around the necrotic area, and the “asterisk sign” is the performance of bone lamellar repair in the trabecular structure. The dotted low signal area or microfracture within the necrotic area indicates early collapse of the femoral head, and the osteonecrosis has progressed to stage III.
The application of plain X-ray in the diagnosis and treatment of osteonecrosis
Like CT examination, plain X-ray is used to understand the progression of osteonecrosis. Once the manifestation of osteonecrosis appears on the X-ray film, it means that it has progressed to stage II. If the “crescent sign” appears, it is a sign of subchondral plate fracture and early collapse of the femoral head, indicating that it has progressed to stage III. When taking X-rays, the orthopantomogram of the pelvis and the froggy phase of both hips should be included, because only the froggy phase can detect the collapse of the femoral head in front of the necrosis.
V. When to do X and CT examination
After the diagnosis of femoral head necrosis is confirmed by MRI examination, X-rays and CT examination should be done. In the follow-up of the disease, those who have the condition should review the X-ray and CT examination every 3 months within 2 years.
Six, bone scan examination in the diagnosis and treatment of osteonecrosis
Bone scan is highly sensitive for early detection of osteonecrosis, but still lacks specificity for the diagnosis of osteonecrosis. Bone scan is suitable for patients suspected of multifocal osteonecrosis but failed to do MRI examination, or patients at high risk of osteonecrosis with persistent pain in the hip but no abnormality is seen in MRI. The characteristic sign of bone scintigraphy for the diagnosis of osteonecrosis is when the cold area in the hot area, i.e., the “fried bagel” sign, is manifested.
Seven, the advantages and disadvantages of bone scan
Advantages: high sensitivity; disadvantages: poor specificity.
Eight, imaging diagnostic criteria
Strictly speaking, the diagnosis of osteonecrosis requires pathological diagnosis, but in the clinical application is limited. MRI images can be seen as “linear sign” or “double line sign”, and the osteonecrosis lesion in the lipid suppression phase is high signal.
The prediction and significance of imaging on femoral head collapse
According to the study of the natural course of femoral head necrosis, about 80% of patients with untreated femoral head necrosis will experience collapse of the joint surface of the femoral head within 1 to 3 years. Since non-traumatic osteonecrosis occurs mostly in middle-aged and young adults, the long-term outcome of artificial hip arthroplasty in these patients is still uncertain, so it is necessary to seek effective treatment to preserve the femoral head. Not all cases of osteonecrosis progress to collapse of the femoral head, and early diagnosis and prediction of whether the affected femoral head will collapse and non-operative treatment of those that do not progress can result in significant savings in medical costs and reduced patient suffering. The MRI data of femoral head necrosis is input into the computer, and the software system is used to perform 3D reconstruction to determine the site of necrosis in three dimensions and accurately calculate the volume of osteonecrosis, predict whether the femoral head will collapse, and individualize the simulation of hip joint load computer finite element analysis to determine whether the femoral head will collapse in the future.