However, it is difficult to avoid the collapse of the necrotic femoral head and the occurrence of osteoarthritis, and the chance of preserving the femoral head is lost, so the only treatment available is joint replacement. Currently, according to the staging (e.g. Ficat and ARCO staging), only in the early stage (pre-collapse of the femoral head) is there a chance to save the femoral head from collapse. Therefore, early detection and diagnosis of femoral head necrosis is of great importance for treatment and prognosis.
I. Clinical characteristics.
Femoral head necrosis is generally insidious in its onset, and there are often no obvious clinical symptoms in the early stage. Pain is the most common clinical manifestation. Mostly manifested as pain in the groin area, radiating to the front or inner side of the thigh. This pain can be sudden and intense, but it is mostly a non-severe hip pain that gradually worsens.
A careful history should be taken of the patient with hip pain. This includes history of hormone use, history of alcohol consumption, and history of trauma. Some rare causes of femoral head necrosis, such as decompression sickness and hemoglobinopathy, should also be considered.
The use of glucocorticoids is one of the most important causes of ischemic necrosis of the femoral head. The relationship between the time of onset of ischemic necrosis of the femoral head and the duration and dose of hormone use is not clear and can vary from a few months to several years, so it is important to ask the patient carefully about his or her history of hormone use. Sometimes the patient may not be aware that hormones have been used, so patients who have been treated with medications at unregulated facilities should be suspected of having used hormones.
Long-term heavy alcohol consumption is another common cause of femoral head necrosis, mostly in adult male patients, but the sensitivity to alcohol varies greatly from person to person, so the amount and duration of alcohol consumption varies greatly from patient to patient.
Other systemic diseases such as decompression sickness, hemoglobinopathy and LCPD can also lead to femoral head necrosis. Patients with all of the above diseases belong to a high-risk group for developing femoral head necrosis and should be advised to pay attention to hip symptoms and have regular checkups so as not to delay the condition and miss the best time for treatment.
For patients complaining of hip pain or lower limb pain, careful examination is very important. First of all, the source of pain should be clarified, except for lumbar spine disorders, knee disorders and intra-abdominal disorders. Therefore, the physical examination should be comprehensive and not only the hip joint examination. The typical signs of early stage femoral head necrosis are limited hip movement, such as limited abduction and external rotation, limited flexion and internal rotation, and the most important positive signs are positive 4-character test and pain during excessive rotation. Sometimes there is pressure pain in the groin area.
If a patient complains of hip pain, asks for a history of the presence of predisposing factors, and physical examination reveals restricted hip movement, the presence of the disease should be highly suspected and the appropriate tests should be performed. The examination for early diagnosis of femoral head necrosis is mainly imaging examination, including X-ray, CT, MRI, bone scan, angiography, etc.
Second, X-ray examination.
X-ray is not an effective means of early diagnosis of femoral head necrosis, but it is economical and easy, and is an important means of checking femoral head necrosis, and has an irreplaceable role in observing the progress of the disease and the selection of treatment methods. In order to improve the diagnosis rate, both orthopantomogram and frog position films should be taken, and lower limb traction X-ray films can also be used to form negative pressure in the subchondral bone separation area, so that the “crescent sign” can be more clearly seen. The typical X-ray manifestation of femoral head necrosis is the “crescent sign”, which is the manifestation of femoral head collapse, and the development of the patient’s condition is usually inevitable at this time. Early X-rays of femoral head necrosis show changes in the density of the femoral head, with increased bone density in the weight-bearing area of the femoral head, surrounded by lamellar hypodensity shadows, which is a manifestation of creeping replacement in the process of necrosis repair; abnormal arrangement of bone trabeculae, such as blurring or even disappearance of the normal bone trabeculae tension and pressure lines. In late stage, cystic degeneration, sclerotic area, destruction of bone trabecular structure, change of femoral head shape, collapse, formation of bone redundancy on the joint surface, and narrowing of gap, etc. appear.
III. Computed X-ray tomography (CT).
CT, especially high-resolution CT, is superior to X-rays in diagnosing femoral head necrosis, and can more clearly show the occurrence site and lesion scope of femoral head necrosis, and can accurately show small-scale trabecular changes, and has unique advantages for early detection of subchondral bone collapse, which is one of the important tools for diagnosing femoral head necrosis. However, because CT is still an X-ray image, its early diagnosis of femoral head necrosis is limited. The important manifestation of early femoral head necrosis on CT is the “star sign”, which is a star-shaped trabecular structure in the weight-bearing area of the femoral head, a sign of microfracture and repair of bone trabeculae.
In 1996, Froberg proposed the following staging criteria for the CT presentation of osteonecrosis
Stage 0: normal.
Stage 1: coarsening of trabecular star-shaped structures, distortion and deformation and patchy high-density sclerotic areas and/or osteoporosis.
Stage 2: patchy osteosclerosis and cystic translucent areas with loss of trabecular awning structures.
Stage 3: crescentic sign with mild bone fragmentation and slight collapse of the articular surface on top of stage 2.
Stage 4: loss of femoral head integrity due to significant bone fragmentation and articular surface collapse.
Stage 5: Combination of femoral head hypertrophy deformity, acetabular rim hyperplasia and joint space narrowing.
IV. Magnetic resonance imaging (MRI).
MRI has become the “gold standard” for the examination and diagnosis of femoral head necrosis. MRI can effectively screen asymptomatic patients at high risk of osteonecrosis. 619 hips) did not present with significant hip symptoms, 100 of them showed manifestations of femoral head necrosis on MRI, and 11 of the 43 patients who presented with hip pain showed femoral head necrosis on MRI.
The typical presentation of early osteonecrosis on MRI is a moderate or low signal on T1-weighted images and a high signal on T2-weighted images. As the disease progresses, a “double line sign” appears, i.e. a circle of low signal around the necrotic area and a circle of high signal within the low signal line on the T2-weighted image. In progressive osteonecrosis, the necrotic area is hypointense on both T1- and T2-weighted images.
MRI is also important because it can accurately assess the extent of femoral head necrosis. The study by Bassounas AE et al. showed that the use of MRI to evaluate the volume of the necrotic portion of the femoral head is a good guide for clinical treatment selection.
There are several methods to measure the extent of necrosis?
One method, recommended by Steinberg in 1984, directly uses the abnormal area on the T1-weighted image to determine the percentage of necrotic area in the entire femoral head, which is divided into three categories: less than 15%, 15-30% and more than 30%.
Another method is to determine the extent of necrosis using the “necrotic area index”, which is calculated on MRI in the median coronal plane and median sagittal plane, respectively, as the “necrotic arc angel”, that is, the arc from the center of the femoral head to the edge of the necrotic area, labeled as A and B, respectively. The extent of necrosis was then calculated based on the A and B values. This method has the potential to underestimate the extent of necrosis and is improved by calculating the A and B values on the MRI image with the largest extent of necrosis.
In recent years, it has been reported in the literature that dynamic MRI is more effective for the early diagnosis of femoral head necrosis.Kaushik A et al. used dynamic MRI to study 30 patients (31 hips) with femoral neck fractures and obtained a significant correlation between imaging findings and changes in the blood supply to the femoral head.This study showed that dynamic MRI can predict ischemic femoral head necrosis within 48 hours based on the blood supply to the femoral head. necrosis can be predicted within 48 hours based on the blood supply to the femoral head.
V. Bone scan, bone scan is a functional examination. It reflects the blood flow and metabolism of bone tissue by the amount of radioactive technetium 99m taken up by bone tissue. Radionuclide bone scan is sensitive to the abnormalities of bone metabolism, and is very sensitive to the diagnosis of early femoral head necrosis. However, bone scan is a non-specific test, and a variety of diseases (such as tumors) can cause radioactive concentrations in the femoral head area, so careful differentiation should be made during diagnosis.
Early stage osteonecrosis is typically seen as a “cold zone” on bone scan, which is a low signal area in the subchondral osteonecrosis area, representing reduced uptake of nuclide, and is a sign of stage I osteonecrosis. In stage II osteonecrosis, a “hot zone” will appear around or within the “cold zone”, which is a reactive congested area with high signal, representing increased uptake of nuclide.
In recent years, bone scintigraphy has been used as a predictor of collapse in patients with early femoral head necrosis. Sedonja L et al [8] studied 27 patients (36 hips) and showed that the uptake of tracer at a particular stage of femoral head necrosis varies, and an increased tracer community predicts a high probability of collapse of the necrotic femoral head.
In addition to bone scan, single photon emission computed tomography (SPECT) significantly improves the sensitivity of diagnosing osteonecrosis.
Comparison of radiographs, CT, MRI and bone scan for the diagnosis of osteonecrosis shows that CT and MRI are the best means to assess the extent of the lesion, but bone scan is the most sensitive method for early diagnosis.
VI. Hemodynamic examination. For patients with normal radiographic presentation and no clinical symptoms, bone hemodynamic examination can help diagnose early femoral head necrosis. Generally, when the basal intraosseous pressure is greater than 4.0kPa, pressure test >1.3kPa, poor filling or retention of contrast agent, etc., the possibility of femoral head necrosis should be considered. It should be noted that hemodynamic examination is only suitable for early diagnosis, and is not accurate when the disease progresses to an advanced stage, when the articular cartilage breaks and collapses and causes the bone to connect with the joint space and the intraosseous pressure decreases, plus it is generally less used in clinical practice because it is an invasive examination method.
VII. Arteriography. It is generally believed that damage to the blood supply of the femoral head is the main cause of aseptic necrosis of the femoral head, and the abnormal changes of the arteries found in arteriography can provide a basis for early diagnosis of ischemic necrosis of the femoral head. Arteriography can clearly show the blood supply to the hip and femoral head. Common abnormalities of blood supply to the femoral head include: swelling and thickening of the main trunk of the internal rotor femoral artery or complete non-visibility, distortion, deformation, narrowing, interruption, hairy edges or complete non-visibility of the superior supporting band artery; distortion, deformation, thinning, thinning, interruption or complete non-visibility of the ascending branches of the external rotor femoral artery; reduction or increase of the ascending branches of the femoral head, the The parenchymal phase of the blood vessels of different shapes, densities and ranges in the neck stains; the fine arteries around the necrotic area are revascularized; the collateral circulation increases, and it is common that the internal spinofemoral artery anastomoses with the branches of the occluded artery, the upper and lower gluteal arteries or the external spinofemoral artery; the venous reflux is slow and stagnant, and the internal spinofemoral vein is more common.
Eight, arthroscopy. Arthroscopy is both a diagnostic method and a minimally invasive surgical treatment. For femoral head necrosis, arthroscopy can directly observe the joint surface of the femoral head; before the collapse of femoral head necrosis or osteoarthritis appears, synovial cleaning and other surgeries to preserve the femoral head can be performed. However, the significance of arthroscopy for early diagnosis of femoral head necrosis is not great. The common arthroscopic manifestations of femoral head necrosis are.
1, synovial changes, almost all synovial congestion, swelling and hyperplasia can be seen under arthroscopy at all stages, which may be an important cause of pain and an important factor in arthroscopic efficacy.
2, cartilage changes, early cartilage appearance and texture is normal, late weight-bearing area cartilage softening, fissures, and depressions on palpation, large necrotic exfoliation of cartilage will lead to cartilage defects on the surface of the femoral head.
3, subchondral bone, advanced necrosis area subchondral bone fissure formation, articular cartilage and subchondral bone separation; X-ray “crescent sign” is the weight-bearing area subchondral necrosis bone separation of the reflection; subchondral bone necrosis, collapse, fragmentation, exposed, etc., there may be ineffective repair of granulation tissue, necrosis bone surface hardening rough;. The joint gap is narrowed and the hip joint shows osteoarthritis-like changes.
The early diagnosis of femoral head necrosis should be considered in combination with clinical manifestations and various auxiliary examinations. In the early stage of femoral head necrosis, it is sometimes difficult to arrive at the diagnosis of ischemic necrosis of the femoral head. When encountering patients with suspected femoral head necrosis, the diagnosis should be confirmed or excluded on MRI and bone scan as much as possible. At the same time, careful clinical differentiation from other diseases (e.g., traumatic arthritis, congenital acetabular dysplasia with osteoarthritis, etc.) should be made to avoid misdiagnosis and missed diagnoses. Early diagnosis is a key factor in determining the therapeutic measures to be taken and must be taken seriously.