Why does femoral head necrosis occur? Is conservative treatment effective?

Author: Guo Xiaozhong, Chief Physician, First Affiliated Hospital of Tsinghua University

Reviewer: Li Jun, Chief Physician, Peking University First Hospital

Femoral head necrosis, also known as avascular necrosis of the femoral head, is caused by interruption or damage to the blood supply to the femoral head, which causes the death of bone cells and bone marrow components and subsequent repair, leading to changes and collapse in the structure of the femoral head. Femoral head necrosis can occur at any age, but is more common in people aged 20-45.

Figure 1 Original copyright image, no permission to reprint

The blood supply to the femoral head mainly has three branches. The medial femoral circumflex artery mainly supplies blood to the proximal femoral head and weight-bearing area; the lateral femoral circumflex artery is mainly responsible for the blood supply to the distal non-weight-bearing area below the femoral head; when young, there is a small concave artery, which mainly supplies blood to the area around the head concave of the femoral head. After adulthood, the small concave artery gradually becomes occluded, and the blood supply to the femoral head is mainly supplied by the medial femoral circumflex artery and the lateral femoral circumflex artery.

The main cause of avascular necrosis of the femoral head is the blockage of the capillaries entering the femoral head from the ascending branch of the medial femoral circumflex artery, which is caused by the increase of fat particles inside the blood vessels. In addition, blood flow obstruction to the femoral head may also originate from external factors of the blood vessels, such as the enlargement of fat cells between capillaries and the increase of fat particles. If the blood supply to the bone tissue and connective tissue in the femoral head is not smooth, it will cause cell apoptosis, mainly osteocyte apoptosis. After osteocyte apoptosis, cavities appear in the bone lacuna, and the trabeculae are broken. When more trabeculae are lost, the supporting force of the femoral head will be greatly affected. Coupled with daily walking, running and jumping, the femoral head will collapse. As the collapse continues to worsen, it will develop from the early stage to the late stage of femoral head necrosis.

There are several main causes of femoral head necrosis: ① Use of hormones. Patients need to take hormones for a long time due to other diseases, and the cumulative medication time is up to one week or even longer than one month, which is also related to the peak dosage, that is, the maximum dosage. The longer the hormone is taken, the higher the probability of osteonecrosis. ② Long-term and heavy drinking. Drinking for more than ten years, the longer the duration, the more alcohol consumed per week, the higher the chance of osteonecrosis. ③ Trauma. Trauma causes femoral neck fracture or hip dislocation, and damages the blood supply to the femoral head, which may cause femoral head necrosis. ④ Other rare causes: such as thalassemia, altitude sickness, decompression sickness, etc., may also cause certain damage to the blood supply to the femoral head, causing ischemic necrosis of the femoral head.

When avascular necrosis of the femoral head occurs, hip pain will first occur, pain in the front of the groin area, and can also radiate to the hip area, or even to the back, or to the knee joint. Many patients who experience leg pain mistakenly believe that there is a problem with the knee joint or lumbar spine, so femoral head necrosis is easily missed or misdiagnosed, and the missed and misdiagnosis rates are relatively high. The misdiagnosis rate of the initial visit can be as high as 40% or more.

Figure 2 Original copyright image, no permission to reprint

Discomfort and pain around the hip joint may occur intermittently, or obvious hip pain may occur due to a certain movement. At this time, it should be taken seriously. Of course, femoral head necrosis will also have certain signs, such as limited hip joint movement, especially when flexion and internal rotation are more obvious. As the disease progresses, the movement restriction will become more and more severe, and the pain will increase when carrying weight, running and jumping.

If hip pain occurs and femoral head necrosis is suspected, the doctor will first do a physical examination to see if the hip joint movement is restricted. If the hip joint movement is restricted, an X-ray examination will be done first. Early femoral head necrosis will show a decrease in bone density on the X-ray. If the disease progression is not particularly obvious, it is often easy to miss or misdiagnose. Femoral head necrosis is considered in the early stage. Magnetic resonance imaging is a very sensitive and specific examination that can detect more than 98% of femoral head necrosis. Once some specific imaging signs appear, such as the "double line sign" and "crescent sign", the accuracy of diagnosing femoral head necrosis is very high.

There are many conservative treatments for femoral head necrosis, including Chinese medicine and Western medicine. Chinese medicine includes drugs that promote blood circulation and remove blood stasis, remove dead tissue and regenerate new bone, or dilate blood vessels and promote circulation; Western medicine includes drugs that dilate blood vessels, increase calcium absorption, and prevent bone absorption. At present, there is no sufficient evidence to prove that drug treatment of femoral head necrosis has a good clinical effect.

Other conservative treatments include hyperbaric oxygen, ozone therapy, ultrasound therapy, magnetic therapy, electrotherapy, etc. However, these methods are not currently supported by literature, which means that there is insufficient evidence to prove that they have a definite therapeutic effect on femoral head necrosis. If there is no effect after treatment, it will often delay the disease, causing it to be delayed from the early stage to the later stage, and miss the treatment opportunity for head-saving surgery.

It usually takes several months, half a year, a year, or two to three years from the onset of symptoms to the collapse of the femoral head. Most cases gradually become more serious as the disease progresses. If effective intervention treatment is not carried out during this period, conservative treatment alone will not achieve very good therapeutic effects. Conservative treatment combined with rest can relieve pain symptoms, but it will not help delay the progression of the disease.

Most patients with femoral head necrosis will face surgical treatment, which includes two types of surgery: surgery to preserve the femoral head and artificial hip replacement. Surgery to preserve the femoral head includes core decompression, bone grafting, osteotomy, etc., which is suitable for patients in relatively early stages.