Femoral head necrosis is a common, frequent and intractable disease in orthopedics, mostly occurring in young and middle-aged people between the ages of 30 and 50. In the United States, 15,000 to 20,000 new cases of osteonecrosis of the femoral head occur each year, and osteonecrosis of the femoral head accounts for 5% to 10% of the total number of hip replacement patients, and 70% of them involve bilateral hip joints. In Asian countries, especially China, Japan and Korea, the incidence of femoral head necrosis is higher. The main cause of femoral head necrosis in Asian countries is alcohol consumption, followed by the application of glucocorticoids. And the incidence of hormonal necrosis is higher than alcoholic femoral head necrosis in European and American countries.
I. Etiology and high-risk groups
There are many possible causes of femoral head necrosis, such as trauma, excessive alcohol consumption, hormone abuse, and some hematological diseases, etc. Some causes are unknown as idiopathic.
1. Trauma is the most common cause of femoral head necrosis. Intracapsular femoral neck fractures such as head-down type and diameter-neck type can directly damage the epiphyseal vessels, round ligament vessels, or form intra-articular hematoma, increasing intracapsular pressure, thus blocking the blood supply and reflux of the joint capsule and forming femoral head necrosis, with an incidence of 11% to 45% reported in the literature. The incidence of femoral head necrosis in displaced fractures is more than twice as high as that in nondisplaced fractures. Femoral head necrosis due to femoral fracture mostly occurs within 2 years after the fracture heals, and the sudden pain in the anterior hip area is often the first manifestation.
2.Population of hormone use
Glucocorticoids have been widely used in the treatment of rheumatoid, systemic lupus erythematosus, dry syndrome, nephrotic syndrome, fundus disease, malignant tumors and other diseases, about 40% of hormone users can eventually develop osteonecrosis, of which osteonecrosis of the femoral head is the most common. It is generally believed that osteonecrosis may occur when the cumulative dosage of prednisone exceeds 2000mg. During the first 6 months of hormone use, the risk of osteonecrosis of the femoral head increases 4.6-fold with 10 mg of oral prednisone daily.
Short-term high doses of hormones can significantly increase the risk of osteonecrosis, while in some cases osteonecrosis can occur with low doses of hormones. Some reports suggest that femoral head necrosis can still occur after 3 years of hormone use, but most studies show that hormonal head necrosis mostly occurs within 3 to 6 months after hormone use; therefore, close observation should be made during hormone use for early detection. In addition, hormonal osteonecrosis usually develops rapidly, because hormones can also cause osteoporosis, resulting in a decrease in the strength of the subchondral bone in the necrotic area, and early collapse of the femoral head can occur.
3.Alcoholic people
According to foreign reports, alcoholic femoral head necrosis accounts for 20-40% of all cases of necrosis, and its bilateral incidence can be as high as 73%, alcohol intake and femoral head necrosis is positively correlated, the weekly alcohol intake within 400ml, the incidence of femoral head necrosis is 3 times higher than normal, if the weekly intake of more than 400ml, the incidence of femoral head necrosis is 11 times higher than normal.
Excessive intake of alcohol can lead to fat deposition in the liver, and the fat deposited in the liver can produce a large number of tiny fat emboli, which can directly block the blood vessels supplying the femoral head or hydrolyze into free fatty acids in the bone, causing vascular endothelial damage, thus damaging the blood supply to the femoral head.
Clinical manifestations
The first symptom of femoral head necrosis is pain in the anterior region of the hip joint (inguinal region). Some people have pain in the inner thigh muscles or the inner knee joint, which is most likely to be missed. Very few patients present with pain in the posterior gluteal region (which can be easily confused with a herniated disc). The pain may be constant or intermittent. In some patients, the symptoms are temporarily and completely relieved by rest. The pain may increase suddenly after exertion or minor trauma, and gradually worsen with the development of the disease. The pressure point is located in the interguinal area.
The most effective non-invasive early diagnosis method is magnetic resonance imaging (MRI), while X-ray plain film and CT scan cannot be used for early diagnosis.
III. Pathological histological progression process
After 12 hours of ischemia in the femoral head, cells begin to damage necrosis and bone marrow edema, followed by inflammatory reaction with macrophage and neutrophil infiltration, which shows bone marrow edema signal in the femoral head on MRI, and this process lasts for several days before it shows osteonecrosis, after which the process of tissue repair appears vascular growth into the lesion, macrophages and osteoclasts enter the lesion to clean up the necrotic bone marrow and dead bone, and accompanied by At the edge of the necrotic area, osteoblasts begin to synthesize new bone, which in most cases is directly over the surface of the necrotic trabeculae, at which point the histology shows a thickening of the trabeculae and the appearance of a sclerotic zone around the necrotic area on x-ray and CT.
The T2-weighted image on MRI shows the typical bilinear sign of a high signal at the periphery of the necrotic area, a zone of edema reaction and a low signal band of new bone at the edge of the necrosis. If the necrotic area is relatively small and not in the main weight-bearing zone of the femoral head, the lesion may be partially or completely repaired and can be asymptomatic. Larger lesions, especially in weight-bearing areas, usually have a poor prognosis. Because of the limited vascular penetration to reach the deeper parts of larger lesions, deep repair is interrupted and these dead bones can develop fragmentation fractures. Because the resorption of necrotic bone is faster than bone formation, the necrotic area is significantly weaker and the subarticular trabeculae appear to collapse, resulting in a “crescentic sign” on imaging.
If left untreated, flattening of the femoral head will occur rapidly. Due to the change of stress, the articular cartilage cells of the femoral head and acetabulum are damaged and die, the joint space is narrowed, and finally, the advanced arthritis such as subchondral osteosclerosis and cystic degeneration appears on the imaging.
Fourth, the current domestic “head preservation” treatment methods
(I) Restrictive weight-bearing
Femoral head necrosis causes a decrease in bone mechanics strength, reduce the weight-bearing of the affected hip, in order to avoid the collapse of the femoral head during the repair period of osteonecrosis. Studies on the natural history of femoral head necrosis have shown that femoral head necrosis has the potential to repair itself.
(ii) Drug treatment
1, fat embolism, adipocyte hypertrophy, venous thrombosis increased intraosseous pressure, weakened osteogenic capacity and enhanced bone breaking are considered as factors for the development of femoral head necrosis. Based on these views, lipid-lowering drugs, anticoagulants, vasodilators and diphosphonates are used in the treatment of osteonecrosis of the femoral head.
Commonly used drugs are: lovastatin
hydroxymethylpyrazole
Iloprost
Enoxaparin
Alendronate
The above drugs are used under the guidance of physicians according to specific conditions.
2, Chinese medicine dialectical treatment: Chinese medicine has good effect on patients within steinberg stage III, the treatment period is long, it takes about 1 to 2 years. For patients with steinberg stage III or above, it can also significantly relieve the pain symptoms. However, the improvement on imaging is often not obvious.
(iii) Surgical treatment
1.Simple medullary decompression
Medullary decompression of the femoral head is the most common method used to treat early femoral head necrosis. This method can reduce the increased pressure in the femoral head to reduce the pain symptoms, and through the drilling channel of the vascular bone into, prompting the crawling replacement of new bone in the osteonecrosis area. The success rate is 78% in Ficat I, 62% in Ficat II and 41% in Ficat III.
2.Femoral bone core decompression + structural bone support and blood flow reconstruction
This procedure is based on the decompression of the medullary core, together with bone grafting, in order to improve the structural support of the necrotic area of the femoral head and prevent the femoral head from collapsing during the repair period. The free vascularized fibula graft technique is a common approach for the treatment of femoral head necrosis. It has a high success rate in cases without preoperative collapse of the subchondral bone and articular cartilage of the femoral head. Others are autologous cancellous bone compression-supported bone grafting. This procedure is less invasive and relatively simple to operate, and is suitable for patients with ARCO stage II-III.
3.Titanium mesh support treatment for femoral squared bone column
This new procedure not only retains the advantages of the femoral square bone column grafting, but also further increases the support strength through titanium mesh, which is easier to ensure the blood flow of the bone column with the tip, so it is more advantageous for ARCO IIC and IIIA femoral head necrosis, and the operation is less traumatic and easy, which is a new direction for the treatment of femoral head necrosis.
4. Porous metal tantalum rod implantation
It is used to treat early femoral head necrosis. The porous tantalum rod for reconstruction of femoral head necrosis has the characteristics of reliable and rapid bone growth and reduced stress masking, and has good biocompatibility, human bone tissue can grow well into the pores of the metal tantalum rod, so that human bone and metal tantalum rod are integrated, so it is also called metal bone trabeculae, which has a good supporting effect on the femoral head that will collapse. It delays the collapse of the femoral head, postpones the time of hip replacement, and avoids the blood supply damage caused by the blood-bearing bone and fibula graft.
The above treatment methods are widely carried out in our department, and have achieved good results. For clearly diagnosed femoral head necrosis, we should do our best to stop or delay the progression of the disease and preserve the patient’s own femoral head, which is the goal we pursue and the direction we strive for.