What is osteonecrosis? Osteonecrosis, also known as aseptic osteonecrosis or ischemic osteonecrosis, refers to the pathological process caused by the death of viable components of bone (including bone cells, bone marrow hematopoietic cells and adipocytes). It is commonly found in the femoral head, humeral head, femoral condyles, proximal tibia, and bone tissue of the foot, ankle, and wrist, with the femoral head being the most susceptible and often involved bilaterally. Therefore, this article mainly discusses aseptic necrosis of the femoral head as an example. Second, how can we detect osteonecrosis of the femoral head at an early stage? 1, pay attention to the sensitive factors related to the development of femoral head necrosis Trauma (especially femoral neck fracture), decompression sickness, radiation injury, Gaucher’s disease, hemoglobinopathy, long-term use of steroid corticosteroids, alcoholism, etc. Trauma, alcohol and hormone are the three most common clinical causes. 2, clinical manifestations Femoral head necrosis early symptoms less or even no performance, pain is often the earliest symptoms of femoral head necrosis, usually chronic hidden pain, but the pain symptoms are not long-term persistent, by rest or reduce activity, symptoms often reduce or disappear on their own. Some patients only feel discomfort in the hip, buttock and the back of the thigh, and there may be varying degrees of swelling and joint dysfunction in the painful area. These mild symptoms are often overlooked by patients. In addition, these symptoms are not specific, and the receiving doctor lacks experience or the equipment of the hospital is limited, so the disease is often missed or misdiagnosed as “rheumatism” or “lumbar disc herniation” and other diseases. This pain can occur before or after a positive x-ray finding. Patients with femoral head necrosis may develop claudication and disuse atrophy of the muscles of the affected limb at a later stage. The affected hip is restricted in all directions, mainly in internal rotation and abduction, with pressure pain at the midpoint of the groin and muscle atrophy in the quadriceps muscle. 3, auxiliary examination ① X-ray examination X-ray is currently the most commonly used method to diagnose osteonecrosis, and is also a common and effective method to observe the effect of osteonecrosis treatment, with the characteristics of simple, intuitive, convenient and economic. However, the discovery time lags behind, which is not conducive to early examination. In the early stage, there is often no positive manifestation on the X-ray film. In the middle stage, obvious necrotic areas, decreased and increased bone density appear at the same time, positive “crescent sign”, and collapse of the bone area can be seen. In the later stage, the subchondral bone plate and articular surface collapse, bone contour change, stepped discontinuity, bone compression increase, while the acetabular articular surface is also damaged, joint space narrowing and bone redundancy formation. ②Isotope scan The diagnostic sensitivity of ischemic osteonecrosis is 80%, and it reflects the lesion earlier than conventional X-ray examination. ③CT examination CT has the characteristics of high resolution and accurate contrast, which can make the diagnosis of osteonecrosis earlier than X-ray film, with a sensitivity of 90% or more and high specificity. CT manifestation of osteonecrosis: early stage shows normal or stellate structure deformation, thickening and disorder of weight-bearing bone trabeculae, visible limited cystic change sparse area and scattered speckled calcification area; middle and late stage shows bone contour deformation, fragmentation and marrow cavity sclerosis, etc. MRI is the most sensitive method for the diagnosis of osteonecrosis, and has the characteristics of ideal display of the morphology, structure and function of the skeletal system, which is significantly better than X-ray, CT examination and isotope scan. ⑤ Other tests such as hemodynamic examination of bone, arteriography, and puncture biopsy are often helpful for the early diagnosis of osteonecrosis. Its blood examination is often non-specific, in order to differential diagnosis, the blood alkaline phosphatase, rheumatoid factor, blood sedimentation and other tests can be done. 4.Our suggestion Pay attention to the relevant pathogenic triggers, the performance of individual clinical symptoms, regular imaging examinations, timely consultation with experts, is the best way to detect and exclude osteonecrosis.