Osteonecrosis of the femoral head (ONFH), also known as ischemic necrosis of the femoral head (AVN), is a common intractable disease in the field of orthopedics Definition: ONFH is a disease in which the blood supply to the femoral head is interrupted or impaired, causing death of bone cells and bone marrow components and subsequent repair, which subsequently leads to structural changes in the femoral head, femoral head collapse and joint dysfunction. ONFH can be divided into two categories: traumatic and non-traumatic. The former is mainly caused by hip trauma such as femoral neck fracture and hip dislocation, while the main causes of the latter in China are corticosteroid application and alcohol abuse. Diagnostic criteria Experts suggest that the diagnostic criteria proposed by the Japan Institute of Osteonecrosis (JIC) and Mont be integrated to develop our diagnostic criteria. I. Main criteria 1. Clinical symptoms, signs and history: arthralgia mainly in the groin and hip and thigh area, limited internal rotation of the hip joint, history of hip trauma, history of corticosteroid application, history of alcoholism. 2.X-ray changes: femoral head collapse without joint space narrowing; sclerotic zone with demarcation within the femoral head; subchondral bone with transverse X-ray zone (crescent sign, subchondral fracture). 3.Nuclear scan shows a cold zone in the hot zone within the femoral head. 4, T1-weighted phase of MRI of the femoral head shows banded low signal (banding type) or T2-weighted phase with double line sign. 5.Bone biopsy shows more than 50% osteocyte vacuolation fossa of bone trabeculae, and involves adjacent multiple bone trabeculae with bone marrow necrosis. Secondary criteria 1. X-ray shows femoral head collapse with narrowing of joint space, cystic degeneration or speckled sclerosis in the femoral head, and flattening of the outer upper part of the femoral head. 2.Nucleus bone scan shows cold or hot areas. 3, MRI shows a band type with homogeneous or heterogeneous low signal intensity without T1 phase. The diagnosis can be confirmed if two or more major criteria are met. Meeting one major criterion, or ≥4 positive secondary criteria (including at least one positive radiographic change), is likely to be diagnostic.