Osteonecrosis of the femoral head is a consequence of insufficient vascular supply to the femoral head. Most cases are either idiopathic or associated with alcohol, corticosteroid therapy, or trauma. The condition manifests with groin pain, which may radiate to the knee or ipsilateral buttock, and a limited range of motion at the hip. Diagnosis is based on x-ray, followed by MRI. No curative treatments have been identified and there is no consensus on the best treatment options. Initial nonsurgical treatment focuses on preventing collapse of the femoral head, but surgical treatment is commonly required. Core decompression may improve the prognosis in early stages. If the disease progresses, arthroplasty may be necessary.
For avascular necrosis of the femoral head in children, see “Legg-Calvé-Perthes disease.”
- Peak incidence: 20–40 years 
Epidemiological data refers to the US, unless otherwise specified.
Though often idiopathic, several traumatic and atraumatic factors may contribute to the development of osteonecrosis.
Atraumatic factors 
- Glucocorticoid use (35–40% of cases)
- Alcohol use disorder (20–40% of cases)
- Hemoglobinopathies (e.g., sickle cell disease)
- Myeloproliferative disorders
- Autoimmune diseases (e.g., SLE, antiphospholipid syndrome)
- Hyperuricemia, hyperlipoproteinemia, diabetes mellitus
- Gaucher disease
- Decompression sickness
- Femoral neck fractures, particularly with dislocation 
- Femoral head fracture
- Slipped capital femoral epiphysis (SCFE)
ASEPTIC: Alcohol, Sickle cell disease/SLE, Exogenous steroid, Pancreatitis, Trauma, Infection, Caisson disease (decompression sickness)
Reduced blood supply and bone marrow infarction
The femoral head is at particular risk of developing avascular necrosis because there is an area of reduced vascularization (watershed zone) between the cranial and caudal parts.
- The cranial part receives blood from a branch of the obturator artery.
- The caudal part receives blood from medial and lateral femoral circumflex arteries.
- The foveolar artery is the main artery implicated in avascular necrosis of the femoral head
- Most commonly originates from the obturator artery and less commonly from the medial circumflex femoral artery 
- Passes through the ligament of the femur head
- Supplies the head of the femur
- The femoral head is at particular risk of developing avascular necrosis because there is an area of reduced vascularization (watershed zone) between the cranial and caudal parts.
- Slowly progressive groin pain, which may radiate to the knee or ipsilateral buttock 
- Limited active and passive range of motion at the hip
- Bilateral in 40–80% of cases 
Consider osteonecrosis in patients presenting with groin pain and a history of corticosteroid use or alcohol use disorder.
Diagnostic studies are used to rule out other causes of hip pain and allow for early detection and implementation of treatments to prevent and/or slow disease progression. 
X-ray: best initial test ;
- Recommended views: AP, frog-leg lateral, and oblique
- Findings 
MRI: confirmatory test
- Study of choice for early detection in clinically suspected cases with or without suspicious x-ray findings
- Findings 
- Visualization of the interface between necrotic and viable bone
- Bone marrow edema, joint effusion
- May show asymptomatic osteonecrosis of the contralateral hip
- CT: superior to MRI for detecting insufficiency fractures; also used for preoperative planning 
In patients with sickle cell anemia and osteonecrosis of the hip, consider evaluating for osteonecrosis of other joints. 
There are several staging systems for osteonecrosis of the femoral head; in general, the following four important findings are used to assess severity:
- Evidence of bone collapse or impending bone collapse
- Size of the necrotic component
- Amount of femoral head depression
- Acetabular involvement
Nonoperative management can provide relief in early stages of the disease, but operative treatment is usually necessary for most patients.
Nonoperative management: for symptomatic relief in early disease stages and patients who are not surgical candidates 
- Avoid weight-bearing on the affected side to prevent femoral head collapse.
- Address risk factors: e.g., smoking, alcohol use, corticosteroid use (if feasible)
- Pharmacological treatments are sometimes used, but there is a paucity of evidence on their efficacy.
Surgical treatment: may improve prognosis if performed in early stages 
- Interventions to prevent collapse of the femoral head
- Reconstructive procedures
- Resurfacing arthroplasty
- Total hip arthroplasty
- Femoral head collapse
- Secondary coxarthrosis
We list the most important complications. The selection is not exhaustive.