musculoskeletal and connective tissue disorders
Osteonecrosis (ON)
Etiology of Osteonecrosis
The most common cause of osteonecrosis is trauma, and the most common cause of nontraumatic osteonecrosis is corticosteroid use. The most common cause of traumatic osteonecrosis is a displaced subcapital Hip Fractures ; osteonecrosis is uncommon after intertrochanteric fractures. The incidence of osteonecrosis after hip dislocation is related primarily to the severity of the initial injury but may be higher if the dislocation is not promptly reduced. Fracture or dislocation may cause osteonecrosis by grossly disrupting or compressing nearby blood vessels. Nontraumatic osteonecrosis affects men more often than women, is bilateral in>60% of cases, and occurs primarily in patients between ages 30 and 50. The most common factors causing or contributing to nontraumatic osteonecrosis are Corticosteroid use (particularly with prolonged use and/or higher doses) Excessive alcohol consumption Other nontraumatic risk factors for osteonecrosis include Chemotherapy Coagulation disorders (eg, Antiphospholipid Syndrome (APS) , inherited thrombophilia, hypofibrinolytic disorders) Cushing Syndrome None Decompression Sickness None Dyslipidemia None Gaucher Disease None Hemoglobinopathy (eg, Sickle Cell Disease ) Human Immunodeficiency Virus (HIV) Infection None Liver disease Organ Overview of Transplantation None Overview of Pancreatitis None Radiation Smoking Systemic Lupus Erythematosus (SLE) and other Tumors Miscellaneous disorders (eg, Chronic Kidney Disease , rare The contribution of corticosteroid use to the risk of osteonecrosis is increased when the dose ofprednisoneor an equivalent corticosteroid is>20 mg/day for several weeks or months, resulting in a cumulative dose usually>2000 mg, although case reports have described osteonecrosis subsequent to much less corticosteroid exposure. Notably corticosteroid-associated osteonecrosis is often multifocal and can affect both weight-bearing as well as non–weight-bearing joints like the shoulders. The risk of osteonecrosis is also increased when>3 drinks/day (>500 mLethanol/week) are consumed for several years. or to anticardiolipin antibodies (see Overview of Thrombotic Disorders ) can be detected in a high percentage of patients with osteonecrosis. Some disorders that are common comorbidities of osteonecrosis are treated with corticosteroids (eg, systemic lupus erythematosus). Evidence suggests that the risk of osteonecrosis in many of these disorders is related primarily to the corticosteroid use rather than to the disorder. About 20% of cases of osteonecrosis are idiopathic. Medication-Related Osteonecrosis of the Jaw (MRONJ) has been reported in patients who have received bisphosphonate therapy (particularly with IV administration) and other antiresorptive agents (eg, The term "spontaneous osteonecrosis of the knee" (SONK) is a misnomer. This condition normally occurs in older patients and is localized to the femoral condyle or tibial plateau. SONK is thought to be caused by an insufficiency fracture (a type of fragility fracture caused by normal wear and tear on osteoporotic bone that occurs without direct trauma). True osteonecrosis of the knee can result from trauma or any of the nontraumatic risk factors of osteonecrosis. 