This discussion focuses on osteonecrosis of the femoral head in patients with HIV infection.
The pathogenesis of osteonecrosis is controversial, but likely involve interruption of the blood supply to the femoral head, which can result in demineralization and eventually collapse.
Osteonecrosis can be either asymptomatic (radiographic finding only) or symptomatic.
Patients with symptomatic osteonecrosis are more likely to have involvement of a greater portion of the femoral head than those with asymptomatic osteonecrosis.
Prevalence and Risk Factors
This patient’s persistent symptoms should raise suspicion for intraarticular hip pathology. Osteonecrosis is relatively common in HIV-infected patients, with prevalence estimates as high as 0.080% to 1.33%, as compared to 0.010% to 0.135% in the general population.
Many risk factors for osteonecrosis of the femoral head have been reported in the general medical literature. These include traumatic risk factors such as hip dislocation and acetabulum fracture, and non-traumatic risk factors such as corticosteroid use and alcohol use. In HIV-infected patients, reported risk factors include any lifetime use of systemic corticosteroids (even as little as days or weeks), hyperlipidemia, testosterone supplementation, previous AIDS-defining illness, and duration of exposure to antiretroviral therapy.
Osteonecrosis of the hip may be unilateral or bilateral, and may occur in the absence of identifiable risk factors. Pain is typically in the groin, but can also be in the buttock or thigh. It is exacerbated by weight bearing or moving the joint to the outer limits of its range of motion.
There are no physical exam findings that are characteristic of osteonecrosis. Currently, the recommended strategy is to do plain films of both hips and, if negative, bilateral hip MRI scans. MRI is the gold standard for diagnosis of osteonecrosis of the femoral head, because it has a very high sensitivity (> 90%) and allows for earlier detection than plain radiography. MRI should be performed in patients with hip pain and any risk factor for osteonecrosis.