What diagnostic method is most appropriate for assessing hip avascular necrosis?

In assessing hip avascular necrosis, MRI is the most appropriate diagnostic method due to its high sensitivity and specificity for detecting early changes in bone and soft tissue. Avascular necrosis, particularly in its initial stages, may not be evident on X-rays, as it can take several weeks or even months for changes to become visible as bone remodeling and collapse occur.

MRI provides excellent detail of the bone marrow, allowing for the identification of subtle changes such as bone edema, which are indicative of early avascular necrosis. It can visualize the extent and location of necrosis more effectively than other imaging modalities, making it a critical tool for diagnosis and management of the condition.

While X-rays and CT scans can be useful in later stages to assess fractures or joint collapse, MRI's ability to detect early pathology makes it the preferred method in cases of suspected avascular necrosis. Ultrasound is less commonly used for this condition as it offers limited information on the internal structure of the bone itself.