The role of imaging in diagnosis and management of femoral head avascular necrosis

Abstract

The aim of this paper is to critically review the literature documenting the imaging approach in adult Femoral Head Avascular Necrosis (FHAVN). For this purpose we described and evaluated different radiological techniques, such as X-ray, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and Nuclear Medicine. Plain films are considered the first line imaging technique due to its ability to depict femoral head morphological changes, to its low costs and high availability. CT is not a routinely performed technique, but is useful to rule out the presence of a subchondral fracture when MRI is doubtful or contraindicated. MRI is unanimously considered the gold standard technique in the early stages, being capable to detect bone marrow changes such as edema and sclerosis. It may be useful also to guide treatment and, as CT, it is a validated technique in follow-up of patients with FHAVN. Nuclear medicine imaging is mostly applied in post-operative period to detect graft viability or infective complications. More advanced techniques may be useful in particular conditions but still need to be validated; thus new research trials are desirable. In conclusion, X-ray examination is the first line approach, but lacks of sensitivity in early stage whereas MRI is indicated. CT easily depicts late stage deformation and may decrease MRI false positive results in detecting the subchondral fracture. However, the role of both Nuclear Medicine Imaging and advanced MR techniques in FHAVN still need to be investigated.

Keywords: diagnostic imaging; disease management; femur head necrosis; osteonecrosis.

Figure 1

Plain radiograph showing an area of lucency surrounded by a rim of sclerosis compatible with FHAVN.

Figure 2

Crescent sign at coronal T2 weighted images with associated initial articular deformity in the left femoral head in a 41-year-old patient.

Figure 3

T1 weighted (A) and T2 weighted (B) images show the “double line” sign associated with neck edema in the left femoral head of a 52-year-old male patient.

Figure 4

DWI image obtained from the same patient of Figure 3 showing increase diffusion in the left femoral head.

Figure 5

PET/CT showing intensive uptake in an area of osteonecrosis within the right femoral head in a 45-year-old asymptomatic patient.