Demystifying Radial Imaging of the Hip

Abstract

The hip joint poses unique challenges at magnetic resonance (MR) imaging because of its shape and anatomic position. When conventional imaging planes are used, partial-volume averaging effects may substantially hamper the depiction of cartilage and labral damage at MR imaging. Such effects are most prevalent when the imaging plane is not perpendicular to the curvature of the joint and result in images that poorly depict or fail to depict cartilage and labral conditions. Partial-volume averaging, along with the inherently thin and closely apposed articular cartilage, may be partly to blame for the seemingly disparate reported sensitivities of MR imaging for depicting cartilage damage in the literature, which vary widely depending on whether arthrography was used. Fortunately, the multiplanar capability of MR imaging is not limited to standard anatomic planes. Radial sections, which are obtained perpendicular to the surfaces of the hip joint, provide a true cross section of the cartilage and labrum that conventional planes do not. Radial imaging is a reproducible technique that enhances the morphologic assessment of the articular cartilage and labrum. The additional information it provides is important because early damage occurs in the anterosuperior region of the hip in patients with femoroacetabular impingement.

MRI for the preoperative evaluation of femoroacetabular impingement

“…This allows evaluation of osseous abnormalities, labral and chondral lesions, and measurement of alpha angles in different clock-face locations [35]. By convention, 12 o'clock refers to the superior hip joint, and 3 o'clock refers to the anterior aspect of the hip joint bilaterally.…”

Evaluation of the Articular Cartilage of the Knee Joint Using an Isotropic Resolution 3D Fast Spin-Echo Sequence With Conventional and Radial Reformatted Images

“…In particular, radial imaging has been used in the hip for years with mixed results in terms of improvement in the detection of joint abnormalities [30][31][32][33]. Theoretically, radial sections offer improved characterization of curved articular surfaces by providing an orthogonal view at each surface point, which minimizes the effects of partial volume averaging [34]. The purpose of this study was to determine whether the use of radial reformatted images could improve the diagnostic performance of a 3D FSE sequence for detecting surgically confirmed cartilage lesions within the knee joint.…”

Rapid Radial T1 and T2 Mapping of the Hip Articular Cartilage With Magnetic Resonance Fingerprinting

“…Magnetic resonance imaging (MRI) is a powerful tool for noninvasive evaluation of joints, but the hip joint poses unique challenges to it. In particular, its shape and anatomic position, including its thin and closely apposed articular cartilage, make hip MRI susceptible to partial‐volume averaging utilizing conventional imaging planes …”