CURRENT AND FUTURE ADVANCED IMAGING MODALITIES FOR THE DIAGNOSIS OF EARLY OSTEOARTHRITIS OF THE HIP
Figure 1 - dGEMRIC images of weight-beating Hip cartilage in a healthy volunteer (left) and a patient with early osteoarthritis (right).
Hip osteoarthritis (OA) can be idiopathic or develop secondary to structural joint abnormalities of the hip joint (alteration of normal anatomy) and/or due to a systemic condition with joint involvement. Early osteoarthritic changes to the hip can be completely asymptomatic or may cause the development hip symptomatology without evidence of OA on radiographs. Delaying the progression of hip OA is critical due to the significant impact of this condition on the patient's quality of life. Pre-OA of the hip is a newly established term that is often described as the development of signs and symptoms of degenerative hip disease but no radiographic evidence of OA. Advanced imaging methods can help to diagnose pre-OA of the hip in patients with hip pain and normal radiographs or aid in the surveillance of asymptomatic patients with an underlying hip diagnosis that is known to increase the risk of early OA of the hip. These methods include the delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC), quantitative magnetic resonance imaging (qMRI- T1rho, T2, and T2* relaxation time mapping), 7-Tesla MRI, computed tomography (CT), and optical coherence tomography (OCT). dGEMRIC proved to be a reliable and accurate modality though it is limited by the significant time necessary for contrast washout between scans. This disadvantage is potentially overcome by T2 weighted MRIs, which do not require contrast. 7-Tesla MRI is a promising development for enhanced imaging resolution compared to 1.5 and 3T MRIs. This technique does require additional optimization and development prior to widespread clinical use. The purpose of this review was to summarize the results of translational and clinical studies investigating the utilization of the above-mentioned imaging modalities to diagnose hip pre-OA, with special focus on recent research evaluating their implementation into clinical practice.
Figure 2 - High resolution axial spoiled gradient echo (GRE) images of the Hip region with 3 Tesla (left) and 7 Tesla (right) MRI (A and B) with flip angles (C and D). Quantitative signal-to-noise ratio maps of GRE images are shown in (E and F).
Conclusion
Pre-OA of the hip is a newly recognized term to describe early, potentially modifiable degenerative changes in the hip that are often not detectable with conventional imaging modalities. Current research suggests that certain dGEMRIC and qMRI protocols could reliably diagnose pre-OA hip disease, but more research is necessary to allow for their implementation into clinical practice. CT has limited use in the detection of pre-OA, but it is a valuable tool in the work up and preoperative planning for associated conditions such as FAI and DDH. The benefits of using any CT imaging modality must be balanced with the risks of ionizing radiation in a young patient population.
Figure 3 - Optical Coherence Tomography (left) and equivalent histological sections (right) according to the graded classification system of Bear et al. Grade (A) indicates an intact surface and obvious birefringence, grade (B) represents an intact surface with no birefringence, and grade (C) corresponds to an irregular articular surface and/or subsurface voids.
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Published September 14, 2022 in Orthopedic Research and Reviews.