Delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) Predicts the Pattern of Hip Osteoarthritis Progression at Five-Year Follow-Up

Abstract

Femoroacetabular impingement increases the risk of developing hip osteoarthritis, however, morphological parameters have a low positive predictive value. Arthroscopic debridement of impingement lesions has been proposed as a potential means of preventing osteoarthritis, but the development of such strategies requires identification of individuals at high risk of disease progression. We investigated whether delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) predicts the development of osteoarthritis at 5-year follow-up. This imaging modality is an indirect measure of cartilage glycosaminoglycan content. Patients were selected from a prospective cohort study. 34 asymptomatic individuals with a normal joint space width (JSW) (>2.5mm) were assessed at baseline with collection of Patient Reported Outcome Measures, anteroposterior and cross-table lateral radiographs, 3D morphological MRI, and dGEMRIC at 3T of their index hip. A dGEMRIC ratio was calculated as a ratio of the anterosuperior acetabular cartilage T1 relaxation time and the total femoral and acetabular cartilage T1 relaxation time. 29 individuals were followed up at 5 years for repeat assessment (14 female and 15 male, mean age 51 years, range 36 to 67). Radiological measurements were made by a single observer using in house software. Radiographic disease progression was assessed using minimum JSW, lateral sourcil JSW, and medial sourcil JSW. These were measured on baseline and 5 year follow-up anteroposterior radiographs with an intraobserver ICC of 0.916. Alpha angle measurements were made by the same observer on radiographs and MRI radial slices with an intraobserver ICC of 0.926. Mean minimum JSW for the cohort fell by 0.16 mm over 5 years (p=0.024). Baseline dGEMRIC ratio did not correlate with change in minimum JSW (r=0.031; p=0.873) but did correlate with JSW narrowing at the lateral sourcil (r=0.531; p=0.003) and the direction of JSW narrowing (change in JSW at the lateral sourcil minus change in JSW at the medial sourcil) (r=0.561; p=0.002). Mean maximum alpha angle measured on baseline MRI radial slices (mean 79.6 degrees, range 49.2 to 116.2) did not correlate with change in minimum JSW and weakly correlated with JSW narrowing at the lateral sourcil (r=0.253; p=0.195) and the direction of JSW narrowing (r=0.273; p=0.160). There was a weak correlation between the change in Non-Arthritic Hip Score and baseline dGEMRIC (r=0.256; P=0.180). A low dGEMRIC ratio indicates reduced glycosaminoglycan concentration in the anterosuperior acetabular cartilage compared with the total femoral and acetabular cartilage. This correlates with lateral JSW narrowing relative to medial JSW narrowing as osteoarthritis progresses. The dGEMRIC ratio correlates better with osteoarthritis progression than alpha angle measurements and offers the potential to refine a predictive model for osteoarthritis progression to aid patient selection for clinical trials.