Abstract
Introduction: Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) is a technique designed to measure early arthritis. Prior studies have shown the correlations between dGEMRIC index and the glycosaminoglycan (GAG) content of articular cartilage with a higher index indicative of more GAG content (healthier cartilage). There are also some reports on the utility of dGEMRIC index to document cartilage health prior to hip preservation surgery in an effort to predict treatment success in preventing the need for total hip replacement. Here we investigated the role of preoperative dGEMRIC in predicting the success of PAO in patients 40 and above. Methods: Following IRB approval, patients 40 or older who underwent PAO between 1990-2013 in our institute and had an available preoperative dGEMRIC scan and a minimum follow-up of 4 years were identified. Patients with prior hip surgeries or any pathologies other than hip dysplasia were removed leading to a total of 71 patients (Age: 44±3 years old). We only included the first hip undergoing PAO for those with bilateral PAO. Out of 71, 32 had failure defined by the need for total hip replacement or WOMAC pain score of 10 and above within 10 years after index PAO surgery. Femoroacetabular articular cartilage was segmented in 3D on a preoperative 6 echo contrast enhanced MRI to calculate average thickness and dGEMRIC index across the whole articular surface. Results: Patients who eventually failed PAO had significantly lower dGEMRIC index (409±70 vs 491±88; p<0.001). There were no differences in cartilage thickness between the groups (3.0±0.3 vs 2.9±0.3; P=0.26). Preoperative dGEMRIC index was able to discriminate between failed and asymptotic hips with 81% probability (AUC=0.81; p<0.001). A dGEMRIC index of 400 would discriminate between failed and asymptotic hips with a sensitivity of 52% and a specificity of 100%. Hips with a dGEMRIC index under 400 had a median survival time of only 4.2 years compared to 15.9 years for those with a dGEMRIC index over 400 (p<0.001). Discussion: The preoperative dGEMRIC was found as a robust prognostic tool for assessing the risk of postoperative failure in patients over the age of 40 undergoing PAO. A dGEMRIC index threshold of 400 delineates a critical boundary between PAO failure and joint preservation. For patients over 40 with symptomatic hip dysplasia presenting witha dGEMRIC index below this pivotal threshold, consideration of surgical alternatives to PAO may be warranted to optimize patient outcomes.