Paper # 56: Are Acetabular Chondral Flaps Worth Repairing: A Biochemical Assessment

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In this biochemical analysis of acetabular chondral flaps, no sample had a profile consistent with normal articular cartilage based on [DNA], [OH-Pro], and [GAG]. Arthroscopic techniques to repair acetabular chondral flaps have recently been published. However, the biochemistry of these chondral lesions has yet to be analyzed to determine if repair is reasonable. During hip arthroscopy, 21 acetabular chondral flap lesions were retrieved from 20 patients undergoing surgery for femoroacetabular impingement (FAI). These samples were analyzed for concentrations of DNA (an indicator of chondrocyte content), hydroxy-proline (OH-Pro, an indicator of collagen content), and GAG (an indicator of chondrocyte biosynthesis). The values were compared to studies of normal cartilage from the femoral head and condyle. Regression analysis was performed to determine whether the gross appearance of the cartilage, the type of FAI, or the demographics of the patient correlated with these markers of chondral health. The percentage of acetabular chondral flap specimens retrieved during hip arthroscopy that had concentrations above the minimal or within one standard deviation of the mean values reported in previous cartilage studies was 38% for [DNA], 43% for [OH-Pro], and 0% for [GAG]. 20% of our samples exceeded the threshold for both [DNA] and [OH-Pro]. The only significant correlation we found was between degenerative appearance of the surrounding cartilage and a higher [OH-Pro]: average ug OH-Pro/mg dry wt was 54 when there was degenerative-appearing surrounding cartilage and 47 when there was normal-appearing surrounding cartilage (p=0.030, spearman correlation, r=0.472). Otherwise, the gross appearance of the flap (i.e. thin vs. thick), gross appearance of the surrounding cartilage (normal vs. degenerative), type of impingement (cam, pincer, or both), age of the patient, gender of the patient, and duration of hip pain did not correlate to [DNA], [GAG], and [OH-Pro] (p>0.15 spearman correlation r < 0.31). None of the chondral lesions had a biochemical profile consistent with normal articular cartilage based on [DNA], [OH-Pro], and [GAG] as reported in the literature. 20% met the threshold of normal articular cartilage for just both [DNA] and [OH-Pro]. We did not find a correlation between any of the variables we examine (gross appearance, type of impingement, patient age, gender, and duration of symptoms) and the DNA, GAG, and OH-Pro concentrations of acetabular chondral lesions retrieved during hip arthroscopy except for a correlation between a degenerative surrounding cartilage and [OH-Pro]. These findings make determination of which chondral lesions to repair, if any, difficult.