TP2.1 Progressive Biological Recovery of the Acetabular Labrum After Arthroscopic Surgery for Femoroacetabular Impingement: A Quantitative MRI Study

Abstract Introduction Femoroacetabular impingement (FAI) is a major cause of hip pain, and the acetabular labrum plays a critical role in joint stability and function. Arthroscopic surgery increasingly emphasizes labral preservation and repair. However, the postoperative biological status of the labrum remains unclear. Magnetic resonance imaging (MRI) enables noninvasive assessment of soft tissue, and signal intensity may reflect tissue quality. This study aimed to evaluate temporal changes in labral signal intensity following arthroscopic surgery for FAI. Methods A total of 41 hips (28 males, 13 females; mean age 44 years) with cam-type (28 hips) or mixed-type (13 hips) FAI were included. MRI was performed preoperatively and at 6 months and 1 year postoperatively using a 3-T system with radial T2* sequences. Signal intensity of the labrum and gluteus medius was measured using a 2.5-mm region of interest at the 12, 1, and 2 o’clock positions. The labrum-to–gluteus medius signal intensity ratio was calculated to reduce variability. Temporal changes were analyzed using the Friedman test. Results At the 12 o’clock position, the ratio increased slightly from 0.61 preoperatively to 0.63 at 6 months, then decreased to 0.56 at 1 year. At the 1 o’clock position, the ratio decreased from 0.78 to 0.71 and 0.66, showing a significant difference across time points (p < 0.05). At the 2 o’clock position, the ratio decreased from 0.84 to 0.73 and 0.69. The highest values were consistently observed at the 2 o’clock position at all time points. Discussion Labral signal intensity decreased over time after arthroscopic surgery for FAI, particularly in the anterior region, suggesting progressive biological recovery. As T2*-weighted signal intensity reflects tissue hydration and organization, the observed reduction may indicate maturation of the repaired labrum. Importantly, signal intensity continued to decrease between 6 months and 1 year, suggesting that labral healing is an ongoing process that extends beyond the early postoperative period. These findings indicate that at least one year may be required for substantial biological recovery of the labrum. MRI-based quantitative assessment may provide a useful tool for evaluating postoperative healing.