A Quantitative Fatty Infiltration Evaluation of the Supraspinatus Muscle: Enhanced Clinical Relevance and Improved Diagnostic Value on Predicting Retear Compared With the Goutallier Classification

Background: Preoperative assessment of fatty degeneration is important for managing rotator cuff tears. The Goutallier classification is semiquantitative and observer dependent. Discrepancies among surgeons can be prominent. A quantitative method may improve accuracy and reliability in evaluating the exact percentage of fatty infiltration (Fat%). Hypothesis/Purpose: This study aimed to investigate the correlation between the new quantitative method and the Goutallier classification in assessing fatty infiltration (FI) of the supraspinatus muscle and to explore the use of this method in predicting retear after rotator cuff repair. It was hypothesized that the new method would significantly correlate with the Goutallier classification and be more sensitive to retear. Study Design: Cohort study (diagnosis); Level of evidence; 3. Methods: This study included 105 patients who underwent arthroscopic rotator cuff repair for large to massive tears. All patients underwent routine preoperative and 1-year postoperative magnetic resonance imaging and were divided into 2 groups according to tendon healing. Preoperative quantitative Fat% of the supraspinatus muscle was evaluated based on the signal intensity (SI) of the T1-weighted sequence. The Fat% was calculated using the following equation: SI supraspinatus = SI fat × Fat% + SI muscle × (1 – Fat%). The correlation between the Fat% and the Goutallier grade was determined. Univariate and multivariate analyses were performed to identify the independent risk factors for retear. Results: The mean preoperative Fat% of the supraspinatus muscle was 23.77 ± 15.96. A significant correlation was found between the Fat% and the Goutallier grade of the supraspinatus muscle ( R = 0.655; P < .001). The overall retear rate was 21.9%; however, functional status significantly improved regardless of cuff healing. Multivariate analysis identified the Fat% ( P = .005) and the modified Patte classification ( P = .003) as independent risk factors of retear. The receiver operating characteristic curves showed that the cutoff value of Fat% for predicting retear was 33.2%. Fat% >33.2% possessed superior diagnostic accuracy (79.0%), Youden index (0.513), and positive and negative predictive values (51.6% and 90.5%, respectively) compared with the Goutallier grades. Conclusion: Although the quantitative method for assessing Fat% of the supraspinatus muscle significantly correlated with the Goutallier classification, the quantitative method is more clinically relevant to retear. Fat% of the supraspinatus muscle >33.2% possessed higher diagnostic value than the Goutallier grades in predicting retear.