Global Fatty Degeneration Index on Preoperative MRI Predicts Early Postoperative Shoulder Stiffness at 3 Months Following Primary Rotator Cuff Repair

Purpose: To determine if the fatty infiltration of rotator cuff muscles, as measured by magnetic resonance imaging (MRI) preoperatively and assessed using the Goutallier Fatty Degeneration Index (GFDI), can predict early post-operative shoulder stiffness (POSS) following rotator cuff repair (RCR).

Methods: This retrospective longitudinal cohort study included patients who underwent primary RCR, had available medical records, and underwent MRI before RCR between November 2012 and July 2022. Patients were excluded based on the following criteria: (1) preoperative shoulder stiffness, (2) additional procedures (e.g., biceps tenodesis, labrum repair, stabilization for instability, and distal clavicle resection), and (3) inadequate medical records. Patient demographics, comorbidities, fatty infiltration based on the Goutallier classification from preoperative MRI scans and GFDI scores-calculated from the supraspinatus, infraspinatus, and subscapularis muscles-were recorded. POSS was defined based on range of motion at the 3-month postoperative assessment. Chi-square tests and independent t-tests were used for group comparisons. Receiver operating characteristic (ROC) curve analysis determined optimal GFDI cutoff values, and logistic regression assessed POSS risk associated with GFDI.

Results: A total of 388 patients were included; 128 patients were in the POSS group and 260 in the non-POSS group at the 3-month follow-up. Fatty infiltration of the supraspinatus, infraspinatus, and subscapularis muscles was significantly higher in the POSS group compared to the non-POSS group. ROC analysis yielded an area under the curve of 74.1% for GFDI≥ 1.5, with a sensitivity of 83.6% and specificity of 58.8%. Logistic regression revealed an adjusted odds ratio of 5.733 for POSS with mean GFDI≥ 1.5 (P = 0.003).

Conclusions: Increased fatty infiltration in the rotator cuff muscles, particularly with GFDI≥1.5, is associated with a higher risk of early POSS three months after surgery.

Level of evidence: Level III, Retrospective Case-Control study.