Natural History Of Quantitative Fatty Infiltration And 3D Muscle Volume After Nonoperative Treatment Of Symptomatic Rotator Cuff Tears.

Abstract

Aim: The purpose of this investigation was to quantitatively analyze supraspinatus (SSP) muscle fatty infiltration (FI) and volume at the initial presentation and after a 3-month minimum of conservative management. We hypothesized that progression of FI could be predicted with initial tear size, FI, and muscle volume. Background(s): The severity of FI predicts the treatment outcome of rotator cuff tears. Method(s): Seventy-nine shoulders with rotator cuff tears were prospectively enrolled, and 2 magnetic resonance imaging (MRI) scans with 6-point Dixon sequences were acquired. The fat fraction within the SSP muscle was measured on 3 sagittal slices, and the arithmetic mean was calculated (FISSP). Advanced FISSP was defined as >=8%, pathological FISSP was defined as >=13.5%, and relevant progression was defined as a >=4.5% increase in FISSP. Furthermore, muscle volume, tear location, size, and Goutallier grade were evaluated. Result(s): Fifty-seven shoulders (72.1%) had normal FISSP, 13 (16.5%) had advanced FISSP, and 9 (11.4%) had pathological FISSP at the initial MRI scan. Eleven shoulders (13.9%) showed a >=4.5% increase in FISSP at 19.5+/-14.7 months, and 17 shoulders (21.5%) showed a >=5-mm3 loss of volume at 17.8+/-15.3 months. Five tears (7.1%) with initially normal or advanced FISSP turned pathological. These tears, compared with tears that were not pathological, had significantly higher initial mediolateral tear size (24.8 compared with 14.3 mm; p=0.05), less volume (23.5 compared with 34.2 mm3; p=0.024), more FISSP (9.6% compared with 5.6%; p=0.026), and increased progression of FISSP (8.6% compared with 0.5%; p<0.001). An initial mediolateral tear size of >=20 mm yielded a relevant FISSP progression rate of 81.8% (odds ratio [OR], 19.0; p<0.001). Progression rates of 72.7% were found for both initial FISSP of >=9.9% (OR, 17.5; p<0.001) and an initial anteroposterior tear size of >=17 mm (OR, 8.0; p=0.003). Combining these parameters in a logistic regression analysis led to an area under the curve (AUC) of 0.913. The correlation between FISSP progression and the time between MRI scans was low positive (rho=0.31). Conclusion(s): Three risk factors for relevant FI progression, quantifiable on the initial MRI, were identified: >=20-mm mediolateral tear size, >=9.9% FISSP, and >=17-mm anteroposterior tear size. These thresholds were associated with a higher risk of tear progression: 19 times higher for >=20-mm mediolateral tear size, 17.5 times higher for >=9.9% FISSP, and 8 times higher for >=17-mm anteroposterior tear size. The presence of all 3 yielded a 91% chance of >=4.5% progression of FISSP within a mean of 19.5 months.Copyright © 2024