Quantitative MR Imaging Marker: Effective Cross-Sectional Area of the Rotator Cuff and Its Correlation with the Biodex Isokinetic Test.

Abstract

Objective: To evaluate the correlation between the effective cross-sectional area (eCSA) of the Rotator Cuff muscle measured using Dixon MRI and the outcomes of the Biodex Isokinetic Test.

Methods: The cross-sectional area (CSA) of the subscapularis (SSc), supraspinatus (SST), and infraspinatus+teres minor (ISTM) muscles of 87 patients who had undergone shoulder MRI and Biodex Isokinetic Test were measured in the oblique sagittal Y-view. The eCSA was calculated by multiplying the CSA by (1-fat fraction). Eight shoulder movements (FL60, EX60, FL180, EX180, ER60, IR60, ER180, and IR180) with four parameters (peak torque [PT], peak torque/body weight, torque at 30° [TQ30], and total work) were recorded on Biodex. Pearson correlation coefficients were calculated between eCSA and Biodex outcomes. Univariate regression analyses were conducted to identify the factors influencing the Biodex results. General linear models were applied to confirm the correlations between the eCSA and 32 Biodex parameters after adjusting for these factors.

Results: The eCSA of the SSc, SST, and ISTM exhibited significant correlations with TQ30 at IR180 (r=0.549) and FL60 (r=0.522), PT at ER60 (r=0.656) and EX60 (r=0.575), and PT at ER60 (r=0.674) and FL180 (r=0.626), respectively. Age, sex, SST, and SSc tears were identified as factors influencing the Biodex results. FL60TQ30, ER60PT, and EX60PT exhibited significant associations with the eCSA of SSc, SST, and ISTM, respectively, after adjusting for these factors.

Conclusion: eCSA may be a useful quantitative imaging marker for assessing the function of the Rotator Cuff muscle. FL60TQ30, ER60PT, and EX60PT are useful Biodex indices for SSc, SST, and ISTM, respectively.