AUTHORS: Marie-Pierre Ingham (Université de Montréal), Mahsa Shakeri (Polytechnique Montréal), Shirin Shakeri (Polytechnique Montréal), Karim Saydy (Université de Montréal), Samuel Kadoury (Polytechnique Montréal), Nathalie J Bureau (Centre hospitalier de l’Université de Montréal).

OBJECTIVE: To assess supraspinatus muscle volumetric and 3D shape alterations in patients with full-thickness rotator cuff tears (RCT).

METHOD: Retrospective study in 47 patients with RCT (mean age, 57 years; range, 39-67 years) and 30 asymptomatic volunteers (mean age, 56 years; range, 35-64 years). Morphometric assessment of the entire supraspinatus muscle was performed by 2 independent readers, with good interobserver reliability (ICC=0.916), on large field-of-view coronal oblique T1-weighted MR scans. The supraspinatus muscle was segmented using ITK-SNAP tool. Volume, length, surface area, surface-to-volume ratio (S/V), and 3D shape statistical analysis were computed in Matlab. ANOVA with covariates (height, sex and BMI), multiple comparisons and a non-parametric permutation testing scheme were used to test for significant differences (p<0.05) between patients, volunteers and RCT Patte classification subgroups. 

RESULTS: Supraspinatus mean volume (p<0.001) and surface area (p<0.001) were smaller in patients compared to volunteers, whereas mean S/V was greater (p<0.001) and no difference in mean length was observed (p=0.318). Group-wise shape differences occurred mostly in the caudal aspect of the muscle (Figure 1). Similarly, as tendon retraction increased (Patte 1, 2, 3), supraspinatus mean volume (p<0.001) decreased, surface area (p < 0.001) decreased and the mean S/V (p=0.026) increased. The mean length decreases but the difference is not significant (p=0.304). 

CONCLUSION: The supraspinatus muscle atrophies but does not contract significantly as tendon tear size increases. Its posterior head (caudal portion) is more affected by this volume reduction than its anterior head.

3D MORPHOMETRIC ANALYSIS OF THE SUPRASPINATUS MUSCLE IN ROTATOR CUFF TEAR PATIENTS