Atrophy and fatty infiltration of the supraspinatus muscle: sonography versus MRI.
OBJECTIVE
The objective of our study was to compare sonography with MRI for the evaluation of supraspinatus muscle atrophy and fatty infiltration.


METHODS
Forty-five shoulders in 39 patients who had undergone shoulder MRI for the assessment of rotator cuff disease were evaluated blindly with sonography. Supraspinatus muscle atrophy was quantitatively assessed by calculating the occupation ratio (cross-sectional surface area of the supraspinatus muscle belly divided by that of its fossa). This was done by reproducing on sonography the equivalent of the "Y" view on MRI. Fatty infiltration was assessed by evaluating supraspinatus muscle echogenicity compared with that of the trapezius muscle and pennate pattern. The occupation ratio and fatty infiltration of the supraspinatus muscle on sonography were compared with these findings on MRI.


RESULTS
Occupation ratios calculated on sonography images ranged from 0.07 (severe atrophy) to 0.81 (normal) and correlated with the ratios calculated on MRI (R = 0.90; 95% CI, 0.83-0.95). All 20 shoulders with no fatty infiltration on MRI had normal echogenicity and a pennate pattern on sonography. Eight of the 10 shoulders with mild fatty infiltration on MRI had an effaced pennate pattern and mild hyperechogenicity on sonography. In 13 of the 15 shoulders with moderate to severe fatty infiltration on MRI, the pennate pattern was absent and marked hyperechogenicity was present on sonography.


CONCLUSIONS
Our study suggests that there is a good correlation between sonography and MRI for the assessment of supraspinatus muscle atrophy and fatty infiltration.
Khoury
Viviane
V
Department of Diagnostic Radiology, McGill University Health Center, Montreal General Hospital, 1650 Cedar Ave., Montreal, QC H3G 1A4, Canada. viviane.khoury@hotmail.com
Cardinal
Etienne
E
Brassard
Paul
P
D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000473:pathology; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology*; D009133:Muscular Atrophy / Q000000981:diagnostic imaging / Q000473:pathology; D017006:Rotator Cuff / Q000000981:diagnostic imaging; D000070636:Rotator Cuff Injuries; D014463:Ultrasonography