MR arthrographic variability of the arthroscopically normal glenoid labrum: qualitative and quantitative assessment

The purpose of this study was to assess qualitatively and quantitatively th e MR arthrographic variability of the arthroscopically normal glenoid labru m. Form and signal abnormalities of arthroscopically normal labral parts we re analyzed on axial and coronal MR arthrograms of 55 consecutive patients (mean age 43.8 years, age range 21-76 years) referred mainly for suspected rotator cuff lesions. Length and width of the labrum were measured. One hun dred twenty-one of 241 (50 %) arthroscopically normal labral parts demonstr ated normal (low) signal intensity and normal form on MR arthrograms. Incre ased linear or globular signal intensity was present in 74 of 241 (31 %)nor mal labral parts, deformed or fragmented labra in 28 (12 %), complete separ ation of the labrum from the glenoid in 4 (2 %), a cleft in 5 (2 %), attenu ation in 4 (2 %),and complete absence in 5 (2 %), respectively. The mean si ze of the normal labrum varied between 3.8 x 3.3 mm at the subscapularis bu rsa level (anteriorly) and 6.1 x 5.6 mm at the inferior portion of the glen oid (anteriorly). The size was not significantly different between arthrosc opically normal and abnormal labral parts (p = 0.13-0.83). Since the MR app earance of the arthroscopically normal glenoid labrum varies considerably c oncerning signal intensity, form, and size, only major tears or detachments of the labrum should be diagnosed.