Abstract
BACKGROUND: The purpose of this work is to characterize the anatomy of the intraarticular portion of the long head of the biceps tendon (long head biceps tendon) using magnetic resonance (MR) arthrography by investigating whether anatomical variants may facilitate the onset of a supraequatorial lesion (superior labral anterior to posterior, SLAP). MATERIALS AND METHODS: In 482 shoulder MR arthrographies, we considered the anatomical variants of the intraarticular portion of the long head of the biceps tendon classified according to Dierickx's arthroscopic classification; lesions of supraequatorial structures were considered in the data analysis. For each anatomical variant, correlation with SLAP and the odd ratio were statistically evaluated, using Fisher's exact (or chi-squared) test and logistic regression analysis, respectively. RESULTS: In the mesotenon-type variant, the SLAP frequency was higher than expected [χ(2) (df = 4) = 14.9, p = 0.005] with a higher risk of developing a type I SLAP (p = 0.0003). In the adherent-type variant, the type II SLAP frequency was higher than expected [χ(2) (df = 3) = 18.1, p = 0.0004] with a higher risk of developing type II SLAP (p = 0.0001). Two cases of "split" (SPL) long head biceps tendon had III and type IV SLAP, respectively. These patients have a higher risk for type IV SLAP [odds ratio (OR) 19.562, 95% confidence interval (CI) 1.604-238.541, p = 0.001]. An increased risk of developing SLAP type II was calculated for male subjects (OR 3.479, 95% CI 1.013-11.951, p = 0.019). CONCLUSIONS: It is possible that adherence of the long head biceps tendon to the supraspinatus more often predisposes to a lesion of the superior glenoid labrum (SLAP), in view of the close relationships between the fibrocartilage and the bicipital anchor, probably related to the limited excursion of the intraarticular long head biceps tendon.