Intra-articular long head of the biceps tendon: magnetic resonance-arthrography classification and review of literature

Imaging of Anatomical Variants of the Long Head Biceps Tendon

Anatomical variants of the long head of biceps (LHB) tendon are widely discussed in the literature. As one of the few intra-articular tendons, magnetic resonance arthroscopy can quickly evaluate the proximal part of LHB morphology. It provides good assessment of both intra-articular and extra-articular portions of the tendons. In-depth knowledge about imaging of the anatomical LHB variants discussed in this article is useful preoperatively for orthopaedists and also helps avoid potential diagnostic misinterpretations.

MR arthrography: correlation between anatomic intraarticular variants of the long head of the biceps tendon (long head biceps tendon) and superior labral anterior to posterior (SLAP) lesions

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 [χ² (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 [χ² (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.

Anatomical variants of the intraarticular portion of the long head of the biceps tendon should be studied with MR arthrography.

Some anatomical variants are more frequently associated with supraequatorial lesions.

The higher frequency of lesions in the presence of certain anatomical variants is probably related to the limited excursion of the intraarticular long head biceps tendon.