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

Introduction
Anatomical variants of the long head of the biceps (LHB) and diseases of the rotator interval structures may contribute to shoulder instability. The rotator interval and the LHB tendon are closely associated anatomic structures that confer stability to the shoulder. Anatomical variants around the origins of the long head of the biceps (LHB) are reported to occur with a frequency of 1.9-7.4%. In the past years, many authors have proposed different approaches for the identification and characterization of LHB and rotators interval. Magnetic resonance (MR) arthrography is considered the reference standard in imaging to diagnose superior shoulder diseases. However, few authors have analysed the anatomical variants and the relation between those and shoulder instability. This study aimed to identify the frequency of variants observed during arthroscopic shoulder surgeries, and to classify them based on the Dierickx classification system.

Material and methods
In 326 MR arthrograms we investigated the incidence of LHB anatomical variations and their association with shoulder diseases.

Results
We found 252/326 (77.3%) cases of LHB free, 40/326(12.26%) cases of LHB adherent, 31/326(9.50%) cases of mesotenon, and 3/326(0.9%) cases of split biceps. The prevalence of rotator interval synovitis in the mesotenon group was greater than in the LHB-free group. Moreover, in the LHB-adherent group we observed increased incidence of sublabral recess and SLAP lesions compared with the LHB-free group.

Conclusions
MR-arthrography is useful in the evaluation of superior shoulder structures. A relationship exists between LHB anomalies and superior shoulder instability.