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

Abstract

Purpose: 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.

Keywords: MR arthrography; SLAP lesions; anatomical variants; instability shoulder; long head biceps; shoulder.

Figure 1

Magnetic resonance arthrography, SE T1w image on oblique sagit tal plane. Normal course of long head biceps (LHB) tendon (arrow) that seems to be free in intra-articular position, contrast agent is located between LHB tendon and supraspinatus tendon (asterisk)

Figure 2

Magnetic resonance arthrography. SE T1w image on oblique sagittal plane. ADH-CL anatomic variation, long head biceps tendon is adherent to supraspinatus tendon, without contrast agent between these tendons (arrow)

Figure 3

Magnetic resonance arthrography. A) SE T1w image on oblique coronal plane, through sections 1 and 2. ADH-PL anatomic variation, long head biceps (LHB) is adherent to supraspinatus tendon only in its lateral portion (arrow), while on medial portion there is agent contrast between LHB and supraspinatus tendon (asterisk). B) T1w FAT SAT image with isotropic voxel on axial plane. SPL-DO anatomic variation, LHB has double origin from supraspinatus tendon (curved arrow) and from glenoid (black arrow)

Figure 4

Magnetic resonance arthrography. SE T1w image on oblique sagittal plane. A) MESO-PU anatomical variant, thin intra-articular hypointense hammock- like sling around the long head biceps (LHB) tendon (arrows). B) MESO-PA anatomical variant, LHB tendon is partially attached to inferior surface of supraspinatus tendon (arrow), contrast agent forms an obtuse angle with the anterior portion of the LHB tendon and an acute angle with the posterior portion

Figure 5

Magnetic resonance arthrography. A) SE T1w image on oblique coronal plane. MESO-SB anatomical variant with thin intra-articular hypointense synovial band (arrow), which from medial to lateral connects the rotator cuff with the biceps. B) SE T1w image on oblique sagittal plane. MESO-VI anatomical variant, biceps is connected to the rotator cuff through an hypointense intra-articular fine string with vertical course (arrow)

Figure 6

Magnetic resonance arthrography. SE T1w image on the oblique sagittal plane. Site of long head biceps anchor on the glenoid (arrow): at 12 o’clock (A), more anterior at 1 o’clock (B), and more posterior at 11 o’clock (C)

Figure 7

Magnetic resonance arthrography. SE T1w image on the oblique sagittal plane. Long head biceps tendon’s thickness and shape (arrow): oval (A), rounded (B), or flat (C)

Figure 8

Schematic representation of glenoid “clockface” proposed mechanism for association between a predominantly posterior LHB attachment and posterior tears: A) A completely posterior attachment (red) effectively counteracts the vectors (black arrow) that normally promote humeral subluxation in abduction/external rotation. B) As the site of maximal vector force is fixed, with a predominantly posterior attachment, the unequal distribution of the tendon fibres over the vector site leads to partial opposing forces to humeral subluxation leading to a progressive lift off of the biceps tendon at its posterior labral attachment (posterior tears with progressive lift off indicated by lighter shades of pink)