The long head of the biceps tendon (LHBT) is the proximal tendon of the long head of the biceps muscle and encircles the humeral head on its course. It has an intraarticular extrasynovial and an extraarticular portion.
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Summary
- location: shoulder
- insertion: supraglenoid tubercle of the scapula and superior labrum
- blood supply: anterior humeral circumflex artery, brachial and thoracoacromial arteries
- innervation: sympathetic fibers
- relations: superior labrum, rotator interval, biceps pulley, pectoralis major insertion
- function: stabilizer of the glenohumeral joint
Gross anatomy
The long head of the biceps tendon has an intraarticular and extrasynovial portion spanning the anterior aspect of the humeral head covered by synovium from the joint capsule that extends into the bicipital groove. The tendon originates from the superior aspect of the glenoid and superior labrum, courses through the rotator interval beneath the coracohumeral ligament and through the bicipital groove 1-3.
Function
Functions of the long head biceps tendon include 2-4:
- force transmission created by the biceps muscle
- stabilization of glenohumeral joint especially in the abduction and external rotation
Attachments
The tendon originates from the supraglenoid tubercle and superior labrum mostly with predominant contributions from the posterior labrum or equal contributions from anterior and posterior labrum 5.
Its myotendinous junction is at the proximal humerus at the level of the insertion of the pectoralis major muscle 2.
Relations and boundaries
Above the humeral head and the long head biceps tendon courses through the rotator interval and is bordered by the structures of the biceps pulley 3:
- coracohumeral ligament superiorly
- superior glenohumeral ligament anteriorly and inferiorly
- supraspinatus tendon posterosuperiorly
- subscapularis tendon anteroinferiorly
Within the bicipital groove, the long head biceps tendon is bordered by the lesser tubercle anteriorly, the greater tubercle posteriorly and covered by the transverse humeral ligament 1.
The distal part and its myotendinous junction are covered by the pectoralis major tendon.
Arterial supply
The proximal part of the long head biceps including parts of the bicipital groove appears to be mainly supplied from branches of the anterior humeral circumflex artery 6. The further distal portions receive their supply from the brachial and thoracoacromial arteries 4,7.
Innervation
The long head biceps tendon is innervated by sensory sympathetic fibers especially its proximal portion 3.
Variant anatomy
Anatomical variants include the following 3,8,9:
- congenital absence of the long head biceps tendon
- double or triple tendon with common or separate origin
- adherence to the supraspinatus muscle or joint capsule
- variations in the mesotenon
Radiographic features
The long head biceps tendon can be nicely evaluated on soft-tissue imaging modalities as ultrasound and MRI 3.
Ultrasound
Ultrasound can readily identify the long head biceps tendon in the bicipital groove beneath the transverse humeral ligament usually with a minimal amount of surrounding fluid. From there it can be traced upwards through the rotator interval to its origin at the superior glenoid. It should not be thickened and show any tears or fiber discontinuities – beware of anisotropy 10.
MRI
The long head biceps tendon can be readily seen on MRI of the shoulder as a hypointense string-like structure encircling the humeral head. It can be affected by the magic angle effect especially in the curve as it encircles the humeral head and enters the bicipital groove.
Moreover, MRI can depict most biceps tendon pathologies except for isolated pulley lesions 3.
MR arthrography
MR arthrography can be used in the detection of biceps pulley injuries and has been shown to have a high accuracy 11.
Related pathology
The following pathologies can be associated with the long head biceps tendon 1-3:
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