The Bicep

Uploaded by Brainy81 on Dec 26, 2023

The Bicep


The long head of the biceps (LHB) brachii tendon originates at the supraglenoid tubercle and superior glenoid labrum. Its labral origin is mostly posterior in over half of cases, and the tendon, on average, is 9 cm in length. Inside the joint, the tendon is extrasynovial and passes obliquely, heading toward the bicipital groove. As it exits the distal bicipital groove in the upper arm, the long head of the biceps tendon joins the short head of the biceps tendon (SHBT) as both transition into their respective muscle bellies in the central third of the upper arm. After crossing the volar aspect of the elbow, the biceps brachii inserts on the radial tuberosity and medial forearm fascia. The latter occurs via the bicipital aponeurosis.[6]
The distal insertion point has become a relevant yet a controversial topic of interest. Over the last decade, there has been a renewed interest in investigating the insertional anatomy of the distal biceps tendon, specifically concerning its relevance in the evolution of distal biceps reconstruction techniques. Historically, the insertion site was described as one homogenous tendon that inserts on the radial tuberosity. More recent studies have reported its distal attachment as two distinct tendons. More specifically, recent studies have demonstrated the presence of an entirely bifurcated distal biceps tendon insertion. The studies found that the short head of the distal biceps tendon commonly inserts more distally than the long head and typically inserts at the apex of the tuberosity. The long head passes deep to the distal tendon of the short head before inserting proximal to the tendinous footprint of the short head.[7]


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Biomechanics
The biceps brachii muscle primarily is a strong forearm supinator but a weak elbow flexor.[8] Biomechanically, the long head of the biceps tendon has a controversial role in the dynamic stability of the shoulder joint. It has been demonstrated, mostly in biomechanical cadaveric-based studies and animal models, that the tendon at least plays a passive stabilizing role in the shoulder. Neer proposed in the 1970s that the long head of the biceps tendon's stabilizing role varied depending on the position of the elbow. Several subsequent studies refuted the theory that the long head of the biceps tendon played an active shoulder stabilizing effect.[9] Jobe and Perry evaluated the activation of the biceps during the throwing motion in athletes. The authors reported the peak muscle stimulation occurred in relation to elbow flexion and...