Dooley Noted: 4/26/2016
The long head of biceps brachii (LHBB) muscle is a longitudinal elbow and shoulder flexor.
Due to its proximity to the skin’s surface, one can easily visualize this muscle at its joint belly with short head of biceps brachii (SHBB).
LHBB’s superior tendon is different than the SHBB, since its tendon sits in a deep groove between two bony lips at the humerus. At this location, the tendon is wrapped in a synovial sheath that resembles a bursa, as it anchors itself to the local periosteum.
The LHBB is tacked into place by a transverse humeral ligament, to help it stay in its anatomical position for biomechanical advantage. Then, the tendon goes intracapsular, as it enters the glenohumeral joint to attach to the supraglenoid tubercle of the scapula.
Due to its proximity to labral attachments, it’s not uncommon for LHBB to anchor itself to the glenoid labrum.
The clinical implications for LHBB include the following:
1. Irritation of its tendon’s synovial sheath
2. Displacement of the LHBB tendon
3. Superior labrum anterior to posterior (SLAP) tears
LHBB irritation mimics subacromial bursitis, due to its proximity to the coracoid process.
Patients will almost always point to the anterior part of the shoulder, where they will roll around the LHBB tendon and complain of sharp pain when it is palpated.
LHBB is anchored via their joint belly to SHBB, making LHBB a slave to what’s happening at the coracoid process of the scapula.
Four vital muscles attach to the coracoid process:
A. SHBB
B. Pectoralis minor
C. Coracobrachialis
D. Occasionally, a slip from subclavius
With postural tendencies favoring gravity and flexion, muscles A-D tend toward concentric (shortened) positions.
This will lead to LHBB being dragged medially towards the coracoid process, resulting in irritation of the synovial sheath.
Additionally, the transverse humeral ligament can loosen or even rupture, allowing A-D to more easily move the LHBB medially.
This medial displacement will create potential for synovial sheath irritation and subsequent potential for pain afference.
In throwing or overhead athletes, the LHBB often becomes compromised at the glenohumeral joint.
As postures get carried into sports, LHBB positioning is slightly altered. Couple that with athletes that lacks upper thoracic spinal mobility, and they will compensate with excessive force generated at the shoulder.
LHBB tends to lack its freedom and extensibility due to the aforementioned compromises, leaving it susceptible to tearing from its scapular position as the overhead position is initiated.
It’s typically a case of LHBB being overused eccentrically at the shoulder without proper extensibility, leading to it tearing and taking the glenoid labrum with it.
To improve LHBB positioning and mechanics, consider the spinal action and scapulothoracic joint function as the primary areas of focus.
Many people who lack thoracic mobility and/or lumbar stability will swing that club or bat with their shoulder joints.
The shoulder joints are delivery systems for force, and they were never meant to be force generators.
Also, if there’s no healthy balance between scapular protraction and retraction, then the scapula stays protracted and LHBB is compromised.
Make sure the glenohumeral joint is not the force generator for an energy leak in the abdomen. Then, make sure the scapulothoracic kinetic issues are resolved.
This will protect LHBB and decrease potential for irritation of its synovial sheath.
As always, it’s your call.
– Dr. Kathy Dooley