Long Head of Biceps Tendonitis
The long head of the biceps tendon (LHBT) seems to play a major role in the generation of pain within the shoulder, (Elser et al., 2011). There is controversy regarding the biomechanics and the function of the LHBT, as well as the pathology associated with the tendon, (Paynter K.S, 2004). A lack of understanding of the LHBT makes treatment difficult, and the complexity of the shoulder joint means that treating patients with LHBT problems is difficult.
LHBT attaches to the supraglenoid tubercle and the glenoid labrum of the shoulder joint, with some variants, (Friedman et al., 2008, Tuoheti et al., 2005). In contrast to the distal tendon, the proximal tendon is wider and more densely innervated with sensory fibres containing substance P and calcitonin gene-related peptide, both of which contribute to vasodilation, plasma extravasation and pain transmission, (Krupp et al., 2009, Ryu &Pedowtiz., 2010); the neural network becomes sparser more distally within the tendon, (Alpantaki et al., 2005). The LHBT tendon is approximately 9 cm long; the proximal attachment is encased in synovium as it passes through the rotator interval stabilised by a sling, which consists of the coracohumeral ligament, superior glenohumeral ligament and the fibres of the supraspinatus along with the subscapularis tendons, (Habermeyer et al., 2004). LHBT then passes into the biciptal groove, between the greater and lesser tubercle, where the transverse ligament covers the tendon, although current research suggests that it is not a major stabilizing structure, (Baber et al., 2007). The bicipital groove has a mean depth of 4.3 mm, allowing the tendon through to join with the short head of the biceps tendon forming the biceps muscle belly, (Friedman et al., 2008).
Function of the LHBT at the glenohumeral joint is still controversial and not completely understood, (Ejnisman et al., 2010), although electromyographic data support the role of biceps as a humeral head depressor, (Friedman et al., 2008). The biceps extends from the scapula to the forearm, functioning at both the shoulder and the elbow joints, (Krupp et al., 2009). Neer (1972) suggested that the biceps tendon affects glenohumeral stability, possibly as a result of the positions of the shoulder and elbow joints; a proprioceptive function in the biceps has yet to be established, (Ryu & Pedowitz., 2010). Considering long bones of the body with attached muscles which cross 2 joints (eg: the femur, quadriceps and hamstrings; the humerus, triceps and biceps), this situation should in theory be well suited to facilitate coordinated proprioceptive feedback and neuromuscular control, as opposed to maximising joint torque, (Ryu & Pedowitz, 2010). However, as yet this concept is unproven for the biceps tendon specifically.
There have been several biomechanical studies looking at glenohumeral stability in relation to the biceps tendon. Pagnani et al. (1996) reported that contraction of the biceps limits glenohumeral translation. In addition, Rodosky et al. (1994) demonstrated that stimulated contraction of the biceps increases the stability of the glenohumeral joint by increasing the shoulder’s resistance to torsional forces. It is suggested, therefore, that the biceps is not an active stabiliser of the shoulder, but the LHBT may contribute passively.
Disorders of LHBT tend to arise from inflammatory changes in the intertubercular groove, which could develop as a result of instability or injury, (Friedman et al., 2008). Disorders of the LHBT are currently broken down into three categories: inflammatory/degenerative, instability of the biceps tendon, and traumatic, such as SLAP (“Superior Labral tear from Anterior to Posterior”) lesions. Within these three categories all patients present with shoulder pain, irrespective of pathogenesis, (Krupp et al., 2009). LHBT disorders have also been categorised as tendonitis or overuse injury; tendonitis indicates acute inflammation, whereas overuse suggests chronicity and is caused by a repetitive movement.
Primary biceps tendonitis occurs with inflammation of the LHBT within the intertubercular groove or if changes occur within the groove without any pathological changes within the shoulder, (Hsu et al., 2008); this should therefore be considered as a tenosynovitis, meaning inflammation of the sheath rather than the tendon, which accounts for approximately 5% of biceps tendonitis, (Favorito et al., 2001).
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