Variations in branching of the posterior cord of brachial plexus in a Kenyan population

Abstract

BackgroundVariations in the branching of posterior cord are important during surgical approaches to the axilla and upper arm, administration of anesthetic blocks, interpreting effects of nervous compressions and in repair of plexus injuries. The patterns of branching show population differences. Data from the African population is scarce.ObjectiveTo describe the branching pattern of the posterior cord in a Kenyan population.Materials and methodsSeventy-five brachial plexuses from 68 formalin fixed cadavers were explored by gross dissection. Origin and order of branching of the posterior cord was recorded. Representative photographs were then taken using a digital camera (Sony Cybershot R, W200, 7.2 Megapixels).ResultsOnly 8 out of 75 (10.7%) posterior cords showed the classical branching pattern. Forty three (57.3%) lower subscapular, 8(10.3%) thoracodorsal and 8(10.3%) upper subscapular nerves came from the axillary nerve instead of directly from posterior cord. A new finding was that in 4(5.3%) and in 3(4%) the medial cutaneous nerves of the arm and forearm respectively originated from the posterior cord in contrast to their usual origin from the medial cord.ConclusionsMajority of posterior cords in studied population display a wide range of variations. Anesthesiologists administering local anesthetic blocks, clinicians interpreting effects of nerve injuries of the upper limb and surgeons operating in the axilla should be aware of these patterns to avoid inadvertent injury. A wider study of the branching pattern of infraclavicular brachial plexus is recommended.

Study of Variations in the Branching Pattern and Distance of Origin of Branches of Posterior Cord of Brachial Plexus

“…Muthoka et al noted that UTA (L) R was the most frequent order of branching pattern seen in 32 (42.7%) cases [22]. This is in correlation with the present study.…”

“…encountered that upper subscapular nerve was given off by the posterior cord in 54 (72%) and originated as a single nerve in 56 (74.6%) specimens and as 2 separate branches in 5 (6.7%) specimens [22].…”

Study of Variations in the Origin of Axillary Nerve From the Posterior Cord of Brachial Plexus and Its Clinical Importance

“…The variations occur at the junction or separation of individual parts and may be due to an unusual formation during the development of the trunks, divisions, or cords [8]. Muthoka [13] studied 75 brachial plexus in Kenyan population and found a wide range of variations in the order of branching of posterior cord. Some of his variations included a common trunk for axillary, thoracodorsal & lower subscapular from posterior cord and a common trunk for upper, middle, lower subscapular & axillary nerve.…”

“…Further, identification of specific nerves originating from posterior cord of brachial plexus is necessary during neurotisation processes. Clinically, trauma of the posterior wall of the axillary region could present with a wide range of degrees of muscle impairment For instance, lesions involving common trunk for axillary nerves and thoracodorsal nerve may produce more extensive functional lesions including lattisimus dorsi, deltoid and teres minor muscles [7,13]. The shoulder joint dislocation and rotator cuff tear causes nerve injury which is called "unhappy triad" of the shoulder joint.…”

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“…This is concordant with a report by Kumar [6] in one case from 47 cadavers. This rare variation may be caused by the segmental origin of the axillary artery and its branching which may determine the arrangement of the brachial plexus during fetal development [16].…”