Anatomy of axillary nerve and its clinical importance: a cadaveric study

Axillary nerve is one of the terminal branches of posterior cord of brachial plexus, which is most commonly injured during numerous orthopaedic surgeries, during shoulder dislocation & rotator cuff tear. All these possible iatrogenic injuries are because of lack of awareness of anatomical variations of the nerve. Therefore, it is very much necessary to explore its possible variations and guide the surgeons to enhance the better clinical outcome by reducing the risk and complications.

Twenty five cadavers (20 Males & 05 Females) making 50 specimens including both right and left sides were dissected as per standard dissection methods to find the origin, course, branches, distribution & exact location of the nerve beneath the deltoid muscle from important landmarks like: posterolateral aspect of acromion process, anteromedial aspect of tip of coracoid process, midpoint of deltoid muscle insertion (deltoid tuberosity of humerus) and from the midpoint of vertical length of deltoid muscle. The measurements were recorded and tabulated.

The measurements were entered in Microsoft excel and mean, proportion, standard deviation were calculated by using SPSS 16th version.

The axillary nerve was found to take origin from the posterior cord of brachial plexus (100%) dividing into anterior & posterior branches in Quadrangular space (88%) and supply deltoid muscle mainly. It also gave branches to teres minor muscle, shoulder joint capsule & superolateral brachial cutaneous nerve (100%). This study concluded that the mean distance of axillary nerve from the - anteromedial aspect of tip of coracoid process, posterolateral aspect of acromion process, midpoint of deltoid insertion & from the midpoint of vertical length of deltoid muscle measured to be (in cm) as 3.56±0.51, 7.4±0.99, 6.7±0.47 & 2.45±0.48 respectively. The mean vertical distance of entering point of axillary nerve from the anterior upper, mid middle upper & posterior upper deltoid border found to be (in cm): 4.94±0.86, 5.14±0.90 & 5.44±0.95 respectively and the horizontal anterior & horizontal posterior mean distance being 4.54±0.65 & 3.22±0.53 respectively. The mean height, mean width & mean depth of Quadrangular space measured to be (in cm): 2.23±0.40, 2.19±0.22 & 1.25±0.14 respectively.

The findings were found to be highly significant when males were compared with females but not significant when sides (right & left) were compared.