INTRODUCTION:: The aim of this study is to quantify the length of the axillary nerve (AN) that is able to be dissected through a standard anterior (deltopectoral) and posterior approach. We hypothesize that a segment of the AN cannot be reached using both approaches simultaneously. MATERIAL AND METHODS:: ANs of 5 frozen cadavers were dissected using an anterior and posterior approach. A first surgical clip marked the most visible distal part of the nerve from the deltopectoral approach; a second surgical clip marked the most proximal part from the posterior approach. The two surgical clips were localized with a shoulder radiograph. We performed measurements of the different AN segments. RESULTS:: In all specimens there were three zones of the AN. Zone A (anterior): nerve segment from the origin of the AN to the first surgical clip, located at the level of the triangle formed by the subscapularis muscle (medial), conjoined tendon (lateral) and axillary fat (inferior). Zone B (blind – nerve segment not reachable through both approaches): from the first to the second surgical clip. Zone C (circumflex): nerve segment from the second surgical clip (located at the level of the quadrilateral space) to entry into the deltoid muscle. The mean length of the blind zone was 1.6 cm. This blind zone was found 1-2 cm. to the glenohumeral joint. CONCLUSIONS:: We have described a segment of the AN that cannot be evaluated through anterior (deltopectoral) and posterior combined approaches. An AN classification is presented based on the possible injured segment. We believe that this finding is important for the surgical evaluation of AN injuries around the quadrilateral space.
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