title: The posterior branch of the axillary nerve: an anatomic study.
abstract: BACKGROUND
  Surgery on the posterior aspect of the shoulder has become accepted practice for a number of pathological conditions affecting the scapula and the glenohumeral joint. Despite this trend, the anatomy of the posterior branch of the axillary nerve has not been well characterized. The purpose of the present study was to determine the innervation pattern and surgical relationships of the posterior branch of the axillary nerve.
  
  
  METHODS
  Nineteen fresh-frozen human cadaveric forequarter amputation specimens were dissected through a posterior approach. The location of the posterior branch of the axillary nerve and its anatomical relationships with surrounding structures were documented and measured with use of digital calipers.
  
  
  RESULTS
  The posterior branch separated from the main anterior circumflex branch of the axillary nerve immediately anterior to the origin of the long head of the triceps muscle at the six o'clock position on the glenoid. It coursed posteriorly, adjacent to the inferior aspect of the glenoid rim for an average distance of 10 mm (range, 2 to 17 mm) before dividing into the superior-lateral brachial cutaneous nerve and the nerve to the teres minor. The nerve to the teres minor coursed medially along the posterior aspect of the inferior part of the glenoid rim for an average distance of 18 mm (range, 11 to 25 mm) before entering the muscle at its inferior border. The superior-lateral brachial cutaneous nerve coursed inferiorly, deep to the posterior aspect of the deltoid. It became superficial by passing around the medial border of the muscle at an average of 8.7 cm (range, 6.3 to 10.9 cm) inferior to the posterolateral corner of the acromion.
  
  
  CONCLUSIONS
  The posterior branch of the axillary nerve has an intimate association with the inferior aspects of the glenoid and shoulder joint capsule, which may place it at particular risk during capsular plication or thermal shrinkage procedures. The superior-lateral brachial cutaneous nerve and the nerve to the teres minor always arise from the posterior branch. Thus, loss of sensation over the deltoid may indicate loss of teres minor function. The posterior aspect of the deltoid has a more consistent supply from the anterior branch of the axillary nerve, necessitating caution when performing a posterior deltoid-splitting approach to the shoulder.
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, Missouri 63110, USA.
authors.forename: Craig M
authors.initials: CM
authors.lastname: Ball
authors.forename: Thomas
authors.initials: T
authors.lastname: Steger
authors.forename: Leesa M
authors.initials: LM
authors.lastname: Galatz
authors.forename: Ken
authors.initials: K
authors.lastname: Yamaguchi
mesh_terms: D000328:Adult; D001365:Axilla / Q000294:innervation*; D006801:Humans; D007592:Joint Diseases / Q000473:pathology / Q000601:surgery*; D018482:Muscle, Skeletal / Q000294:innervation / Q000601:surgery; D010525:Peripheral Nerves / Q000473:pathology* / Q000601:surgery; D012016:Reference Values; D012785:Shoulder Joint / Q000294:innervation* / Q000601:surgery