Axillary Nerve Lesions



Terminal branch of the posterior cord

- lateral to radial nerve

- behind axillary artery

- runs over inferolateral border of SSC

- enters quadrangular space


Quadrangular space

- SSC superiorly anterior

- T major inferior

- T minor superiorly posterior

- long head triceps and humerus


Divides into anterior and posterior branches


Axillary Nerve Sagittal MRI 1Axillary Nerve Sagittal MRI 2


Anterior branch

- curves around SNOH

- deep to deltoid

- 4-7 cm inferior to corner acromion

- supplies anterior and middle portions deltoid


Posterior branch

- supplies T minor and posterior deltoid

- sensory branch


3 distinct fascicles

- T minor

- deltoid (supero-lateral)

- superior lateral cutaneous branch




1.  Traumatic

2.  Iatrogenic

3.  Quadrilateral Space Syndrome

4.  Brachial Neuritis

5.  SOL


1.  Traumatic


A. Shoulder Dislocation

- 10-20% incidence post dislocation


Blom et al Acta Chir Scand 1970

- 9 complete and 15 partial lesions

- all recovered within 1 - 2 years


Gumina JBJS Br 1997

- high rate in elderly > 40 (50%)

- all recovered by 3 years

- high rate of RC (20%)


B. Proximal Humeral fracture


C. Brachial Plexus injury

- rarely isolated

- in conjunction with other injuries

- upper trunk


D.  Blunt trauma to deltoid


2.  Surgery


A.  Deltoid-Splitting approach

- lies 5cm lateral to anterolateral corner of acromion


B.  Deltopectoral approach

- undue care at inferior level of SSC


3. Quadrilateral space syndrome



- Compression in position ER and abduction



- get pain and paraesthesia in shoulder 

- can have chronic dull ache



- usually no deltoid atrophy or sensory changes





- normal



- shows compression of posterior humeral circumflex artery with less than 60o abduction



- may shows changes in deltoid and Tm



- usually just observation

- occasionally need to decompress scar tissue or fibrous band


4.  Parsonage-Turner Syndrome


Brachial neuritis

- spontaneous development severe shoulder pain

- then develop loss of motor function

- usually also LTN, SS nerve, but occasionally isolated



- can treat with steroids

- usually good prognosis


5.  Nerve compression from mass effect



- aneurysm, tumour




No history trauma

- suspect mass effect / quadrilateral space syndrome / brachial neuritis


Pain then loss of function

- suspect brachial neuritis


History dislocation




Deltoid Wasting


Wasting Deltoid


Weakness of shoulder abduction


Numbness in Regimental patch 

- variable




1.  Upper trunk injury / root injury (C5/6)

- will also have injuries to


A.  SS nerve

- IS / SS

- remember dislocation may cause RC tear


B.  Subscapularis


C.  Biceps


2.  Posterior cord injury

- will also have injuries to


A.  Radial nerve

- triceps, WE, FE, thumb extension


B.  Thoracodorsal

- Lat Dorsi


C.  Upper and lower subscapular





Diagnose higher lesion

- reference point for recovery




Mass lesions

Atrophy of T minor

Assess RC 


Operative Management



- no clinical or NCS / EMG sign of recovery at 6/12

- open wounds / stab wounds




Best results 

- reinnervation must occur before one year

- otherwise get degeneration of NMJ

- i.e. surgery must occur by 9 months




No muscle transfer for deltoid

- nerve repair

- neurolysis

- nerve grafting

- nerve transfer


1.  Neurolysis



- if nerve intact but encased in scar or compressed by fibrous bands



- identify nerve

- use nerve stimulator intra-operatively

- stimulation of nerve will cause muscle contraction if intact

- uncommon


2.  Neurorrhaphy 



- laceration



- direct repair of laceration

- if in first few weeks


3.  Nerve grafting



- neuroma usually at or in quadrilateral space


2 Incision Technique


Sural nerve graft

- anastomose anteriorly, then pass through

- anastomose posteriorly


Lateral decubitus

- access anterior and posterior shoulder

- allows sural nerve harvest


Deltopectoral approach

- release half or all of P major (leave cuff for repair)

- must release conjoint tendon and P minor

- do so 1cm from origin

- expose axillary, radial and MCN

- use nerve stimulator to ensure nerve not working

- identify and protect axillary artery and vein

- if deltoid active, neurolysis


Identify neuroma

- if deep

- posterior approach to shoulder


Posterior vertical incision

- lateral border acromion to posterior axillary crease

- mobilise inferior border deltoid superiorly

- find nerve as exits quadrilateral space

- identify deltoid fascicle using nerve stimulator




Allnot Int Orthop 1991

- 23/25 isolated sural nerve grafting achieved M4 or M5 strength


4.  Neurotisation / Nerve transfer



- use branch of radial nerve

- transfer into motor branch axillary

- single incision



- posterior longitudinal approach to arm

- find AXN under wasted deltoid, exiting above T Major

- identify anterior branch of AXN going into muscle

- ensure not branch to T minor or sensory branch

- develop interval between long and lateral heads

- find radial nerve in groove between medial and lateral heads

- will be exiting below T Major between long and humerus

- harvest branch to long or medial head triceps

- long may be better as has two sources nerve supply and less functional impairment

- check with nerve stimulator

- repair with 9.0 nylon under microscope




Leechavengvongs et al J Hand Surg Am 2003

- all 7 patients had M4 power

- 5 excellent and 2 good results

- no demonstrable loss of elbow extension power