Axillary Nerve Lesions

Anatomy

 

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

 

Aetiology

 

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

 

Mechanism

- Compression in position ER and abduction

 

Symptoms

- get pain and paraesthesia in shoulder 

- can have chronic dull ache

 

Signs

- usually no deltoid atrophy or sensory changes

 

Investigation

 

EMG

- normal

 

Angiogram

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

 

MRI

- may shows changes in deltoid and Tm

 

Mangement

- 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

 

Management

- can treat with steroids

- usually good prognosis

 

5.  Nerve compression from mass effect

 

Cause

- aneurysm, tumour

 

History

 

No history trauma

- suspect mass effect / quadrilateral space syndrome / brachial neuritis

 

Pain then loss of function

- suspect brachial neuritis

 

History dislocation

 

Examination

 

Deltoid Wasting

 

Wasting Deltoid

 

Weakness of shoulder abduction

 

Numbness in Regimental patch 

- variable

 

DDx

 

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

- SSC

 

NCS / EMG

 

Diagnose higher lesion

- reference point for recovery

 

MRI

 

Mass lesions

Atrophy of T minor

Assess RC 

 

Operative Management

 

Indications

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

- open wounds / stab wounds

 

Timing

 

Best results 

- reinnervation must occur before one year

- otherwise get degeneration of NMJ

- i.e. surgery must occur by 9 months

 

Options

 

No muscle transfer for deltoid

- nerve repair

- neurolysis

- nerve grafting

- nerve transfer

 

1.  Neurolysis

 

Indications

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

 

Technique

- identify nerve

- use nerve stimulator intra-operatively

- stimulation of nerve will cause muscle contraction if intact

- uncommon

 

2.  Neurorrhaphy 

 

Indication

- laceration

 

Technique

- direct repair of laceration

- if in first few weeks

 

3.  Nerve grafting

 

Indications

- 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

 

Results

 

Allnot Int Orthop 1991

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

 

4.  Neurotisation / Nerve transfer

 

Concept

- use branch of radial nerve

- transfer into motor branch axillary

- single incision

 

Technique

- 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

 

Results

 

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