01Approach to the Critical Patient/attcp44

Immediate priorities

›Red flag recognition

›Complete deltoid paralysis with dense sensory loss

›Suggests axonotmesis or neurotmesis

›Urgent electrodiagnostic evaluation required

›Multiple nerve distributions involved

›Suggests brachial plexus injury

›Vascular compromise possible

›Penetrating trauma to the shoulder

›High suspicion for nerve transection

›Immediate surgical consultation

›Vascular emergency screen

›Diminished or absent distal pulses post-dislocation

›Axillary artery injury

›Expanding hematoma sign

›If vascular injury suspected, immediate vascular surgery consultation

›Do not delay for imaging if hard signs present

›Class I recommendation for emergent surgical management of vascular injury

Stabilization and initial assessment

›Initial priorities

›Dislocation reduction if present

›Prolonged dislocation associated with persistent motor weakness

›Procedural sedation as needed

›Neurovascular documentation pre- and post-reduction

›Motor function deltoid and teres minor

›Sensory function lateral deltoid patch

›Associated fracture assessment

›Proximal humerus fracture at surgical neck

02History/hx64

Mechanism and onset

›Traumatic mechanisms

›Anterior shoulder dislocation

›Most common cause of axillary nerve injury

›Nerve injury incidence 5% to 65% depending on detection method

›Proximal humerus fracture

›Especially surgical neck fractures

›Direct nerve contusion or traction

›Direct blow to deltoid region

›Contact sports tackle

›Football, rugby, wrestling, hockey

›Non-traumatic and insidious mechanisms

›Quadrilateral space syndrome

›Posterior shoulder pain with overhead activity

›Compression by fibrous bands or hypertrophied muscles

›Brachial neuritis (Parsonage-Turner syndrome)

›Acute severe shoulder pain preceding weakness

›Often atraumatic onset

›Iatrogenic

›Shoulder arthroplasty

›Arthroscopic procedures involving inferior capsule

Symptom characterization

›Motor symptoms

›Shoulder abduction weakness

›Inability to raise arm above 90 degrees

›Difficulty with overhead activities

›External rotation weakness

›Teres minor involvement

03Physical Exam/exam62

Inspection and general

›Deltoid assessment

›Lateral shoulder contour flattening

›Deltoid atrophy (may take weeks to appear)

›Bilateral comparison essential

›Arm position at rest

›Internal rotation posture

›Arm held close to body

Motor testing

›Deltoid strength testing

›Shoulder abduction against gravity

›All three heads of deltoid

›Grade 0 to 5 MRC scale

›Abduction in internal rotation test

›Most sensitive clinical test for axillary nerve palsy

›100% sensitivity in one validation study

›Deltoid extension lag test (swallowtail test)

›Posterior shoulder extension lag identifies posterior deltoid weakness

›Identified injury in 10 of 14 patients in validation study

›Teres minor testing

›External rotation resistance

›Weakness implicates posterior division of axillary nerve

›Compare bilaterally

›Hornblower sign

›Inability to externally rotate with elbow at shoulder height

›Also seen in infraspinatus tear

Sensory testing

›Lateral deltoid patch

04Differential Diagnosis/ddx54

Life-threatening and urgent

›Vascular injury

›Axillary artery injury

›ICD-10 S45.001 injury of axillary artery

›Hard signs include expanding hematoma and absent pulse

›Brachial artery injury

›Distal pulse deficit

›Urgent vascular surgery

›Brachial plexus injury

›Upper trunk injury (C5-C6)

›Broader deficits including supraspinatus and biceps

›Erb palsy pattern

›Infraclavicular brachial plexus lesion

›Multiple nerve distributions

›Higher energy mechanism required

Common mimics

›Rotator cuff pathology

›Full thickness rotator cuff tear

›Preserved sensation distinguishes from nerve injury

›Coexists with axillary nerve injury in up to 65% of dislocations

›Supraspinatus tendon tear

›Weakness in abduction

›No sensory deficit

›Cervical radiculopathy

›C5-C6 radiculopathy

›ICD-10 M54.12 radiculopathy cervical region

›Neck pain, biceps reflex loss, broader sensory distribution

›C5-C6 foraminal stenosis

05Laboratory Tests/lt41

Routine assessment

›Standard trauma labs

›Complete blood count

›Baseline in polytrauma

›Leukocytosis if infectious etiology considered

›Basic metabolic panel

›Renal function for medication dosing

›Glucose for neuropathy risk assessment

›Neuropathy screening when clinically indicated

›HbA1c

›Diabetic neuropathy contribution

›Target below 7% for nerve protection

›Vitamin B12 level

›Deficiency impairs nerve regeneration

›Especially in older patients or malnutrition

›TSH

›Hypothyroid neuropathy

›Underrecognized cause of peripheral nerve dysfunction

Inflammatory and autoimmune screen

›When brachial neuritis suspected

›ESR and CRP

›Elevated in inflammatory plexopathies

›Not specific but supports inflammatory etiology

›CBC for leukocytosis

›Infectious or inflammatory process

›Baseline for monitoring

›When vasculitis or autoimmune etiology suspected

›ANA

06Diagnostic Tests/dt92

Scoring Systems

›Seddon classification

›Neurapraxia

›Conduction block without axonal disruption

›Recovery within weeks to 3 months

›Axonotmesis

›Axonal disruption with intact endoneurium

›Recovery by axonal regrowth at 1 mm per day

›Neurotmesis

›Complete nerve disruption

›Surgical repair required for recovery

›Sunderland grading

›Grade 1 neurapraxia equivalent

›Full spontaneous recovery expected

›No EMG denervation

›Grades 2-4 axonotmesis spectrum

›Variable endoneurial and perineurial disruption

›Recovery less predictable as grade increases

›Grade 5 neurotmesis

›Complete nerve disruption

›Worst prognosis without surgery

›MRC muscle strength grading

›Grade 0 no contraction

›Complete paralysis

›Consistent with neurotmesis or severe axonotmesis

›Grade 3 movement against gravity

›Functional recovery threshold in many studies

›Surgical success often defined as achieving MRC 3 or above

›Grade 5 normal power

›Full recovery

›Expected in neurapraxia

MRI

›MRI shoulder indications

›Denervation signal detection

›Increased T2 signal in deltoid and teres minor

›Appears within weeks of injury

›Associated lesion identification

›Rotator cuff tears

›Labral pathology post-dislocation

›Nerve signal abnormality at quadrilateral space

›Correlates with poorer prognosis

›Identifies entrapment site

›MR neurography

›Gold standard for axillary nerve visualization

›Identifies hourglass constrictions

›Detects nerve discontinuity and perineural edema

›Indications

›Severe or unexplained weakness

›Pre-surgical planning

›No recovery by 3 months

›Timing

›Optimal after 6 to 8 weeks to allow edema evolution

›Immediate if vascular or structural emergency suspected

CT

›CT shoulder indications

›Bone injury assessment

›Proximal humerus fracture characterization

›Glenoid fracture evaluation

›Pre-operative planning

›3D reconstruction for complex fracture-dislocation

›Articular surface assessment

›CT angiography

›Vascular injury assessment

›Axillary artery injury post-dislocation

›Hemodynamically stable patients with hard signs

›Sensitivity and specificity

›High sensitivity for arterial injury detection

›Guides surgical planning

›Contraindications

›Contrast allergy

›Severe renal impairment

Ultrasound

›Point-of-care ultrasound

›Nerve caliber assessment

›Identifies entrapment sites along axillary nerve course

›Useful adjunct at point of care

›Hematoma identification

›Post-dislocation hematoma compressing nerve

›Guides aspiration or drainage decision

›Diagnostic ultrasound of peripheral nerve

›Axillary nerve visualization

›Quadrilateral space assessment

›Fibrous band detection

›Dynamic assessment

›Nerve movement with arm position

›Compression dynamic identification

›EMG and nerve conduction studies

›Primary confirmatory diagnostic test

›Baseline obtained within 4 weeks of injury

›Follow-up at 12 weeks

›EMG findings

›Fibrillation potentials and positive sharp waves in deltoid and teres minor

›Appear approximately 3 weeks post-injury

›NCS findings

›Reduced CMAP amplitude from Erb's point stimulation

›Greater than 40% CMAP asymmetry has 95% sensitivity and 97% specificity

07Disposition/dispo44

Emergency department disposition

›Discharge criteria

›Isolated axillary nerve injury after successful dislocation reduction

›Stable neurovascular exam post-reduction

›Adequate pain control achieved

›No associated vascular injury

›Intact distal pulses

›Normal capillary refill

›Reliable follow-up arranged

›Orthopedic or peripheral nerve clinic within 1 to 2 weeks

›EMG/NCS arranged for 4-week timeframe

›Admission indications

›Associated vascular injury

›Axillary artery disruption

›Expanding hematoma

›Irreducible dislocation

›Requires operative reduction

›Combined orthopedic and nerve injury management

›Polytrauma

›Additional injury management priorities

›Complex surgical planning

Follow-up planning

›Outpatient surveillance schedule

›Clinical reassessment at 2 to 4 weeks

›Motor and sensory function trend

›Pain management review

›EMG/NCS at 4 weeks (baseline)

›Establishes denervation extent

08Treatment/t96

Acute phase management (0 to 4 weeks)

›Immediate injury management

›Dislocation reduction

›Prompt reduction to minimize nerve stretch duration

›Procedural sedation agents as needed

›Fracture fixation planning

›Surgical neck fracture requires orthopedic consultation

›Timing coordinated with nerve recovery monitoring

›Immobilization

›Sling immobilization for comfort

›Limit duration to prevent shoulder contracture

›Analgesia

›NSAIDs

›Ibuprofen 400 to 600 mg orally every 6 to 8 hours

›Naproxen 500 mg orally every 12 hours

›Acetaminophen

›500 to 1000 mg orally every 6 hours

›Maximum 3000 mg per day in elderly

›Short-course opioids for severe acute pain

›Oxycodone 5 mg orally every 4 to 6 hours as needed

›Limit to 3 to 5 days in acute setting

Neuropathic pain management

›Gabapentinoids

›Gabapentin

›Start 100 to 300 mg orally at bedtime

›Titrate by 300 mg every 3 to 7 days

›Target 900 to 1800 mg per day in divided doses

›Pregabalin

›Start 75 mg orally twice daily

›Titrate to 150 to 300 mg twice daily

›Renal dose adjustment required if creatinine clearance below 60 ml per minute

›Antidepressants for neuropathic pain

›Amitriptyline

›10 to 25 mg orally at bedtime

›Titrate slowly over weeks

›Use with caution in elderly due to anticholinergic effects

›Duloxetine

›30 mg orally daily for 1 week then 60 mg daily

›Evidence base for neuropathic pain (Class IIa)

Rehabilitation phase (4 weeks onward)

›Physical therapy program

›Passive and active-assisted ROM

›Prevent shoulder contracture

›Loss of mobility permanently affects outcome even if nerve recovers

›Progressive strengthening

›Rotator cuff, deltoid, and periscapular musculature

›As reinnervation progresses

›Functional activity retraining

›Return to overhead activities

›Sport-specific rehabilitation when applicable

›Serial monitoring

›Clinical assessment every 4 to 6 weeks

›Motor function trends

›Sensory recovery mapping

›EMG/NCS at 12 weeks

›Reinnervation evidence evaluation

›Guides decision for surgical referral

Surgical management

›Indications

›No clinical or electrophysiologic recovery by 3 to 4 months

›Class IIa recommendation based on expert consensus

›Best outcomes when surgery performed within 3 to 6 months of injury

›High-energy trauma or penetrating injury at presentation

›Early exploration may be indicated

›Suspected neurotmesis pattern

›Surgical options

›Neurolysis

›For nerve-in-continuity lesions

›Removes scar tissue compressing viable nerve

›Nerve grafting

›Sural nerve graft for nerve gaps

›Average MRC grade 4.3 achieved in one series

›Nerve transfer (triceps motor branch to axillary nerve)

›Increasingly preferred technique

›87.6% of isolated axillary nerve injury patients achieved MRC grade 3 or above

›All patients regained 90 degrees or greater abduction in one series

›Neurotization options

›Triceps branch transfer: 80% success rate

›Subscapular nerve transfer: 79% success rate

›Fascicle transfer from ulnar or median nerve: 74% success rate

›Data from 206-patient series

›Factors affecting surgical outcome

›Delay from injury to surgery (most important prognostic factor)

›Earlier intervention improves outcomes

›Beyond 6 months success rates decline

›Patient age

›Younger patients have greater regenerative capacity

›Older age associated with poorer outcomes

›BMI

›Higher BMI associated with worse outcomes

›Mechanism unclear but may relate to nerve length requirements

Brachial neuritis management

›Parsonage-Turner syndrome

›Corticosteroids

›May reduce duration of acute pain phase

›Evidence limited (Level C recommendation)

›Prednisone 60 to 80 mg orally daily for 10 days then taper

›Supportive care

›Pain control priority in acute phase

›Shoulder sling for comfort

›Recovery typically over months

09Special Populations/sp76

Pregnancy

›Pregnancy-specific considerations

›Mechanism differences

›Axillary nerve injury less common as isolated traumatic event

›Positioning-related stretch during labor or delivery rare but reported

›Imaging approach

›MRI without gadolinium preferred in first trimester

›Gadolinium contraindicated in pregnancy unless benefits clearly outweigh risks

›Medication safety

›Acetaminophen preferred first-line analgesic

›NSAIDs avoid after 20 weeks gestation

›Gabapentin: FDA Category C, use with caution

›Amitriptyline: relatively contraindicated in third trimester

›Surgical timing

›Defer elective nerve surgery until postpartum when possible

›Emergency intervention for vascular injury proceeds regardless

›Anesthesia risk-benefit discussion required

Geriatric

›Age-related considerations

›Higher incidence of nerve injury with glenohumeral dislocation

›More common in patients 60 years and older

›Associated with greater energy required for re-dislocation

›Poorer nerve regeneration capacity

›Recovery timeline extended

›Lower rate of full functional recovery

›Rotator cuff tear coexistence

›Very high prevalence in older patients with dislocation

›Both conditions may coexist and require separate investigation

10Background/b75

Epidemiology

›Incidence and prevalence

›Most common peripheral nerve injury of the shoulder

›Axillary nerve most frequently injured nerve after glenohumeral dislocation

›Reported incidence 5% to 65% after anterior shoulder dislocation depending on detection method

›Glenohumeral dislocation association

›Anterior dislocation accounts for 90% to 95% of all shoulder dislocations

›Nerve injury frequency underdiagnosed due to clinical detection limitations

›Iatrogenic incidence

›Shoulder arthroplasty nerve injury rate 0.7% to 4%

›Axillary nerve most commonly affected in arthroplasty series

›Demographics and risk

›Bimodal age distribution

›Young athletes (contact sports) and older patients (low energy falls)

›Older patients have higher nerve injury rate and worse recovery

›Sex distribution

›Male predominance in traumatic mechanism group

›Sport-related injuries predominantly male

›Recovery statistics

›Majority recover with nonoperative treatment

›20% to 30% of axonotmetic injuries may have incomplete recovery

Pathophysiology

›Anatomic vulnerability

›Axillary nerve origin

›C5-C6 nerve roots

›Posterior cord of brachial plexus

›Quadrilateral space traversal

›Bounded by teres minor superiorly, teres major inferiorly, long head triceps medially, surgical neck humerus laterally

›Fixed anatomical tunnel creates compression risk

›Surgical neck wrapping

›Nerve wraps around surgical neck of humerus

›Tethered position limits mobility during joint displacement

›Injury mechanisms

›Traction injury

›Inferior humeral displacement stretches nerve

›Most common mechanism in anterior dislocation

›Direct contusion

›Proximal humerus fracture fragment

›Direct deltoid impact

›Compression entrapment

›Quadrilateral space syndrome

›Fibrous bands or hypertrophied teres minor

›Nerve injury spectrum

›Neurapraxia

›Focal demyelination without axonal loss

›Conduction block resolves with remyelination

›Axonotmesis

›Axonal disruption with intact connective tissue framework

›Wallerian degeneration distal to injury

›Axonal regeneration at approximately 1 mm per day

›Neurotmesis

›Complete nerve disruption

›No spontaneous functional recovery without surgical repair

Therapeutic Considerations

›Conservative management rationale

›Most injuries are neurapraxic or mild axonotmetic

›Spontaneous recovery expected

›No specific pharmacologic intervention accelerates nerve regeneration

›Rehabilitation prevents secondary complications

›Shoulder contracture is preventable

›Muscle atrophy minimized with active engagement

›Electrodiagnostic timing

›EMG optimal after 3 to 4 weeks

›Fibrillation potentials require this interval to appear

›Early EMG may underestimate severity

›Repeat at 12 weeks critical decision point

›Reinnervation potentials guide surgical decision

›Absence of voluntary MUAPs is concerning

›Surgical decision framework

›Time-sensitive intervention window

›Surgical outcomes best within 3 to 6 months

›Muscle fibrosis beyond this window reduces benefit

›Nerve transfer advantages over grafting

›Shorter reinnervation distance with triceps branch transfer

›Avoids donor site morbidity of sural nerve harvest in selected cases

›Evidence base

›Nerve transfer achieves MRC 3 or above in approximately 88% of isolated cases

›Sural nerve grafting achieves average MRC 4.3 in comparable series

11Patient Discharge Instructions/pdi52

copy discharge instructions

›What happened and what to expect

›Axillary nerve injury diagnosis explained

›The nerve controlling shoulder muscles was injured

›Most people recover with time and rehabilitation

›Recovery timeline

›Mild injuries recover within weeks to 3 months

›More severe injuries may take 6 to 12 months

›Regular follow-up appointments are essential to track recovery

›Home care instructions

›Sling use

›Wear sling as directed for comfort

›Remove for gentle exercises as instructed by physiotherapist

›Medications

›Take pain medications as prescribed

›Complete any prescribed medication courses

›Exercise instructions

›Perform only exercises taught by physiotherapist

›Gentle pendulum exercises help prevent shoulder stiffness

›Do not lift heavy objects until cleared by your doctor

›Warning signs to return to emergency

›New or worsening weakness in the arm or hand

›Inability to move fingers or elbow

›Rapid change in function

›Arm or hand becomes cool, pale, or blue

›Blood vessel injury possible

›Emergency assessment required immediately

›Severe or uncontrolled pain not responding to medications

12References/r40

Guidelines and key sources

›Primary clinical guidelines

›Perlmutter GS - Axillary Nerve Injury - Clinical Orthopaedics and Related Research 1999

›Foundational reference for mechanism, diagnosis, and management

›PMID 10613150

›Steinmann SP, Moran EA - Axillary Nerve Injury Diagnosis and Treatment - JAAOS 2001

›Comprehensive clinical management review

›PMID 11575912

›Hagert E, Hagert CG - Upper Extremity Nerve Entrapments Axillary and Radial Nerves - PRS 2014

›Surgical anatomy and treatment options

›PMID 24622568

›Surgical outcomes evidence

›Lee JY et al - Factors Affecting Outcome of Triceps Motor Branch Transfer - Journal of Hand Surgery 2012

›Nerve transfer outcomes analysis

›PMID 23044480

›Baltzer HL et al - Comparison of Outcomes Triceps Motor Branch vs Sural Nerve Grafting - PRS 2016

›Comparative surgical technique outcomes

›PMID 27465187

›Haninec P et al - Nerve Transfers for Axillary Nerve Repair - Journal of Neurosurgery Spine 2025

›Largest series with 206 patients

›PMID 40053939

›Diagnostic studies

›Bertelli JA, Ghizoni MF - Abduction in Internal Rotation Test - Journal of Hand Surgery 2011

›Clinical test validation for axillary nerve palsy

›PMID 22051233

›Lui I et al - MRI Features of Axillary Nerve Injuries Following Glenohumeral Dislocation - Skeletal Radiology 2025

›MRI diagnostic criteria

›PMID 41145831

Evidence & Review