Axillary Nerve Injury

By admin On Nov 24, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Laura Distel

James R. Borchers

Basics

Originates from the C5–6 rami (and occassionally C4) and is a branch of the posterior cord of the brachial plexus (1)
Courses from the brachial plexus and below the coracoid process along the anterior surface of the subscapularis and then heads posteriorly and through the quadrilateral space (1)
The quadrilateral space is an anatomic entity created by the teres minor muscle inferiorly, the long head of the triceps medially, the neck of the humerus laterally, and the subscapularis and teres major muscles superiorly. The axillary nerve and posterior humeral circumflex artery travel within the space (1).
Once through the space, the nerve travels further posteriorly and branches into an anterior and posterior trunk.
The anterior trunk courses around the posterolateral (surgical) neck of the humerus and innervates the anterior and middle deltoid.
The posterior trunk bifurcates into a motor branch, the teres minor and posterior deltoid muscles, and a sensory branch innervating the superolateral brachial cutaneous nerve, which innervates the lateral upper extremity.

Epidemiology

Has been reported to encompass <1% of all nerve injuries (2)

Incidence

True incidence unknown owing to underrecognition of the diagnosis.

Risk Factors

Anterior shoulder (glenohumeral) dislocation
Humeral neck fracture
Direct blunt trauma to the anterior lateral deltoid, which is common in contact sports such as hockey, football, or rugby
Repetitive overhead sports (eg, volleyball, tennis, or baseball): This can lead to quadrilateral space syndrome.
Iatrogenic damage (eg, shoulder instability surgery, rotator cuff surgery, and rarely, shoulder arthroscopy)

Etiology

Traction injury to the nerve during an anterior dislocation or fracture (2)
Presumed compression injury of the nerve as a result of a direct blow to the anterolateral deltoid (2)
Quadrilateral space syndrome: Proposed mechanisms include compression of the nerve by fibrous bands, hypertrophied muscles that border the space, any space-occupying lesion (eg, aneurysm or cyst), or shear between the teres minor and major (2).
Iatrogenic damage to the nerve during shoulder surgery (2)

Commonly Associated Conditions

Anterior glenohumeral dislocation
Humeral neck fracture

Diagnosis

Nerve injury should be suspected in any athlete with anterior shoulder dislocation or humeral neck fracture.

History

Easy fatigability with overhead activities or heavy lifting (3)
Decreased strength with shoulder abduction (3)
Paresthesias or loss of sensation in the lateral upper arm (sensation is spared after anterior shoulder dislocation)
Quadrilateral space syndrome: Vague, nonspecific aching or burning of the posterolateral shoulder and/or generalized weakness with overhead activities (1)

Physical Exam

Assess for deltoid or teres minor atrophy compared with the unaffected side (more common in chronic cases).
Active and passive range of motion (ROM) about the shoulder, including abduction, forward elevation, and external rotation
Strength testing of abduction and forward elevation (deltoid function) and external rotation (teres minor function)
Neurovascular exam, especially assessing for sensation over the lateral deltoid area known as the “sergeant's patch”
Perform the Spurling maneuver (rotate the patient's head to the affected side and hyperextend the neck) to assess for cervical radiculopathy.
Tenderness to palpation of the posterior shoulder at the quadrilateral space (often the only positive finding in quadrilateral space syndrome)

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Diagnostic Tests & Interpretation

Imaging

Plain x-rays of the shoulder to evaluate glenohumeral dislocation or evidence of fracture (3)
Consider cervical spine x-rays to rule out cervical spine causes of deltoid paresthesias, weakness, or atrophy (1).
MRI can be helpful in chronic cases to identify a combined nerve injury, to determine prognosis of functional recovery by evaluating fatty replacement of the muscle, or to evaluate other soft tissue causes of shoulder weakness but is often not needed (3).

Diagnostic Procedures/Surgery

Electromyography (EMG) and nerve conduction velocity (NCV) should be obtained no sooner than 3 wks after injury to establish baseline dysfunction (3)[A].
Repeat EMG and NCV after 3 mos if no clinical improvement to assess for nerve recovery (2)[A].
Arteriogram of the posterior circumflex humeral artery to evaluate for quadrilateral space syndrome, but there are conflicting recommendations regarding the use of this test (1)[B].

Differential Diagnosis

Brachial plexus syndromes:
- Thoracic outlet syndrome
- Neuralgic amyotrophy (Parsonage-Turner syndrome)
Quadrilateral space syndrome
Cervical spine lesions
Aneurysm, neoplasm, or cystic mass near the axillary nerve

Treatment

Nonoperative treatment is preferred initially (2)[A].
Emphasize active and passive ROM of the shoulder.
Relative rest
Strengthening exercises of the shoulder
Avoidance of exacerbating triggers or activities

ED Treatment

Reduction of glenohumeral dislocation or treatment of fracture

Additional Treatment

Additional Therapies

Electrical stimulation of the deltoid is an option to prevent atrophy while the nerve is recovering (3)[C].

Surgery/Other Procedures

Appropriate interval for surgical intervention is unclear, but there is some evidence to suggest that surgery within 6 mos of injury yields superior return of function and strength (3)[B].
Generally indicated if no improvement using nonoperative treatments or if EMG/NCV shows no interval nerve recovery in 3–12 mos postinjury (2)[A]
Operative procedures include (2)[A]:
- Neurolysis
- Sural nerve grafting
- Neurorrhaphy
- Nerve transfer
- Neurotization
Surgical decompression can be performed for quadrilateral space syndrome to release fibrous bands (3)[B].

Ongoing Care

Follow-Up Recommendations

Routine clinical follow-up every 4–8 wks while patient is undergoing therapy to assess for return of strength and sensation
Repeat EMG/NCV if no improvement in 3 mos
Return to contact sports once full ROM and adequate strength of the shoulder are achieved.

Prognosis

Depends on mechanism and severity of nerve damage
Functional shoulder recovery is usually excellent (2).
85–100% of axillary nerve injury owing to fracture or dislocation will recover fully by 6–12 mos with nonoperative treatment (1).
Poorer prognosis for functional recovery in symptomatic patients who undergo surgical intervention >12 mos after date of injury (3)

References

1. Safran MR. Nerve injury about the shoulder in athletes, part 1: suprascapular nerve and axillary nerve. Am J Sports Med. 2004;32:803–819.

2. Perlmutter GS, Apruzzese W. Axillary nerve injuries in contact sports: recommendations for treatment and rehabilitation. Sports Med. 1998;26:351–361.

3. Steinmann SP, Moran EA. Axillary nerve injury: diagnosis and treatment. J Am Acad Orthop Surg. 2001;9:328–335.

Codes

ICD9

955.0 Injury to axillary nerve