Axillary nerve injury: Current concept review

Devon Patel; Vanessa Shannon; Zialesi Adissem; James Bassett; Nabil Ebraheim

doi:10.1016/j.jorep.2022.100050

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Review Article

2022

:1;

100050

doi:

10.1016/j.jorep.2022.100050

Axillary nerve injury: Current concept review

Devon Patel^a,, Vanessa Shannon^a, Zialesi Adissem^a, James Bassett^a, Nabil Ebraheim^b

a The University of Toledo College of Medicine and Life Sciences, 3000 Arlington Avenue, Toledo, OH, 43614, USA

b University of Toledo Medical Center, Department of Orthopaedics, 1125 Hospital Drive, Toledo, OH, 43614, USA

∗Corresponding author: Devon Patel. Devon.Patel@rockets.utoledo.edu

Received: 2022-6-17, Accepted: 2022-6-23, Published: 2022-6-28

The Author(s)

Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

The axillary nerve is the most commonly injured nerve in the shoulder and is particularly susceptible to injury due to its anatomical relation in the quadrangular space on the posterior scapula.

This review aimed to provide an updated summary of various injuries to the axillary nerve and its management.

PubMed, Embase, and Google Scholar were searched for articles published in the English language pertaining to axillary nerve anatomy, injury, and treatment. Articles published between 1960 and May 2022 were included.

The axillary nerve is often injured after shoulder dislocations or humeral fractures and can heal without surgical intervention. Operative treatments are indicated if the injury does not show signs of recovery.

Injuries to the axillary nerve are commonly encountered and it is imperative for providers to know how to effectively treat patients with these conditions. After a thorough physical exam and determining the diagnosis of axillary nerve injury, patients should undergo physical therapy to restrengthen affected musculature and range of motion. If conservative methods are unsuccessful, surgical interventions such as neurolysis or nerve transfer could be indicated.

Keywords

Axillary nerve

Axillary nerve injury

Glenohumeral joint

Shoulder dislocation

Brachial plexus

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1 Introduction

Injury to the axillary nerve is the most common peripheral nerve injury of the shoulder and commonly arises from glenohumeral joint dislocation, humerus fracture, or direct trauma to the deltoid muscle.¹ Due to the location of the axillary nerve, injury can also be a result of various types of compression to the nerve.¹ While these compressions are uncommon they are very debilitating.² Some common causes of non-traumatic compression injuries to the axillary nerve are quadrilateral space syndrome and improper crutches use.²^,³ The anatomical complexity and anomalies of the axillary nerve create a significant potential for injury and treatment is both nonoperative and operative. With surgical treatment, a delay of more than 6 months between trauma to the axillary nerve and surgical intervention is not ideal, although various surgical procedures have shown successful outcomes.⁴

2 Methods

PubMed, Embase, and Google Scholar were searched for articles published between 1960 and May 2022 in the English language. Articles were also found by analyzing the reference lists of studies from the database search. The keywords “axillary nerve”, “axillary nerve anatomy”, “axillary nerve injury”, “axillary nerve dysfunction”, and “axillary nerve injury treatment” were used to find relevant articles.

3 Discussion

3.1

3.1 Anatomy

The axillary nerve arises from the posterior cord of the brachial plexus and receives fibers from the C5 and C6 nerve roots (Fig. 1). The axillary nerve travels in the superior portion of the quadrangular space along with the posterior humeral circumflex artery around the surgical neck of the humerus (Figs. 2–3).⁵ This anatomic relation also serves as a potential source of entrapment and nerve pathology. The axillary nerve provides motor innervation to the deltoid and teres minor muscles and sensory innervation to the skin over the inferior deltoid (the “regimental badge area”) via its anterior and posterior branches (Figs. 4–5).⁶^,⁷

The brachial plexus arises from the C5-T1 ventral rami to provide motor and sensation input to the upper extremities and some axial muscles. The axillary nerve is a continuation of the posterior cord.

The axillary nerve travels around the surgical neck of the humerus and then branches into its anterior and posterior divisions.

The axillary nerve passes posteriorly through the quadrangular space. The quadrangular space is bordered by the teres minor (superiorly), teres major (inferiorly), long head of the triceps (medially), and humeral shaft (laterally).

A) The anterior and posterior division of the axillary nerve supply the anterior and posterior deltoid, respectively, to aid in shoulder abduction. B) The posterior division provides motor innervation to the teres minor to stabilize the glenohumeral joint and aid in external rotation.

The axillary nerve bifurcates into an anterior division (motor supply to the anterior deltoid and sensory supply to the anterior and anterolateral shoulder) and posterior division (motor supply to posterior deltoid and teres minor). Note the posterior division continues into the upper lateral cutaneous nerve of the arm.

In a cadaveric study, the axillary nerve enters the deltoid muscle approximately 5 cm from the humeral head and has an average diameter of 0.57 cm.⁸ The anterior and posterior branches have smaller diameters, 0.40 cm, and 0.33 cm, respectively.⁸ There are also significant differences in anatomical locations between males and females. Male cadavers have greater distances between the axillary nerve and posterior corner of the acromion and the axillary nerve and midportion of the acromion than females.⁹ Although the axillary nerve commonly arises from the posterior cord of the brachial plexus, it can arise from the posterior division of the upper trunk in 20% of patients.¹⁰

3.2

3.2 Clinical presentation and diagnosis

Axillary nerve injuries often occur due to tractional injuries involving the shoulder region and in combination with other brachial plexus damages.¹¹ The deltoid muscle is most commonly involved in these contact injuries, though the remaining rotator muscles may also be involved.¹² Though most axillary nerve injuries are due to direct and indirect contact from high-energy and low-energy trauma in this region, some cases arise with no apparent trauma at the source. Termed brachial neuritis, this pain may cause pain and interference in the axillary nerve region. Such is the case in prolonged crutches use which applies a horizontal pressure to the axillary nerve and other axilla region structures causing numbness and tingling, an indication of injury to the nerve.³ It generally has shorter healing progress and more successful outcomes compared to other axillary nerve injuries.¹¹ Diagnosis usually follows after the collection of the patient's clinical history to identify trauma, as well as a physical exam that evaluates both active and passive motion of the rotator cuff muscles and shoulder. Muscle wasting and atrophy should also be assessed in the event of a chronic axillary nerve issue.¹¹

3.3

3.3 Treatment/complications

Axillary nerve injury caused by glenohumeral joint dislocation or humerus fracture has a good prognosis for functional recovery without operative management. Early physical therapy focused on range of motion (ROM) and maintaining strength is indicated to reduce atrophy of the deltoid during axillary nerve recovery.¹³ Recovery should be monitored with electromyogram and nerve conduction studies (EMG/NCS) routinely, starting at 2–4 weeks to determine the reinnervation of the deltoid.¹⁴ In one case study, a 27-year-old professional rugby player with a Sunderland grade III-IV re-injury returned to sports after 2 months of conservative treatment.¹⁵

Injuries with no sign of recovery by 3 months are indicative of a more severe axillary nerve injury where surgical intervention may be considered. Significant improvement in the patient outcome results from operations taking place within 12 months of the onset of injury.¹⁰ Surgical interventions include neurolysis, nerve graft, nerve transfer, and tendon transfer. Radial nerve transfers within 6 months of injury to the axillary nerve show significant improvement in range of motion within the shoulder and when applicable, long-nerve grafts can be equally as effective as nerve transfers.¹⁶^,¹⁷ In the case of neglected axillary nerve injuries, a tendon transfer from the trapezius to the proximal humerus was shown to increase shoulder stabilization and restore the ROM of abduction to a mean of 78°.¹⁸ In the general population ROM of shoulder abduction is approximately 150° at baseline.¹⁹ Furthermore, sural nerve allografts approximately 10 months after the sustained injury have shown satisfactory results in deltoid function and ROM in delayed axillary nerve injuries.⁴

4 Conclusion

Axillary nerve injuries are the most common peripheral nerve injury of the shoulder. Due to the nerve's anatomical relationship to the humerus and quadrangular space, injuries that occur in contact injuries result in shoulder dislocation, humerus fracture, or direct trauma to the deltoid. Diagnosis can typically be achieved through a patient history and physical examination of the rotator cuff ROM. Muscle wasting and atrophy can be an indication of a chronic nerve issue. Many axillary nerve injuries result in full recovery with conservative treatment and monitoring. No signs of recovery after 3 months of EMG/NCS tests are indicative of surgical intervention.

Funding

This review did not receive any funding or other support.

Authors contribution

All authors analyzed the data and wrote the manuscript; all authors have read and approved the final manuscript.

Institutional ethical committee

The current study did not involve human participants and did not require ethical committee approval for the literature review.

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