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Axillary Palsy and Atony

Justin J. Mitchell, MD Abstract » palsy presents in a variety of ways and can be a Christopher Chen, MD substantial source of dysfunction about the shoulder. It is important for Daniel J. Liechti, MD the orthopaedic surgeon to recognize axillary nerve in the setting of acute trauma. The surgeon should also be aware that such Austin Heare, MD injuries are part of the complication profile of both open and Jorge Chahla, MD arthroscopic involving the shoulder.

Jonathan T. Bravman, MD » Early recognition and treatment is important as full recovery becomes less likely in association with chronic axillary nerve injuries. However, diagnosis is often difficult and can be masked by compen- Investigation performed at the satory mechanisms of the adjacent shoulder muscles. Department of Orthopaedic Surgery, Division of Sports and » Several treatment options are available, depending on the extent and Shoulder Surgery, University of type of , including neurolysis, neurorrhaphy, nerve-grafting, and Colorado, Aurora, Colorado, and nerve transfer. This article highlights the etiology, diagnostic pathways, University of Colorado School of and treatment of both traumatic and iatrogenic axillary nerve injuries. Medicine, Aurora, Colorado

eripheral nerve injuries about trauma, with or without associated sub- the shoulder are a cause of pain luxation of the humeral head, resulting in and dysfunction and have a compression, traction, or contusion of the variety of etiologies and pre- nerve along the deep surface of the deltoid sentations.P Among these, axillary nerve muscle. Such mechanisms of injury fre- injury is one of the most common1,2, quently have been reported in association representing .50% of all infraclavicular with motor-vehicle accidents and contact injuries in a recent study sports (e.g., skiing, football, and rugby)8,9. of 101 patients3. Axillary can Additionally, atraumatic and chronic forms occur in cases of trauma, with 1 study of injury may occur secondary to repetitive demonstrating a rate of 16% (38 of 240) microtrauma (e.g., in overhead throwing among patients with anterior shoulder athletes such as baseball pitchers), brachial dislocation4. It is also an increasingly neuritis, quadrilateral space syndrome, well-known and devastating iatrogenic blunt trauma, and neural entrapment complication of shoulder surgery, with the secondary to space-occupying lesions7. diagnosis being frequently delayed or A delay in diagnosis is concerning as missed5,6. A delay in diagnosis may be clinical outcome is strongly dependent on attributable to absent or delayed symp- the time from the injury to treatment7, with tomatology due to compensation by the a worse prognosis for injuries that remain muscles of the or due to an undiagnosed for more than 6 to 12 occult presentation in the setting of severe months7,8. Therefore, it is critical to rec- associated injuries, such as proximal hu- ognize the clinical settings that demand a meral fracture or shoulder dislocation7. high index of suspicion for axillary nerve Axillary nerve injury also may occur injury and to understand corresponding during other forms of glenohumeral evidence-based treatment options. To this

COPYRIGHT © 2017 BY THE Disclosure: The authors indicated that no external funding was received for any aspect of this work. JOURNAL OF BONE AND JOINT The Disclosure of Potential Conflicts of Interest forms are provided with the online version SURGERY, INCORPORATED of the article (http://links.lww.com/JBJSREV/A219).

JBJS REVIEWS 2017;5(7):e1 · http://dx.doi.org/10.2106/JBJS.RVW.16.00061 1 | Axillary Nerve Palsy and Deltoid Muscle Atony

end, we present an updated review of the neck of the , approximately 4 to discontinuity: , axonotme- anatomy, pathophysiology, diagnosis, 7 cm inferior to the anterolateral corner sis, and neurotmesis. Neurapraxia is the treatment, and prevention of axillary of the acromion, and terminates in the mildest of the 3 categories and typically nerve injury and dysfunction. anterior portion of the deltoid12,13, is caused by excessive compression or supplying collateral sensory and motor traction of the nerve. It is characterized Anatomy branches to the anterior and lateral by conduction abnormality in the ab- The axillary nerve, also known as the segments of this muscle (Fig. 2). The sence of structural deformity; that is, circumflex nerve, is a mixed motor and posterior branch provides motor inner- there is no axonal loss or interruption of sensory nerve that originates from the vation to the posterior portion of the the , , or endo- ventral rami of the fifth and sixth cervical deltoid muscle and neurium. Axillary nerve injury caused nerve roots5. Most commonly, the axil- and provides sensory cutaneous by glenohumeral dislocation or blunt lary nerve arises from fibers of the pos- branches to the skin overlying the pos- trauma is commonly neurapraxic in na- terior cord of the posterior division of terior portion of the deltoid muscle be- ture18. These injuries carry an excellent the brachial plexus10; however, variants fore terminating as the superior lateral prognosis, with complete resolution of have been reported in as many as 20% brachial cutaneous nerve14. During ar- symptoms typically occurring within of patients, in whom the nerve arises throscopic surgery, Yoo et al.15 found days to weeks without surgical inter- from the posterior division of the upper that the axillary nerve typically lies at vention. In contrast, is trunk11. The axillary nerve travels or near the most inferior position of the characterized by an injury to the epi- obliquely along the anterior surface of glenoid (6 o’clock position), approxi- neurium and perineurium. Unlike the and posterior mately 10 to 25 mm from the inferior neurapraxia, axonotmesis involves to the before diving infe- glenoid rim, and is farther away from damage to the and the riorly into the quadrilateral space the operative field when the arm is in sheath but spares Schwann cells involved alongside the posterior humeral cir- abduction and neutral rotation. in initiating the process of Wallerian cumflex artery, in close proximity to degeneration. Although operative treat- the inferomedial capsule (Fig. 1)5,12. Pathophysiology of Nerve Injury ment is usually not required, axonot- The quadrilateral space is bound The severity of peripheral nerve injuries metic injuries may take weeks to months by the long head of the muscle is graded primarily on the basis of the to heal as governed by the rate of medially, the humeral shaft laterally, the amount of axonal discontinuity ob- (maximum rate, teres major and latissimus dorsi muscles served. The 2 most commonly refer- ;1 mm per day), and nerve recovery inferiorly, and the subscapularis muscle enced systems that are used to describe may be incomplete. Neurotmesis com- anteriorly. After passing through the nerve injury are the Seddon classifica- prises the most severe form of injury, quadrilateral space, the nerve travels tion system16 and the Sunderland representing a complete transection of around the posterolateral aspect of the classification system17 (Table I). First all 3 neural layers. Neurotmesis typically humeral neck, where it divides into an- described in 1943, the Seddon classifi- requires surgical nerve-grafting for terior and posterior branches. The an- cation system involves 3 categories that the restoration of nerve functionality terior branch courses around the surgical correspond to the degree of axonal (as described in later sections).

Fig. 1 Posterior-view photograph of a cadaveric right shoulder, demonstrating the quad- rilateral space. The quadrilateral space is bounded by the long head of the triceps muscle medially, the humeral shaft later- ally, the teres major and latissimus dorsi muscles inferiorly, and the subscapularis muscle anteriorly. The axillary nerve travels through this space and around the posterolateral part of the humeral neck, where it divides into anterior and poste- rior branches.

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Fig. 2 Photograph of a cadaveric right humerus with the deltoid muscle belly reflected, revealing the axillary nerve as it branches to the deltoid muscle.

Unfortunately, iatrogenic axillary nerve Clinical Examination the distal two-thirds of the deltoid injuries often involve axonotmesis or Evaluation begins with a thorough muscle, can reveal sensory changes that neurotmesis18. history. A recent history of blunt trauma are suggestive of axillary nerve damage. or shoulder dislocation makes an axillary Despite its utility, this sensory testing Patient Evaluation neurapraxia more likely, whereas does not reliably exclude mixed brachial The diagnosis of axillary nerve injury can penetrating trauma or recent surgery plexus injuries that may be associated be challenging as a result of asymptom- may point toward laceration of the with axillary nerve injury. Because of atic or subclinical presentation. While nerve. It is important to note that a the incompleteness of sensory testing, a complete and thorough physical patient age of .50 years and a lack of a thorough distal strength examination examination should detect the identifying concentric glenohumeral reduction is paramount as brachial plexus injuries patterns of nerve injury, deltoid dysfunc- for .12 hours are known risk factors for may prolong or limit the resolution of tion initially may be masked in young axillary nerve injury following shoulder symptoms, require intensive physio- patients with excellent compensatory dislocation5,18. , or require additional or separate mechanisms or those with difficulty A focused but comprehensive surgical interventions2,19. complying with the examination11.In- physical examination of the shoulder While the testing of deltoid juries resulting in incomplete should be performed bilaterally. Fol- muscle strength can be used to deter- may not be obvious when only the ante- lowing inspection and palpation of the mine axillary nerve function, patients rior or posterior portion of the deltoid shoulder, sensory examination of the who have had a recent operation or muscle is affected. Additionally, in some terminal branch of the axillary nerve traumatic episode may have difficulty cases, the patient may retain nearly full (the superior lateral brachial cutaneous performing such testing, which may abduction of the shoulder secondary nerve), which supplies sensory innerva- present a challenge when pain pre- to supraspinatus compensation. tion to the lateral aspect of the arm near vents a comprehensive physical

TABLE I Seddon and Sunderland Classification Systems for Peripheral Nerve Injuries16,17

Seddon Sunderland Injury Type Neurological Deficits

Neurapraxia I Intrafascicular with conduction Neuritis, paresthesias block, possible segmental demyelination Axonotmesis II Severed axon, intact Paresthesia, episodic dysesthesias III Severed axon, disruption of endoneurium Paresthesia, dysesthesia IV Disruption of endoneurium and Hypoesthesia, dysesthesia, neuroma perineurium Neurotmesis V Complete nerve discontinuity Anesthesia, intractable pain, neuroma VI Combination of above Mixed presentation

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examination. Special physical exami- and asking the patient to abduct the However, slight inferior displacement, nation techniques have been described shoulder. If the patient is unable to fully or pseudosubluxation, of the humeral to aid in the identification of isolated abduct the shoulder in this position, head may be evident, indicating deltoid deltoid muscle dysfunction. The the examiner assists with abduction and muscle dysfunction. Advanced cervical swallow-tail test (Fig. 3) is performed asks the patient to maintain this posi- spine imaging may assist in ruling out by having the patient bend forward at tion. Any abduction lag indicates a a more proximal lesion23,24. Advanced the waist and maximally extend the positive test. The internal rotation of imaging studies, including computed shoulders, first with elbows extended the shoulder in this maneuver displaces tomography (CT) and magnetic reso- and then with elbows flexed. A dif- the supraspinatus tendon insertion nance imaging (MRI), also can be per- ference in shoulder extension between anteriorly, decreasing its ability to aid formed, depending on the mechanism the normal and affected sides of .20° in shoulder abduction and increasing and clinical suspicion of the underlying indicates a positive test20. The deltoid the sensitivity of the examination. injury. As in other regions of the body, extension lag test involves the exam- Further clinical examination fol- MRI typically is superior for the evalu- iner maximally extending the shoulder lowing the identification of axillary ation of soft-tissue lesions such as nerve and elbows of the patient and then nerve injury often allows for determi- injuries. MRI scans traditionally have asking the patient to hold that posi- nation of the location of the lesion as been useful when space-occupying le- tion. A lag in shoulder extension on it relates to the quadrilateral space. If sions or fibrotic are compressing the affected side as compared with the axillary lesion spares the posterior the nerve; however, recent advances in the contralateral side is considered portion of the deltoid and teres minor MRI have allowed for detailed evalua- a positive test21. muscles, the lesion is distal to the tion of nerve injuries resulting from both The abduction in internal rotation quadrilateral space8. traumatic and surgical causes. Magnetic test22 (Fig. 4) is our preferred method for resonance neurography also has been evaluating deltoid muscle function as it Imaging and Other Testing proposed as a method for visualizing has been shown to be superior to both Standard shoulder radiographs should the axillary nerve. the deltoid muscle extension lag test and be made for patients with suspected When clinical presentation and/or swallow-tail test21. It is performed by deltoid muscle atony. Conventional ra- imaging studies are concerning for an ax- placing the patient’s shoulder in full diographs often will be normal outside illary nerve injury, electromyography and internal rotation with the elbow flexed the setting of dislocation or fracture. nerve conduction studies (EMG/NCS)

Fig. 3 Photographs illustrating the swallow-tail test. In a normal test (Fig. 3-A), both shoulders are fully extended to the same level. However, in an abnormal test (Fig. 3-B), the posterior fibers of the deltoid muscle fail to fire, thus limiting full extension of the affected shoulder.

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Fig. 4 Figs. 4-A and 4-B Photographs illustrating the abduction in internal rotation test. Fig. 4-A The patient is instructed to abduct and internally rotate the shoulder actively with both elbows flexed. Fig. 4-B If any discrepancies are noted, the examiner repeats the maneuver (passively) and the patient is instructed to maintain the position. If the patient is not able to do so, the test is positive. can be used to confirm the diagnosis. association with acute shoulder disloca- exiting the quadrilateral space are com- One to 4 weeks typically are required tions, complete spontaneous recovery pressed by surgical adhesions, glenoid for changes to manifest on EMG/NCS usually occurs, with reported rates in the paralabral cysts, ganglion cysts, muscle following an axial nerve injury24. literature ranging from 87.5% to 100% hypertrophy, or displaced scapular Therefore, delaying EMG/NCS until of cases3,24. In the study by Visser fractures14,27. Quadrilateral space syn- approximately 4 weeks can be helpful et al.24, 4 of 32 patients in whom a severe drome also can occur after prolonged for establishing a post-injury baseline axillary nerve injury was confirmed on lying in the lateral decubitus position28. for the patient and can help to better the basis of both clinical examination Patients who have sustained blunt delineate the full extent of the injury. and EMG findings failed to recover full trauma to the axillary nerve distal to the function. However, only minor residual quadrilateral space often present with Etiologies symptomatology remained. Interest- soft-tissue swelling throughout the an- Non-Surgical Injuries ingly, those authors did not find an in- terolateral aspect of the shoulder associ- Understanding the etiology or mecha- creasing severity of nerve injury, butthey ated with full or partial deltoid muscle nism of injury is of paramount impor- did find that the risk of nerve injury in paralysis and variable sensory loss. In tance as the treatment of an axillary association with dislocation increased some cases, sensation may be normal nerve injury is based on the severity and with age (p , 0.007). Results have been in the presence of complete deltoid type of injury that has been sustained. A similarly favorable in patients with low- muscle paralysis. detailed clinical history is vital for treat- energy torsional and compression-type In cases of blunt trauma, outcomes ment decision-making as each mecha- injuries. Guerra and Schroeder26 have been less favorable. Perlmutter nism has a characteristic injury pattern. reported on 5 patients with torsional et al.29 reported on 11 athletes who Operative treatment typically is not in- nerve injury, all of whom had good or sustained axillary nerve injury as a result dicated for low-energy, non-penetrating excellent restoration of motor function of direct blunt trauma. At the time of the traumatic injuries. Such injuries are after a mean duration of follow-up latest follow-up (mean, 73.8 months) all usually traction, torsion, or compression of 33 months. patients were still experiencing clinically neurapraxias in which the axon is not Compression of the axillary nerve apparent motor and sensory deficits of disrupted. Rather, neurological symp- can occur in association with blunt, non- the axillary nerve. However, 10 of the 11 toms occur following trauma as a result penetrating trauma in the absence of patients returned to the preinjury level of a conduction block due to transient fracture or dislocation11. These mecha- of athletics. Similarly, Berry and Bril30 demyelination or intrafascicular edema nisms typically involve a direct blow to reported on 13 patients who experi- in the nerve. the anterolateral aspect of the deltoid enced axillary nerve injury as a result of Shoulder dislocation is one of the muscle. If compression occurs at the site blunt trauma without fracture or dislo- leading causes of traction injury of the where the nerve exits the quadrilateral cation. Only 6 patients had complete axillary nerve, with the reported rates of space, isolated posterior deltoid muscle or nearly complete resolution of neuro- nerve injury following dislocation rang- paralysis and sensory loss along the su- logical symptoms. Certainly, more ing between 5% and 54%5,23. Injuries perior lateral brachial cutaneous distri- studies are needed to determine the to the nerve occur in association with bution are observed. This presentation natural history of, and best treatment anteroinferior shoulder subluxation, also can occur in cases of quadrilateral for, these types of injuries. frank dislocation, and Bankart lesions25. space syndrome, in which the axillary Torsional peripheral nerve injuries When nerve damage occurs in nerve and circumflex humeral artery are exceedingly rare and involve rotation

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or twisting of the axillary nerve on itself, paid to factors that increase the predis- trapezius tendon transfer to restore resulting in a so-called hourglass-like position to iatrogenic injury, including deltoid functionality. Nagda et al.38 deformity. While the underlying etiol- current or previous use of methotrexate, found that 57% of 30 patients dem- ogy of these injuries remains unclear, it is a history of shoulder surgery, a history onstrated EMG findings consistent generally accepted that posttraumatic of radiation treatment, a preoperative with impending intraoperative com- cases of axillary nerve injury occur sec- passive external rotation range of motion promise of nerve function during ondary to and fibrosis of ,10°, and decreased operative positioning of the involved extremity at of epineurial and perineurial tissue while time38,39. the time of total shoulder arthroplasty. spontaneous cases of nerve injury occur Several surgical procedures have Fifty percent of the nerve events oc- secondary to forceful movements that been implicated in axillary nerve injury curred while the extremity was placed cause stretching of the axillary nerve over as well. Among these, the Latarjet pro- in abduction, external rotation, and the scapulohumeral joint of the medial cedure, which is a means of glenohu- extension, and the other 50% occurred aspect of the shoulder. A clinical hall- meral joint stabilization that includes during preparation of the glenoid. mark of axillary nerve torsion injury is transfer of the coracoid process to the While these changes may have been the abrupt onset of pain, often associated anterior aspect of the glenoid, has be- related to retractor tension on the with pronounced motor deficits. Clini- come increasingly popular34. While the nerve, repositioning of the arm into a cal and electrophysiological recovery Latarjet procedure is effective, a recent more neutral position, rather than re- often do not occur even months after the systematic review of 1,904 such proce- tractor removal alone, was more likely initial injury. Ultimately, persistent is- dures demonstrated a relatively high to return EMG readings to baseline. chemia of the axillary nerve may result rate of neurovascular injury (1.8%), Limb lengthening associated with in exudation of proteins into the epi- including 6 axillary nerve injuries40. reverse total shoulder arthroplasty neurium and subsequent fibrosis that The cadaveric study by Freehill et al. increases the native tension across the may be detectable on MRI scans23. demonstrated consistent postoperative entire brachial plexus, placing these Other comorbidities or medical overlap between the musculocutaneous structures at risk of peripheral nerve conditions also can confound the diag- and axillary as well as medial palsies and other neurological compli- nosis of axillary nerve injury. Diabetes displacement of both nerves relative to cations48. A recent cadaveric study mellitus, thyroid disease, renal disease, their preoperative positions during the quantified the proximity of the axillary autoimmune disorders, or chronic liver Latarjet procedure41. Delaney et al. used nerve to the implant after reverse disease may lead to peripheral neuropa- intraoperative neuromonitoring during shoulder arthroplasty49. The principal thies that can symptomatically mimic the procedure and found the nerve to finding of that study was that the main isolated injury to the axillary nerve31,32. be most at risk during glenoid exposure anterior branch of the axillary nerve was Furthermore, cervical compression of and graft insertion42. Additionally, approximately 5 mm away from the either the C5 or C6 nerve roots may 79.4% of the nerve alerts occurred when humeral prosthetic implant. Addition- cause isolated axillary symptomatology the arm was in external rotation, indi- ally, the nerve was never closer than or may contribute to a so-called double- cating that while the axillary nerve is 15 mm to the glenosphere, which crush phenomenon in cases of both under the least amount of tension in constituted a safer implant with respect cervical compression and distal axillary external rotation, that position also to the nerve. nerve injury30. A thorough history and may bring the axillary nerve closest to the The open inferior capsular shift, physical examination are required to surgical field42. In order to avoid injury, which reduces capsular redundancy and appreciate these comorbidities and to those authors advised against excessive restores anterior, inferior, and posterior avoid misdiagnosis. retraction and a more superior place- stability, is another procedure in which ment of the coracoid graft. damage to the axillary nerve can occur50. Surgical Injuries Axillary nerve injury is also a well- During the procedure, excessive inferior Iatrogenic injury is a frequent and pre- documented complication of total dissection or thermal injury resulting ventable cause of axillary nerve palsy. shoulder arthroplasty. Neurological from electrocauterization can cause Open injuries are more likely to result injuries occur in association with about damage to the axillary nerve as it courses in axonotmesis or neurotmesis of the 1% of total shoulder arthroplasty pro- across the operative field beneath the nerve, which require operative repair. cedures, with the axillary nerve being glenohumeral ligament. This type of Mechanisms of intraoperative nerve most commonly affected43-47.Ina injury also can occur in association with injury include limb malpositioning, systematic review, Bohsali et al.43 arthroscopic or open Bankart lesion inadvertent suturing, heat penetration, found that 10 (77%) of 13 axillary repair51. Neer and Foster reported aggressive retractor placement, and ex- nerve injuries resolved spontaneously postoperative axillary neurapraxia in 3 cessive inferior dissection of the shoulder without surgery while 1 patient with (8%) of 40 patients undergoing open capsule15,33-37. Attention also should be a transected axillary nerve required inferior capsular shift procedures52.

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A limited body of literature has and surgical precision in order to avoid Natural History described cases of axillary nerve com- possible iatrogenic injury. The vast majority of axillary nerve in- promise after proximal humeral fixa- Reverse shoulder arthroplasty is juries are temporary neurapraxias, which tion. One cadaveric study showed that becoming more common, and limb typically resolve within 6 to 12 months the axillary nerve could be elevated lengthening associated with this proce- after the index injury. Nevertheless, almost 14 mm from the bone without dure may increase the native tension permanent axillary nerve deficit also becoming taut53.Nonetheless,the across the entire brachial plexus and the has been reported30,60. Regardless of the nerve could be exposed to greater axillary nerve, thus posing a risk of pe- fact that nerve damage can be devastat- tension forces during manipulation ripheral nerve palsies and other neuro- ing for the patient, previous reports of the fracture fragments, fibrosis, or logical complications48. A recent have described nearly normal shoulder osteosynthesis materials. Park and cadaveric study also quantified the lo- function after closed axillary nerve Jeong, in a consecutive series of 21 cation of the axillary nerve in relation to injury (although none of those patients with proximal humeral frac- the implant following reverse shoulder reports documented permanent nerve tures that were treated with minimally arthroplasty and suggested that nerve damage)29,61-64. It also has been estab- invasive percutaneous plating, damage can occur secondary to the lished that a delay in diagnosis is strongly reported 1 case of axillary nerve pare- proximity of the axillary nerve during correlated with the final outcome and sis54. Additionally, humeral nail the placement of a reverse prosthesis. that a less-than-optimal prognosis can fixation is not without risks. A ca- The principal finding of that study was be expected if the diagnosis is made .6 daveric study demonstrated that the that the main anterior branch of the months after the index injury. axillary nerve can be damaged during axillary nerve was approximately 5 mm the insertion of the locking screws away from the humeral prosthetic im- Nonoperative Treatment despite the use of protection sleeves plant, placing it at risk for irritation, With the exception of certain cases of and trocars55. abutment, or injury. However, the nerve quadrilateral space syndrome, neu- Given our understanding of the was never closer than 15 mm to the rapraxic injuries usually are treated complications related to open surgical convex hemispherical glenoid prosthesis nonoperatively. Several case series in- procedures about the shoulder, the ma- (glenosphere)49. volving patients who have had compli- jority of primary stabilization proce- Injury involving the axillary nerve cations after shoulder surgery have dures are currently being performed also may occur in association with shown high rates of spontaneous arthroscopically. As a result, it is im- proximal humeral fractures or during recovery following axillary nerve portant for surgeons to consider the the reduction and fixation of such frac- neurapraxia18,39,43; however, compara- close proximity of the axillary nerve even tures. A limited body of literature, tive studies with operative treatment are during arthroscopic procedures. Several however, has described cases of axillary lacking. Nonoperative treatment should reports have described the close prox- nerve compromise following proximal include a rehabilitation program em- imity of the axillary nerve to the inferior humeral fixation. As noted above, ca- phasizing passive and active range of axillary pouch during the placement of daveric laboratory dissection has dem- motion as well as strengthening of the arthroscopic capsular plication sutures onstrated that the axillary nerve can be rotator cuff, deltoid muscle, and peri- for the treatment of multidirectional elevated nearly 14 mm from the bone scapular musculature7,65. Shoulder instability, for anteroinferior capsulola- without being placed under tension53. contracture typically is not associated bral repair, or for complex arthroscopic Tension may, however, be placed on the with axillary nerve injury unless an ex- reconstruction15,33-37. However, recent nerve during reduction or manipulation tensive ligamentous or osseous injury reports also have shown that the nerve of fracture fragments if the nerve is is present30. If no apparent clinical im- may be as close as 7 mm during bicortical tethered by fibrosis or if the nerve is provement is evident at 3 months fol- drilling at the time of biceps tenodesis abutting fixation implants. Park and lowing the initial insult, repeat EMG/ procedures or during the placement of Jeong, in a consecutive series of 21 pa- NCS should be performed, and serial standard or accessory anterior or poste- tients with proximal humeral fractures EMG studies may be performed to rior portals or posteroinferior (7 o’clock) that were treated with minimally inva- monitor the progression of recovery39.If arthroscopic portals56-59. While axillary sive percutaneous plating, reported there is no improvement in terms of the nerve injuries resulting from arthro- 1 case of axillary nerve paresis54. In ad- clinical and/or electrophysiological re- scopic procedures remain rare, the dition, humeral nail fixation is not covery status within 3 to 4 months after reporting on such complications is lim- without risks. A cadaveric study dem- the injury, operative treatment should ited and therefore these injuries may be onstrated that the axillary nerve can be be considered18. Operative treatment more frequent than presently recog- damaged during the insertion of the typically is recommended between 3 nized. Surgeons must maintain a high locking screws despite the use of pro- and 6 months after the injury for level of attention to anatomic landmarks tection sleeves and trocars55. patients lacking evidence of clinical or

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electrophysiological improvement11,18. posterior approach between the long of direct repair. Kline and Kim reported We support surgical exploration of the head of the triceps and teres major on 3 patients who underwent direct end- axillary nerve within 3 to 4 months after muscles. However, both anterior and to-end suture repair of the axillary nerve the injury if testing shows a lack of posterior approaches may be required to that resulted in clinical recovery of del- electrophysiological recovery; these achieve adequate debridement or toid muscle strength71. Terzis and specific interventions will be discussed decompression69,71,72. For this reason, Barmpitsioti also performed direct re- in later sections. The strength of this preoperative MRI is extremely helpful pair of the axillary nerve in a larger study recommendation is graded as weak on for determining the etiology and loca- but did not report on outcomes specific the basis of the limited available litera- tion of neurological symptoms. to those patients74. ture, and comparative studies between Outcomes following neurolysis for expectant management and operative the treatment of stretch or contusion Nerve-Grafting and Neurotization repair are needed. injuries have been favorable. Kline and In some cases of axillary nerve injury or Kim found that, even in patients with transection, scarring and retraction have Operative Treatment complete clinical nerve loss, axillary occurred, making repair or other less- The results of operative treatment of nerve recovery was possible with isolated invasive procedures difficult. In such axillary nerve injuries are optimal when neurolysis as long as intraoperative nerve cases, nerve reconstruction by nerve- surgery is performed within 3 to 6 action potentials were observed71. grafting or nerve transfer, known as months after the injury7. Outcomes of However, clinical and patient-reported neurotization, is recommended. Al- surgical treatment for axillary nerve in- outcomes are poorer when concomitant though typically recommended in jury are worse beyond this time frame, distal peripheral nerve injury in the arm chronic settings, neurotization also may with only marginal benefits seen when or hand, or associated mixed brachial be recommended in cases of severe or surgery is performed $12 months after plexus injuries, are present73. segmental traumatic axillary injuries, the injury66-68.These recommendations especially those associated with a root or are based on case series, and further Neurorrhaphy cord avulsion, because of the need for comparative studies are needed to opti- Primary repair of the axillary nerve with rapid regeneration of nerve fibers75-77. mize the timing of surgery. Four stan- suture, also known as neurorrhaphy, is Neurotization involves the transfer dard modalities of operative treatment indicated for the treatment of acute of autologous nerves from redundant or are generally utilized: neurolysis, neu- transections or lacerations of the nerve less-used areas of the body. Common rorrhaphy, nerve-grafting, and neuroti- and in cases in which the nerve is found harvest sites include the thoracodorsal, zation8. The choice between treatment to be cleanly bisected with minimal phrenic, spinal accessory, and intercostal modalities is contingent on the findings scarring. Primary repair is particularly nerves, with promising results for the observed during operative exploration. advantageous for the treatment of the correction of axillary nerve palsy75,76. axillary nerve (as compared with other Reports of transferring the medial tri- Neurolysis peripheral nerves) because of its simple ceps branch of the to the Neurolysis is a procedure that involves fascicular structure and close proximity axillary nerve (triceps-to-axillary trans- excision and debridement of tissue to effector muscles73. For this reason, fer) have demonstrated reasonable around the nerve (external neurolysis) primary repair is preferred to nerve- outcomes77,78. Triceps-to-axillary or removal of scarred or fibrosed nerve grafting or neurotization. In patients transfers have been particularly success- tissue within the perineurium (internal with acute injuries, it is important to ful for the treatment of acute axillary neurolysis). In cases of axillary nerve perform the repair as soon as possible nerve palsy77,78. However, other studies palsy, external neurolysis is indicated as fibrosis will lead to increased dissec- have shown that outcomes following the if the nerve is found to be intact but tion and blunted or distorted repair transfer of the medial triceps branch entrapped69,70. This type of entrapment ends, which may negatively impact of the radial nerve are less predictable, is seen in patients with a history of outcomes71,73. If the nerve cannot and negative prognostic factors include shoulder surgery as well as overhead be mobilized intraoperatively, or if delayed time to surgery, increased age, athletes in whom fibrosis develops as a tension-free anastomosis cannot be and increased body mass index (BMI)72. a result of repetitive microtrauma69. achieved, nerve-grafting may be Nerve-grafting also is an option for An anterior approach with the pa- necessary. the treatment of large, traumatic nerve tient in a modified beach-chair position Focal, isolated transection lesions lesions or in cases in which considerable or the lateral decubitus position can of the axillary nerve are rare, and neuroma resection is required. Short be used to achieve direct access to the mobilization is often difficult because nerve grafts have been associated with nerve71. If the area of fibrosis is sus- of retraction of the nerve ends or sur- better outcomes than long grafts23, pected to be in the quadrilateral space, rounding musculature. As a result, there which initially showed disappointing visualization can be attained through a is a scarcity of literature on the outcomes results79. However, a recent study by

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Wolfe et al. showed no difference be- procedure. However, this tactile ma- dysfunction, motor weakness, or a tween long nerve grafts and triceps-to- neuver does not provide direct infor- combination of these symptoms. An axillary nerve transfers in adult patients mation regarding compressive or understanding of the pathophysiology with axillary nerve palsy80. conductive injuries to a nerve in conti- of nerve injury aids in clinical decision- nuity. Alternatively, deltoid muscle at- making, which may result in early Prevention rophy can be minimized by using an operative intervention before irreversi- Several measures can be routinely fol- extended deltopectoral approach, which ble nerve damage occurs. In addition, lowed to prevent iatrogenic axillary preserves both the origin and the inser- an understanding of axillary nerve nerve injury. Proper understanding of tion of the deltoid muscle. anatomy is important for diagnosis and local anatomy is crucial for the avoid- Several studies have demon- treatment as well as for reducing the risk ance of injury to the axillary nerve, strated that the position of the axil- of intraoperative iatrogenic injury. particularly when planning surgical in- lary nerve varies as a function of Additional studies are needed to provide cisions over the lateral portion of the abduction, extension, and rotation of both guidelines for treatment and future deltoid muscle, placing arthroscopic the humerus12,82. Adduction of the directions as the indications and types portals, or performing capsular plica- humerus moves the axillary nerve closer of shoulder procedures continue tions or releases, as previously discussed. to the operative field and glenohumeral to expand. In addition, arm positioning during the joint, whereas external rotation at 45° of operation is vital. A cephalad-directed horizontal glenohumeral flexion moves NOTE: force on the flexed elbow helps to the axillary nerve away from the field. The authors thank Vivek eliminate inferior translation of the The arm should be in the latter position Chadayammuri, BS, for his critical humerus and decreases the risk of during deep dissection and retractor review of the manuscript. compression or traction injury of the placement near the insertion of inferior 1 axillary nerve81,82.Werecommenda capsule10. During arthroscopic surgery, Justin J. Mitchell, MD , Christopher Chen, MD2, mobile arm positioner with the patient the axillary nerve is farther away from the Daniel J. Liechti, MD3, in the beach-chair position. The use field with the arm in abduction and Austin Heare, MD2, of shoulder-specific operating tables neutral rotation15. Additional studies Jorge Chahla, MD3, should be considered in order to im- are required to determine how the po- Jonathan T. Bravman, MD2,4 prove patient comfort, body alignment, sition of the axillary nerve varies 1Division of Orthopaedic Sports and safety. according to surgical approach, type Medicine, Gundersen Health System, In order to preserve the function of procedure, and stage of procedure. La Crosse, Wisconsin of the deltoid muscle, the location and Extreme ranges of arm positioning, course of the axillary nerve should be particularly external rotation, should 2Department of Orthopaedic Surgery, carefully identified, particularly during not be maintained for extended periods Division of and Shoulder 42 Surgery, University of Colorado, open capsular releases, arthroplasty, or of time . Aurora, Colorado arthroscopic procedures near the infe- Because the optimal balance be- rior capsule. In procedures involving tween visualization and safety of the 3Steadman Philippon Research Institute, open anterior approaches to the shoul- axillary nerve is difficult to assess, intra- Vail, Colorado der, the axillary nerve courses across the operative neuromonitoring may be 4University of Colorado School of operative field, and the course of the helpful for identifying impending or Medicine, Aurora, Colorado nerve can be delineated with use of the subclinical nerve damage secondary to “tug” test81. This test is performed by retractor placement or limb malposi- E-mail address for J.T. Bravman: simultaneously palpating the axillary tioning. While multiple studies have [email protected] nerve both medial and lateral to the found that this technique may prevent humeral shaft with both index fingers. iatrogenic nerve damage, cost-benefit References Once the surgeon has located the nerve analyses are needed to assess the effec- 1. Apaydin N, Uz A, Bozkurt M, Elhan A. The 33,83 anatomic relationships of the axillary nerve and medially as it courses inferiorly on the tiveness of this practice . Currently, surgical landmarks for its localization from the subscapularis and laterally on the un- intraoperative neuromonitoring is best anterior aspect of the shoulder. Clin Anat. 2007 Apr;20(3):273-7. dersurface of the deltoid muscle, a gentle considered for patients with anticipated 2. Friedman AH, Nunley JA 2nd, Urbaniak JR, “tug” is applied by either finger and can risk factors for nerve injury, as previously Goldner RD. Repair of isolated axillary nerve be felt by the contralateral index finger. discussed. lesions after infraclavicular brachial plexus injuries: case reports. . 1990 Sep; This maneuver allows for direct palpa- 27(3):403-7. tion of the axillary nerve in order to as- Overview 3. Hems TE, Mahmood F. Injuries of the terminal branches of the infraclavicular brachial plexus: sess its continuity and to identify its Axillary nerve injuries may present patterns of injury, management and outcome. location for protection throughout the as sensory deficits, deltoid muscle J Bone Joint Surg Br. 2012 Jun;94(6):799-804.

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