The posterior branch of the axillary nerve: an anatomic study

Anatomical considerations for nerve transfer in axillary nerve injury

This study investigated the anatomical details of the axillary and radial nerves in 50 upper limbs from 29 adult formalin-embalmed cadavers, and ten fresh upper limbs. The focus was on understanding the course, division, and ramifications of these nerves to improve treatment of shoulder dysfunction caused by axillary nerve damage. The axillary nerve divided anteriorly and posteriorly before passing the quadrangular space in all specimens, with specific distances to the first ramifications. It was found that the deltoid muscle's clavicular and acromial parts were always innervated by the anterior division of the axillary nerve, whereas the spinous part was variably innervated. The longest and thickest branches of the radial nerve to the triceps muscles were identified, with no statistically significant differences in fiber numbers among triceps branches. The study concludes that nerve transfer to the anterior division of the axillary nerve can restore the deltoid muscle in about 86% of shoulders, and the teres minor muscle can be restored by nerve transfer to the posterior division. The medial head branch and long head branch of radial nerve were identified as the best donor options.

Posterior Deltoid Function After Transfer of Branch to the Long Head Triceps Brachii of the Radial Nerve to the Anterior Branch of the Axillary Nerve

PURPOSE

The aim of this study was to evaluate the function of the posterior part of the deltoid after nerve transfer of the long head triceps branch of the radial nerve to the anterior branch of the axillary nerve in patients with an upper brachial plexus injury or isolated axillary nerve injury.

METHODS

We retrospectively reviewed 26 patients diagnosed with an upper brachial plexus injury or isolated axillary nerve injury who underwent nerve transfer of the long head triceps muscle branch of the radial nerve to the anterior branch of the axillary nerve in our institute between 2012 and 2017. Data on age, sex, the mechanism of injury, the pattern of injury, and operative treatment were collected from medical records. Preoperative and postoperative clinical examinations, including motor powers of shoulder abduction and extension according to Medical Research Council grading, were evaluated. At a minimum of 2 years after the operation, we evaluated the recovery of the posterior deltoid function using the swallow-tail test.

RESULTS

Twenty-two patients (84.6%) had recovery of posterior deltoid function confirmed by the swallow-tail test. There were 23 patients (88.5%) who achieved at least Medical Research Council grade 4 of shoulder abduction.

CONCLUSIONS

Nerve transfer from the branch to the long head triceps to the anterior branch of the axillary nerve is an effective technique for restoring deltoid function in an upper brachial plexus injury or isolated axillary nerve injury. This technique can provide shoulder abduction and shoulder extension, which are the functions of the posterior deltoid muscle.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

The surgical anatomy of the axillary approach for nerve transfer procedures targeting the axillary nerve

PURPOSE

The exact relational anatomy for the anterior axillary approach, targeting the axillary nerve for nerve transfers/grafts, has not been fully investigated. Therefore, this study aimed to dissect and document the gross anatomy surrounding this approach, specifically regarding the axillary nerve and its branches.

METHODS

Fifty-one formalin-fixed cadavers (98 axilla) were bilaterally dissected simulating the axillary approach. Measurements were taken to quantify distances between identifiable anatomical landmarks and relevant neurovascular structures encountered during this approach. The musculo-arterial triangle, described by Bertelli et al., to aid in identification on localization of the axillary nerve, was also assessed.

RESULTS

From the origin of the axillary nerve till (1) latissimus dorsi was 62.3 ± 10.7 mm and till (2) its division into anterior and posterior branches was 38.8 ± 9.6 mm. The origin of the teres minor branch along the posterior division of the axillary nerve was recorded as 6.4 ± 2.9 mm in females and 7.4 ± 2.8 mm in males. The musculo-arterial triangle reliably identified the axillary nerve in only 60.2% of the sample.

CONCLUSION

The results clearly demonstrate that the axillary nerve and its divisions can be easily identified with this approach. The proximal axillary nerve, however, was situated deep and therefore challenging to expose. The musculo-arterial triangle was relatively successful in localising the axillary nerve, however, more consistent landmarks such as the latissimus dorsi, subscapularis, and quadrangular space have been suggested. The axillary approach may serve as a reliable and safe method to reach the axillary nerve and its divisions, allowing for adequate exposure when considering a nerve transfer or graft.

Teres Minor Muscle Atrophy: Anatomy, Patterns, and Clinical Manifestations

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Isolated teres minor atrophy has a reported incidence in the literature of 3% to 6.2%.

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There are 2 distinct muscular bundles of the teres minor that have varying degrees of atrophy. Fatty degeneration of the medial-dorsal component exceeds that of the lateral-ventral component in most cases.

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A healthy and intact teres minor muscle is of functional importance in the setting of a complete infraspinatus tear because it becomes the only external rotator of the shoulder joint.

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Clinical and functional outcomes after rotator cuff repair and reverse shoulder arthroplasty for patients with teres minor atrophy in the setting of a rotator cuff tear are still controversial.

The Axillary Nerve Danger Zone in Percutaneous Fixation in the Pediatric Shoulder: The "1-Mountain-3-Valleys" Principle

BACKGROUND

Adult literature cites an axillary nerve danger zone of 5 to 7 cm distal to the acromion tip for open or percutaneous shoulder surgery, but that may not be valid for younger patients. This study sought to quantify the course of the axillary nerve in adolescent patients with reference to easily identifiable intraoperative anatomic and radiographic parameters.

METHODS

A single-institution hospital database was reviewed for shoulder magnetic resonance images (MRIs) in patients 10 to 17 years old. One hundred and one MRIs from patients with a mean age of 15.6 ± 1.2 years (range, 10 to 17 years) were included. Axillary nerve branches were identified in the coronal plane as they passed lateral to the proximal humerus and were measured in relation to identifiable intraoperative surface and radiographic landmarks, including the acromion tip, apex of the humeral head, lateral physis, and central apex of the physis. The physeal apex height (i.e., 1 "mountain") was defined as the vertical distance between the most lateral point of the humeral physis (LPHP) and the central intraosseous apex of the physis.

RESULTS

Axillary nerve branches were found in all specimens, adjacent to the lateral cortex of the proximal humerus. A mean of 3.7 branches (range, 2 to 6) were found. The mean distance from the most proximal branch (BR1) to the most distal branch (BR2) was 11.7 mm. The pediatric danger zone for the axillary nerve branches ranged from 6.6 mm proximal to 33.1 mm distal to the LPHP. The danger zone in relation to percent of physeal apex height included from 62% proximal to 242% distal to the LPHP.

CONCLUSIONS

All branches were found distal to the apex of the physis (1 "mountain" height proximal to the LPHP). Distal to the LPHP, no branches were found beyond a distance of 3 times the physeal apex height (3 "valleys"). In children and adolescents, percutaneous fixation of the proximal humerus should be performed with cortical penetration outside of this range. These parameters serve as readily identifiable intraoperative radiographic landmarks to minimize iatrogenic nerve injury.

CLINICAL RELEVANCE

This study provides valuable landmarks for percutaneous approaches to the proximal humerus. The surgical approach for the placement of percutaneous implants should be adjusted accordingly (i.e., performed at least 1 mountain proximal or 3 valleys distal to the LPHP) in order to prevent iatrogenic injury to the axillary nerve.

Entrapment Neuropathies of the Shoulder

Entrapment neuropathies of the shoulder most commonly involve the suprascapular or axillary nerves, and they primarily affect the younger, athletic patient population. The extremes of shoulder mobility required for competitive overhead athletes, particularly in the position of abduction and external rotation, place this cohort at particular risk. Anatomically, the suprascapular nerve is most prone to entrapment at the level of the suprascapular or spinoglenoid notch; the axillary nerve is most prone to entrapment as it traverses the confines of the quadrilateral space.Radiographs should be ordered as a primary imaging study to evaluate for obvious pathology occurring along the course of the nerves or for pathology predisposing the patient to nerve injury. Magnetic resonance imaging plays a role in not only identifying any mass-compressing lesion along the course of the nerve, but also in identifying muscle signal changes typical for denervation and/or fatty atrophy in the distribution of the involved nerve.

Incidence, Risk Factors, Prevention, and Management of Peripheral Nerve Injuries Following Shoulder Arthroplasty

In this article, the authors review the incidence and causes of iatrogenic peripheral nerve injuries following shoulder arthroplasty and provide preventative measures to decrease nerve injury rate and management options. They describe common direct and indirect causes of injury such as laceration and retractor use versus arm positioning and lengthening, respectively. Preventative measures include an understanding of anatomy and high-risk locations in the shoulder, minimizing extreme ranges of arm motion and utilization of intraoperative nerve monitoring. Lastly, the authors review diagnosis and management of neurologic symptoms including how and when to use electrodiagnostic studies, nerve grafts, transfers, or muscle/tendon transfers.

Permeable spaces between glenohumeral ligaments as potential gateways for rapid regional anesthesia of the shoulder

Shoulder pain is a highly prevalent condition, often resulting in major life limitations, and requiring effective treatments. In this work, we explore the anatomical basis of a proposed approach to the regional anesthesia of the shoulder through a single injection under the subscapularis muscle. Bilateral experimental injections in shoulders from body donors (Radiolar ® and Methylene-Blue) under the subscapular muscle (n = 11) and cadaveric systematic dissections of other 35 shoulders from body donors were performed. Injectate spread was then qualitatively assessed. Long axis of permeable foramina in the anterior aspect of the shoulder joint capsule was measured in centimeters using a digital caliper. More than 40% of specimens had at least one permeable space (Weitbrech and/or Rouvière foramina) communicating the subscapular bursa and the articular space. We further demonstrate that an ultrasonography-guided injection under the subscapularis muscle allows the spread of the injectate through the anterior, inferior and posterodorsal walls of the articular capsule, the subacromial bursa, and the bicipital groove, as well as into the articular space for some injections. The odds of accidental intraarticular injection decrease when injecting with low volumes. This anatomical study provides a detailed description of foramina between glenohumeral ligaments. Furthermore, the data shown in this work supports, as a proof of concept, a safe alternative for rapid and specific blockade of terminal sensory branches innervating the shoulder joint capsule.

Definition of a Risk Zone for the Axillary Nerve Based on Superficial Landmarks

BACKGROUND

The aim of this study was to investigate the axillary nerve's location along superficial anatomical landmarks, and to define a convenient risk zone.

METHODS

A total of 123 upper extremities were evaluated. After dissection of the axillary nerve, the vertical distance between the upper border of the anterolateral edge of the acromion and the proximal border of the nerve was measured. Furthermore, the interval between the proximal border and the distal border of the axillary nerve's branches was evaluated. The interval between the distal border of the branches and the most distal part of the lateral humeral epicondyle was measured. The distance between the anterolateral edge of the acromion and the lateral humeral epicondyle was evaluated. Measurements were expressed as proportions with respect to the distance between the acromion and the lateral humeral epicondyle.

RESULTS

The distance between the acromion and the proximal border of the axillary nerve's branches was at a height of 10 percent of the distance between the acromion and the lateral humeral epicondyle, starting from the acromion (90 percent when starting from the lateral humeral epicondyle). The interval between the proximal and distal margins of the axillary nerve's branches was between 10 percent and 30 to 35 percent of this interval, starting from the acromion (65 to 70 percent when starting from the lateral humeral epicondyle).

CONCLUSIONS

The authors were able to locate the branches of the axillary nerve at an interval between 10 and 35 percent of the distance between the acromion and the lateral humeral epicondyle, starting from the acromion. This makes the proximal third of this distance an easily applicable risk zone during shoulder surgery.

Prevention and Treatment of Nerve Injuries in Shoulder Arthroplasty

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Nerve injuries during shoulder arthroplasty have traditionally been considered rare events, but recent electrodiagnostic studies have shown that intraoperative nerve trauma is relatively common.

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The brachial plexus and axillary and suprascapular nerves are the most commonly injured neurologic structures, with the radial and musculocutaneous nerves being less common sites of injury.

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Specific measures taken during the surgical approach, component implantation, and revision surgery may help to prevent direct nerve injury. Intraoperative positioning maneuvers and arm lengthening warrant consideration to minimize indirect injuries.

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Suspected nerve injuries should be investigated with electromyography preferably at 6 weeks and no later than 3 months postoperatively, allowing for primary reconstruction within 3 to 6 months of injury when indicated. Primary reconstructive options include neurolysis, direct nerve repair, nerve grafting, and nerve transfers.

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Secondary reconstruction is preferred for injuries presenting >12 months after surgery. Secondary reconstructive options with favorable outcomes include tendon transfers and free functioning muscle transfers.

Defining the proximity of the axillary nerve from defined anatomic landmarks: an in vivo magnetic resonance imaging study

BACKGROUND

The location of the axillary nerve in the shoulder makes it vulnerable to traumatic or iatrogenic injury. Cadaveric studies have reported the location of the axillary nerve but are limited because of tissue compression, dehydration, and decay. Three-Tesla (T) magnetic resonance imaging (MRI) allows high anatomic resolution of neural structures. The aim of our study was to better define the location of the axillary nerve from defined bony surgical landmarks in vivo, using MRI scan.

METHODS

Using MRI, we defined a number of anatomic points and measured the distance from these to the perineural fat surrounding the axillary nerve using simultaneous tracker lines on both images. Two observers were used.

RESULTS

A total of 187 consecutive 3-T MRI shoulder scans were included. Mean age was 57.9 years (range 18-86). The axillary nerve was located at a mean of 14.1 mm inferior from the bony glenoid at the anterior border, 11.9 mm from the midpoint, and 12.0 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P < .001), and between the anterior and posterior borders (P < .001). The axillary nerve was located at a mean of 12.6 mm medial to the humeral shaft at the anterior border, 9.9 mm at the midpoint, and 8.6 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P = .008) and between the anterior and posterior borders (P = .002). The mean distance of the axillary nerve from the anterolateral edge of the acromion was 53.3 mm (95% confidence interval [CI] 52.3, 54.2; range 33.9-76.3). The mean distance of the axillary nerve from the inferior edge of the capsule was 2.7 mm (95% CI 2.9, 3.1; range 0.3-9.9). There was a positive correlation between humeral head diameter and axillary nerve distance from the inferior glenoid (R² = 0.061, P < .001). There was a positive correlation between humeral head diameter and distance from the anterolateral edge of the acromion (R² = 0.140, P < .001).

CONCLUSION

Our study has defined the proximity of the axillary nerve from defined anatomic landmarks. The proximity of the axillary nerve to the inferior glenoid and medial humeral shaft changes as the axillary nerve passes from anterior to posterior. The distance of the axillary nerve from the anterolateral edge of the acromion remains relatively constant. Both sets of distances may be affected by humeral head size. The study has relevance to the shoulder surgeon when considering "safe zones" during arthroscopic or open surgery.

Quadrangular Space Syndrome: A Narrative Overview

OBJECTIVE

The purpose of this narrative review of the literature is to provide an overview of quadrangular space syndrome with special attention to its clinical presentation, differential diagnosis, and treatment.

METHODS

A narrative review of the English-language, peer-reviewed literature was performed using the key words "axillary nerve," "quadrangular space," "quadrilateral space," and "posterior humeral circumflex artery." Databases searched were Medline Complete, Cumulative Index to Nursing and Allied Health Literatures, and Index to Chiropractic Literature. The search period was from 1983 through January 2020.

RESULTS

There were 85 articles selected for this review. A summary and overview are provided.

CONCLUSION

Quadrangular space syndrome is an uncommon cause of shoulder pain. Clinicians should consider it as a diagnosis after ruling out more common shoulder conditions and examining other concurrent diseases.

Cadaveric evaluation of the feasibility of glenohumeral joint denervation

Purpose

To assess the feasibility of total shoulder denervation through two proposed incisions.

Methods

Total shoulder denervation was performed through an extended delta-pectoral approach and a transverse dorsal approach at the spine of the scapula. The study involved six cadavers. Course and number of articular branches from the lateral pectoral, axillary and supra-scapular nerve were documented.

Results

All shoulder joint articular branches were accessible through the proposed anterior and posterior approaches. The articular branch of the lateral pectoral nerve and supra scapular nerve were present in all the specimen. Axillary nerve articular branches were variable in number but when present anteriorly were proximal to the deltoid muscular branches and posteriorly proximal to the muscular branches to the teres minor.

Conclusion

Total glenohumeral denervation was feasible through our proposed anterior and posterior approaches. Enhanced knowledge of articular nerve branches could provide interventional targets for joint and ligament pain, with low risk of muscle weakness.

MRI evaluation of axillary neurovascular bundle: Implications for minimally invasive proximal humerus fracture fixation

Background

Percutaneous fixation of proximal humeral fractures places the axillary nerve and posterior humeral circumflex artery at risk for injury. Safe operative zones for the axillary nerve are described based on external measurements from anatomic landmarks, but no study to date has incorporated advanced imaging to help guide surgical procedures in the region of the axillary neurovascular bundle (ANVB). We sought to define the location and trajectory of the ANVB in relation to osseous landmarks using magnetic resonance imaging (MRI) measurements.

Methods

Retrospective review of 750 consecutive MRI studies was performed with 55 imaging studies meeting inclusion criteria for patient positioning, image alignment, and quality. Five measurements were performed including the distance from mid-lateral acromion to lateral ANVB, mid-lateral acromion to medial ANVB, greater tuberosity to lateral ANVB, vertical distance between inferior anatomic neck and lateral ANVB, and angle the ANVB crosses the humerus. Height, gender, and age were recorded. Analysis was performed using ANOVA and Pearson correlation tests.

Results

The lateral ANVB was below the inferior articular margin of the humeral head by an average of 12.9 ± 3.9 mm and within a 22 mm window. It was an average of 57.4 ± 5.1 mm from the lateral mid-acromion, and 34.7 ± 4.3 mm below the greater tuberosity. The angle formed by the ANVB crossing the humerus averaged 19.5 ± 3.9 degrees upward from medial to lateral. Height and gender directly impacted measurements.

Conclusions

The use of the inferior humeral head articular margin provides a radiographic landmark to aid intraoperative lateral ANVB assessment which may be helpful during percutaneous fracture fixation.

Anatomy of the nerves to the teres minor and the long head of the triceps brachii for electromyography

BACKGROUND

We investigated the branching pattern and topographic anatomy of the nerves to the teres minor (Tm) and the long head of the triceps brachii (LHT) in relation to reference lines extending between surface landmarks, to identify the innervation patterns of, and the optimal needle placement points within, the Tm and the LHT.

METHODS

The anatomical courses of the nerves to the Tm and the LHT were investigated in 37 upper limbs of fresh-frozen cadavers. Distances from the acromion to nerve penetration points, and crossing points of reference lines with the Tm and LHT were measured in 27 cadaveric upper limbs.

RESULTS

The Tm was innervated by the axillary nerve in all specimens in three patterns, and the LHT was innervated exclusively by the radial nerve. Our dissection and measurements indicate that the midpoint of the reference line from the acromion to the inferior angle of the scapula is the optimal needle insertion point for the Tm. The target point for the LHT appears to be the one-third point of the reference line from the acromion to the medial epicondyle, or the two-thirds point of the reference line from the acromion to the axillary fold.

CONCLUSIONS

We investigated the branching pattern of the nerves to the Tm and the LHT and propose optimal needle placement points for electromyography of the Tm and LHT.

Overlapping, Masquerading, and Causative Cervical Spine and Shoulder Pathology: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To assess the current literature regarding the relationship between the shoulder and the spine with regard to (1) overlapping pain pathways; (2) differentiating history, exam findings, and diagnostic findings; (3) concomitant pathology and optimal treatments; and (4) cervical spine-based etiology for shoulder problems.

METHODS

A systematic literature search was performed according to the guidelines set forth by the Cochrane Collaboration. Studies were included if they examined the clinical, anatomical, or physiological overlap between the shoulder and cervical spine. Two reviewers screened and selected full texts for inclusion according to the objectives of the study. Quality of evidence was graded using OCEBM (Oxford Center for Evidence Based Medicine) and MINORS (Methodological Index for Nonrandomized Studies) scores.

RESULTS

Out of 477 references screened, 76 articles were included for review and grouped into 4 main sections (overlapping pain pathways, differentiating exam findings, concomitant/masquerading pathology, and cervical spine-based etiology of shoulder pathology). There is evidence to suggest cervical spine pathology may cause shoulder pain and that shoulder pathology may cause neck pain. Specific examination tests used to differentiate shoulder and spine pathology are critical as imaging studies may be misleading. Diagnostic injections can be useful to confirm sources of pain as well as predicting the success of surgery in both the shoulder and the spine. There is limited evidence to suggest alterations in the relationship between the spine and the scapula may predispose to shoulder impingement or rotator cuff tears. Moreover, cervical neurological lesions may predispose patients to developing rotator cuff tears. The decision to proceed with shoulder or spine surgery first should be delineated with careful examination and the use of shoulder and spine diagnostic injections.

CONCLUSION

Shoulder and spine pathology commonly overlap. Knowledge of anatomy, pain referral patterns, shoulder kinematics, and examination techniques are invaluable to the clinician in making an appropriate diagnosis and guiding treatment. In this review, we present an algorithm for the identification and treatment of shoulder and cervical spine pathology.

Nerve and Muscle Abnormalities

Muscle atrophy in shoulders with rotator cuff tendon tears is a negative prognosticator, associated with decreased function, decreased reparability, increased retears after repair, and poorer outcomes after surgery. Muscle edema or atrophy within a neurologic distribution characterizes denervation. Because most nerve entrapments around the shoulder are not caused by mass lesions and show no nerve findings on routine MR imaging sequences, pattern of muscle denervation is often the best clue to predicting location of nerve dysfunction, which narrows the differential diagnosis and guides clinical management. The exception is suprascapular nerve compression in the spinoglenoid notch caused by a compressing cyst.

Use of the Humeral Head as a Reference Point to Prevent Axillary Nerve Damage during Proximal Fixation of Humeral Fractures: An Anatomical and Radiographic Study

Introduction

Treatment of proximal humeral fractures with plate osteosynthesis or intramedullary nail fixation in humeral shaft fractures with a proximal locking bolt carries the risk of iatrogenic injury of the axillary nerve. The purpose of this anatomical study is to define a more reliable safe zone to prevent iatrogenic axillary nerve injury using the humeral head instead of the acromion as a (radiographic) reference point during operative treatment.

Materials and methods

Anatomical dissection and labeling of the axillary nerve and branches was performed on 10 specially embalmed human specimens. Standard AP and straight lateral radiographs were made. The distances were measured indirectly from the cranial tip of the humerus to the axillary nerve on radiographs.

Results

The median distance from the cranial tip of the humerus to the axillary nerve was 52 mm. The mean number of axillary nerve branches was 3. The distances from the cranial tip of the humerus to the nerve (branch) varied from 23 to 78 mm. The median distance from the proximal (anterior) branch was 36 mm, to the second branch 47 mm, 54 mm to the third branch and 73 mm to the fourth branch. The axillary nerve moves along with the humerus in cranial and caudal direction when the subacromial space varies.

Conclusion

This study shows that the position of the axillary nerve can be better determent using the cranial tip of the humerus as a reference point instead of the acromion. Furthermore, it is unsafe to place the proximal locking bolts in the zone between 24 mm and 78 mm from the cranial tip of the humerus. The greatest chance to cause a lesion of the main branch of the axillary nerve is in the zone between 48 mm and 58 mm caudal from the tip of the humeral head.

How to cite this article

Theeuwes HP, Potters JW, Bessems JHJM, et al. Use of the Humeral Head as a Reference Point to Prevent Axillary Nerve Damage during Proximal Fixation of Humeral Fractures: An Anatomical and Radiographic Study. Strategies Trauma Limb Reconstr 2020;15(2):63–68.

Anatomy of the Scapula Applied to the Posterior Surgical Approach: Safety Parameters during Access to the Lateral Angle

Objective  The objective of this paper was to identify safety parameters in the posterior surgical approach of the scapula through a cross-sectional cadaver study.

Methods  Thirteen cadaver shoulders with no history of surgery or prior musculoskeletal dysfunction, with mean age, weight, and height of 70.1 years, 61.5 kg, and 1.64 m, respectively, were dissected. The anatomic landmark of the studied pathway (infraglenoid tubercle) and its distance to the axillary and suprascapular nerves were measured.

Results  The mean distance between the infraglenoid tubercle (IT) and the axillary nerve (AN) was 23.8 mm, and the mean distance from the IT to the suprascapular nerve (SN) was 33.2 mm.

Conclusion  The posterior approach may be considered safe through the interval between the infraspinatus and teres minor. However, caution should be taken during muscle spacing because of the short distance between the fracture site and the location of the SN and AN. These precautions help to avoid major postoperative complications.

Cadaveric Dissection of the Axillary Nerve: An Investigation of Extra-Muscular and Intra-Muscular Branching Patterns

BACKGROUND

Variations in the axillary nerve branching patterns have been reported. The aim of the study is to investigate the extra- and intra-muscular course of the axillary nerve and quantify the regional innervation of the deltoid.

METHODS

In fresh frozen specimens, the origin of the axillary nerve from the posterior cord of the brachial plexus and its extra- and intra-muscular course were identified. Muscle dimensions, branching patterns and the distance from the axillary nerve origin to major branches were measured. The weights of muscle segments supplied by major branches of the axillary nerve were recorded.

RESULTS

Twenty-three cadaveric dissections were completed. The axillary nerve bifurcated within the quadrangular space in all cases. The mean distance from the origin to bifurcation of the axillary nerve was 39 ± 13 mm; from axillary nerve bifurcation to the teres minor branch was 13 ± 6 mm; and from axillary nerve bifurcation to the middle branch of anterior division was 26 ± 11 mm. The nerve to teres minor and superior lateral brachial cutaneous nerve originated from the posterior division or common trunk in all cases. No fibrous raphe were identified separating anterior, middle and posterior deltoid segments. The anterior division of axillary nerve supplied 85 ± 4% of the deltoid muscle (by weight). The posterior division supplied 15 ± 4% of the deltoid muscle (by weight). The posterior deltoid was supplied by both anterior and posterior divisions in 91.3% of cases.

CONCLUSIONS

This study demonstrates a consistent branching pattern of the axillary nerve. The anterior division of the axillary nerve innervates all three deltoid segments in most instances (85% of the deltoid by weight). This study supports the concept of re-innervation of the anterior division alone in isolated axillary nerve injuries.

Anatomic considerations for arthroscopic glenoid reconstruction using iliac crest grafts: a radiologic study

BACKGROUND

Arthroscopic glenoid reconstruction using autografts is an advanced procedure that requires experience and preparation. Knowledge about anatomic pitfalls is therefore important to establish well-positioned portals and prevent neurovascular damage.

METHODS

We included 43 computed tomography scans from 43 patients. The distance between the tip of the coracoid process and a perpendicular line representing the anteroinferior glenoid was measured. From these results an anteroinferior working portal was designed, and the angulation needed for screw insertion to fixate a hypothetical graft was measured. In a second step, 9 patients underwent magnetic resonance imaging scans 34 ± 10 months after glenoid reconstruction, and the distance between the screw approach path and the neurovascular bundle was measured.

RESULTS

In the analyzed scans, average defect size was 23%, and the coracoid process to the anteroinferior glenoid distance was 32 ± 7 mm. We thus hypothesized that a corridor 20 to 30 mm inferior to the coracoid process would be the ideal position for a working portal. Through this portal, 85% of screws could be applied with 0° to 30° angulation. When the postoperative scans were analyzed, the distance from the neurovascular bundle showed an average of 26 ± 6 mm for the superior screw and 21 ± 5 mm for the inferior screw.

CONCLUSIONS

The ideal distance between the coracoid process and an anteroinferior working portal is 32 mm. Having established the portal, instruments should not be inserted pointing in a medial direction of the coracoid process due to the proximity of the neurovascular bundle.

Axillary Nerve Position in Humeral Avulsions of the Glenohumeral Ligament

Background

The axillary nerve is at risk during repair of a humeral avulsion of the glenohumeral ligament (HAGL).

Purpose

To measure the distance between the axillary nerve and the free edge of a HAGL lesion on preoperative magnetic resonance imaging (MRI) and compare these findings to the actual intraoperative distance measured during open HAGL repair.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 25 patients with anterior instability were diagnosed as having a HAGL lesion on MRI and proceeded to open repair. The proximity of the axillary nerve to the free edge of the HAGL lesion was measured intraoperatively at the 6-o'clock position relative to the glenoid face. Preoperative MRI was then used to measure the distance between the axillary nerve and the free edge of the HAGL lesion at the same position. Distances were compared using paired t tests and Bland-Altman analyses.

Results

The axillary nerve lay, on average, 5.60 ± 2.51 mm from the free edge of the HAGL lesion at the 6-o'clock position on preoperative MRI, while the mean actual intraoperative distance during open HAGL repair was 4.84 ± 2.56 mm, although this difference was not significant (P = .154). In 52% (13/25) of patients, the actual intraoperative distance of the axillary nerve to the free edge of the HAGL lesion was overestimated by preoperative MRI. In 36% (9/25), this overestimation of distance was greater than 2 mm.

Conclusion

The observed overestimations, although not significant in this study, suggest a smaller safety margin than might be expected and hence a substantially higher risk for potential damage. We recommend that shoulder surgeons exercise caution in placing capsular sutures in the lateral edge when contemplating arthroscopic repair of HAGL lesions, as the proximity of the nerve to the free edge of the HAGL tear is small enough to be injured by arthroscopic suture-passing instruments.

The posterior ridge of the greater tuberosity of the humerus: a suitable landmark for the posterior approach to the shoulder joint?

BACKGROUND

The purpose of this study was to evaluate the posterior ridge of the greater tuberosity, a palpable prominence during surgery, as a landmark for the posterior approach to the glenohumeral joint.

METHODS

Twenty-five human cadaveric shoulders were dissected. In 5 cases, a full-thickness rotator cuff tear was present. The posterior surgical anatomy was defined, and the distance from the ridge to the interval between the infraspinatus (IS) and teres minor (TM) muscle, the distance from the ridge to the inferior border of the glenoid (IBG), and the distance between the IS-TM interval and the IBG were determined.

RESULTS

In all specimens, a prominent ridge on the posterior greater tuberosity lateral to the articular margin could be identified. The IS-TM interval was located, on average, 3 mm proximal to this ridge. The IS-TM interval corresponded to a point 5 mm proximal to the IBG. In all shoulders, the ridge was located, on average, 8 mm proximal to the IBG. The plane of the IS-TM interval showed a vertically oblique direction.

CONCLUSION

The posterior ridge of the greater tuberosity is a suitable landmark to locate the internervous plane between the IS and TM and should not be crossed distally. Unlike other landmarks, the ridge moves with the humeral head, making it is less dependent on the patient's size, sex, and arm position and the quality of the rotator cuff. The ridge is always located proximal to the insertion of the TM and IBG.

Understanding the Importance of the Teres Minor for Shoulder Function: Functional Anatomy and Pathology

Although the teres minor is often overlooked in a normal shoulder, it becomes a key component in maintaining shoulder function when other rotator cuff tendons fail. The teres minor maintains a balanced glenohumeral joint and changes from an insignificant to the most significant external rotator in the presence of major rotator cuff pathology. The presence or absence of the teres minor provides prognostic information on the outcomes of reverse total shoulder arthroplasty and tendon transfers. Clinical tests include the Patte test, the Neer dropping sign, the external rotation lag sign, and the Hertel drop sign. Advanced imaging of the teres minor can be used for classification using the Walch system. Understanding the function and pathology surrounding the teres minor is paramount in comprehensive management of the patient with shoulder pathology. Appropriate clinical examination and imaging of the teres minor are important for preoperative stratification and postoperative expectations.

Effect of patient positioning in axillary nerve safety during arthroscopic inferior glenohumeral ligament plication

PURPOSE

To evaluate the risk of injuring the axillary nerve during an inferior glenohumeral ligament (IGHL) plication and finding out whether shoulder position (either beach chair position or lateral decubitus position) has any effect in this risk.

METHODS

The axillary nerve (AN) was identified through a 3-cm posterior incision in 12 cadaveric shoulders. Under arthroscopic visualization, a curved indirect suture-passing device was placed through the posterior and anterior bands of the IGHL. The distances between the device and the AN were measured with the shoulder specimen placed at simulated lateral decubitus position and beach chair position.

RESULTS

There were no cases of nerve injury nor the suture-passing device came closer than 10 mm to the nerve. There was an increase in the injury risk to the AN when inserting the device at the posterior band of the IGHL in the beach chair position [median 13 mm (range 10-21 mm)] compared to the risk in the lateral decubitus position [22.5 mm (20-26 mm), significant differences, p < 0.001]. When the device was inserted at the anterior band of the IGHL, there were no significant differences (n.s.) [lateral decubitus position: 18 mm (14-24 mm) vs. 16 mm (13-18 mm)]. When comparing differences between bands, there were no differences in the beach chair position, but the risk was lower for the posterior band in the lateral decubitus position (p < 0.001).

CONCLUSIONS

During plication of the posterior band of the IGHL, the risk is higher if the procedure is performed in the beach chair position. The posterior plication is safer than the anterior plication in lateral decubitus position.

CLINICAL RELEVANCE

This study helps the surgeon to better understand the proximity of the nerve to the IGHL and to highlight that the risk of nerve injury during capsular plication might be reduced in the lateral decubitus position.

Effect of scapular external rotation on the axillary nerve during the arthroscopic Latarjet procedure: an anatomical investigation

PURPOSE

The first purpose of this study is to measure the distance between the axillary nerve and the exit point of K-wires placed retrograde through the glenoid in the setting of an arthroscopic Latarjet procedure. The second objective is to evaluate whether manual external rotation of the scapula alters that distance.

METHODS

In seven fresh-frozen specimens, two 2.0-mm K-wires were drilled through the glenoid using an arthroscopic Latarjet retrograde glenoid guide. These were drilled into the glenoid at the 7- and 8-o'clock positions (right shoulders) and at the 4- and 5-o'clock positions (left). K-wires were oriented parallel to the glenoid articular surface and perpendicular to the long superoinferior axis of the glenoid, 7 mm medial to the joint surface. Two independent evaluators measured the distances between the axillary nerve and the exit point of the K-wires in the horizontal plane (AKHS for the superior K-wire and AKHI for the inferior K-wire) and in the vertical plane (AKV). Measurements were taken with the scapula left free and were repeated with the scapula placed at 15° and 30° of external rotation.

RESULTS

With the scapula left free, scapular external rotation was 34° ± 2.3°. In this position, the AKHS was 2.5 ± 1.6, 6.3 ± 1.2 mm at 15° of external rotation (ER) and 11.4 ± 1.4 mm at 30° ER. The AKHI distance was 0.37 ± 1.6, 3.4 ± 1.4 and 10.6 ± 2.1 mm, respectively, for the scapula left free, at 15° ER and 30° of ER. The AKV distances were, respectively, 0.12 ± 0.2, 4.9 ± 1.6 and 9.9 ± 1.7 mm. The increase in all distances was statistically significant (p < 0.001).

CONCLUSION

Increasing scapular external rotation significantly increases the distance between the axillary nerve and the exit point of the K-wires, increasing the margin of safety during this procedure. Therefore, increased external rotation of the scapula could be an effective tool to decrease the risk of iatrogenic axillary nerve injury.

LEVEL OF EVIDENCE

Cadaveric study, Level V.

Anatomical Relationship of the Axillary Nerve to the Pectoralis Major Tendon Insertion

Axillary nerve injury is a risk of the deltopectoral approach to the proximal humerus. The anterior motor branch is potentially vulnerable during subdeltoid dissection. Insertion of the pectoralis major tendon is an easily identifiable landmark on the humerus. This anatomical study explored whether the superior aspect of the pectoralis major tendon is a useful landmark for localizing the anterior motor branch of the axillary nerve as it travels under the lateral and anterior deltoid muscle. A total of 30 fresh-frozen human bilateral cadaveric upper extremities were examined. A deltopectoral approach was used to expose the pectoralis major tendon insertion and the anterior motor branch of the nerve under the deltoid muscle. The distance between the nerve as it crossed the posterolateral humerus and superior border of the pectoralis major tendon was measured. The axillary nerve was a mean 3.2 mm (range, 0-8 mm) distal to the superior border of the pectoralis major tendon insertion. No significant differences were observed in this anatomical relationship with the shoulder in abduction or external rotation. The nerve was not proximal to the superior border of the pectoralis major tendon in any specimen. The superior border of the pectoralis major tendon insertion represents a reliable landmark for the anterior motor branch of the axillary nerve as it travels under the deltoid muscle. The nerve is located at the level of the proximal centimeter of the pectoralis major tendon. Appreciation of this relationship may decrease risk of injury to the nerve when using a deltopectoral approach. [Orthopedics. 2017; 40(3):e460-e464.].

Rotator cuff-sparing approaches for glenohumeral joint access: an anatomic feasibility study

BACKGROUND

The deltopectoral approach for total shoulder arthroplasty can result in subscapularis dysfunction. In addition, glenoid wear is more prevalent posteriorly, a region difficult to access with this approach. We propose a posterior approach for access in total shoulder arthroplasty that uses the internervous interval between the infraspinatus and teres minor. This study compares this internervous posterior approach with other rotator cuff-sparing techniques, namely, the subscapularis-splitting and rotator interval approaches.

METHODS

The 3 approaches were performed on 12 fresh frozen cadavers. The degree of circumferential access to the glenohumeral joint, the force exerted on the rotator cuff, the proximity of neurovascular structures, and the depth of the incisions were measured, and digital photographs of the approaches in different arm positions were analyzed.

RESULTS

The posterior approach permits direct linear access to 60% of the humeral and 59% of the glenoid joint circumference compared with 39% and 42% for the subscapularis-splitting approach and 37% and 28% for the rotator interval approach. The mean force of retraction on the rotator cuff was 2.76 (standard deviation [SD], 1.10) N with the posterior approach, 2.72 (SD, 1.22) N with the rotator interval, and 4.75 (SD, 2.56) N with the subscapularis-splitting approach. From the digital photographs and depth measurements, the estimated volumetric access available for instrumentation during surgery was comparable for the 3 approaches.

CONCLUSION

The internervous posterior approach provides greater access to the shoulder joint while minimizing damage to the rotator cuff.

Variations in the Innervation of the Long Head of the Triceps Brachii: A Cadaveric Investigation

BACKGROUND

Some leading anatomy texts state that all three heads of the triceps brachii are innervated by the radial nerve. The posterior cord of the brachial plexus bifurcates to terminate as the radial and axillary nerves. Studies have noted the presence of axillary innervation to the long head of the triceps brachii muscle, patterns different from the classic exclusive radial nerve supply. An understanding of these variations may assist the clinician in the assessment of shoulder weakness and in preoperative and operative planning of radial and axillary neuropathies.

QUESTIONS/PURPOSE

We aimed to further investigate, in cadaver dissections, the prevalence of axillary nerve contribution to the innervation of the long head of the triceps brachii.

METHODS

We performed bilateral brachial plexus dissections on 10 embalmed cadavers combining anterior axillary and posterior subscapular approaches. Two additional unilateral cadaveric brachial plexuses were dissected. The posterior cords were fully dissected from the roots distally. The radial and axillary nerves were followed to their muscle insertion points, the dissections were photographed, and the length of branching segments were measured.

RESULTS

Of the 10 paired cadavers dissected (20 specimens), in only one of the 10 cadavers was the classic innervation pattern of radial nerve observed. The other nine cadavers had varying patterns of radial and axillary nerve innervation, The observed patterns were radial and axillary (dual) on one side with radial alone on the other, dual innervation bilaterally, or axillary with contralateral radial innervation. The two additional unilateral dissected specimens were innervated exclusively by the axillary nerve.

CONCLUSIONS

Gross and surgical anatomy sources state that the radial nerve is the sole nerve supply to the long head of the triceps. In our study sample, pure radial innervation of the long head of the triceps brachii was not the predominant nerve pattern. We found four other studies that looked at axillary innervation of the long head of the triceps; of the 62 total cadaver shoulders examined in those studies, 71% were found to have nonclassic innervation patterns. Nonclassic patterns may include purely axillary, dual, or posterior cord innervation to the long head of the triceps, and may account for the majority of innervation to the long head of the triceps. These are similar to our findings.

CLINICAL RELEVANCE

Understanding the innervation of the long head of the triceps and variations in axillary nerve course is critical to the clinical diagnosis of injury, surgical treatment options, and rehabilitation of axillary nerve injuries. With this information, the practitioner may have additional surgical options, clearer rationales for clinical situations, and explanations for patient outcomes.

Treatment of the Open Glenohumeral Joint with the Anterior Deltoid Muscle Flap

Upper extremity reconstruction is most often encountered in trauma patients. Although the rate of complications from elective orthopedic procedures remains relatively low, these complications are oftentimes in the form of open joints or joint infections that can be devastating. Classically, wounds of the shoulder girdle have been treated with large muscles such as the pectoralis major, pectoralis minor, and latissimus dorsi. Flaps more local to the area including the deltoid muscle flap have been overlooked due to their small size. Despite its size, the anterior deltoid can be used for shoulder girdle reconstruction with minimal functional deficit and allows for reconstruction of the glenohumeral joint without sacrifice of the larger muscles of the upper trunk. This study reports a case of a chronic shoulder girdle wound and successful management with the use of an anterior deltoid muscle flap.

Effect of Teres Minor Fatty Infiltration on Rotator Cuff Repair Outcomes

PURPOSE

To observe changes in fatty infiltration (FI) of the teres minor without tear of the teres minor in a postoperative magnetic resonance imaging and to evaluate the influence of FI of the teres minor in the clinical outcomes of rotator cuff repair.

METHODS

Of 816 patients who underwent rotator cuff repair, 51 (6.3%) had FI of the teres minor without tear involvement and 30 cases were available for postoperative magnetic resonance imaging. FI and functional outcome scores were assessed and compared with the control group that had no FI of the teres minor selected by a propensity score matching.

RESULTS

FI of the teres minor was observed in various degrees (grade 1 in 9, grade 2 in 9, grade 3 in 6, and grade 4 in 6). The degree of FI was not related to the amount of tendon involvement of a rotator cuff tear (P = .240). All postoperative functional outcome scores (12.6 ± 1.2 months; range, 11-17), including pain visual analog scale, Simple Shoulder Test, and American Shoulder and Elbow Surgeons Score, significantly improved (all P < .001), and there were no significant differences compared with that of the control group. In most of the cases, FI of the teres minor was unchanged (P = .317).

CONCLUSIONS

FI of the teres minor without tear involvement can be observed in a rotator cuff tear as a possibly incidental finding of unknown clinical significance. Its cause has not been determined, and it appears that FI of the teres minor does not appear to improve, at least at the 1-year follow-up. Nevertheless, the functional outcomes of the repair were successful in our study; therefore, rotator cuff repair can be performed without a great deal of concern in the presence of FI in the teres minor.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Distribution of the axillary nerve to the subacromial bursa and the area around the long head of the biceps tendon

PURPOSE

Patients with a shoulder disorder often complain of pain on the anterior or lateral aspect of the shoulder. Such pain has been thought to originate from the suprascapular nerve. However, taking into consideration the distinctive course of the axillary nerve, the axillary nerve is likely to supply branches to the structure around the shoulder joint. This study was conducted to clarify the division, course, and distribution of the branches which originate from the axillary nerve and innervate structures around the shoulder joint.

METHODS

The division, course, and distribution of the branches which originate from the axillary nerve and innervate structures around the shoulder joint were examined macroscopically by dissecting 20 shoulders of 10 adult Japanese cadavers.

RESULTS

The thin branches from the anterior branch of the axillary nerve were distributed to the subacromial bursa and the area around the long head of the biceps tendon. The branches from the main trunk of the axillary nerve or the branch to the teres minor muscle were distributed to the infero-posterior part of the shoulder joint.

CONCLUSION

The pain on the anterior or lateral aspect of the shoulder, which has been thought to originate from the suprascapular nerve, might be related to the thin branches which originate from the axillary nerve and innervate the subacromial bursa and the area around the long head of the biceps tendon.

CLINICAL RELEVANCE

These results would be useful to consider the cause of the shoulder pain or to prevent the residual pain after the biceps tenodesis.

Anatomy of axillary nerve and its clinical importance: a cadaveric study

INTRODUCTION

Axillary nerve is one of the terminal branches of posterior cord of brachial plexus, which is most commonly injured during numerous orthopaedic surgeries, during shoulder dislocation & rotator cuff tear. All these possible iatrogenic injuries are because of lack of awareness of anatomical variations of the nerve. Therefore, it is very much necessary to explore its possible variations and guide the surgeons to enhance the better clinical outcome by reducing the risk and complications.

MATERIALS AND METHODS

Twenty five cadavers (20 Males & 05 Females) making 50 specimens including both right and left sides were dissected as per standard dissection methods to find the origin, course, branches, distribution & exact location of the nerve beneath the deltoid muscle from important landmarks like: posterolateral aspect of acromion process, anteromedial aspect of tip of coracoid process, midpoint of deltoid muscle insertion (deltoid tuberosity of humerus) and from the midpoint of vertical length of deltoid muscle. The measurements were recorded and tabulated.

STATISTICAL ANALYSIS

The measurements were entered in Microsoft excel and mean, proportion, standard deviation were calculated by using SPSS 16th version.

RESULTS

The axillary nerve was found to take origin from the posterior cord of brachial plexus (100%) dividing into anterior & posterior branches in Quadrangular space (88%) and supply deltoid muscle mainly. It also gave branches to teres minor muscle, shoulder joint capsule & superolateral brachial cutaneous nerve (100%). This study concluded that the mean distance of axillary nerve from the - anteromedial aspect of tip of coracoid process, posterolateral aspect of acromion process, midpoint of deltoid insertion & from the midpoint of vertical length of deltoid muscle measured to be (in cm) as 3.56±0.51, 7.4±0.99, 6.7±0.47 & 2.45±0.48 respectively. The mean vertical distance of entering point of axillary nerve from the anterior upper, mid middle upper & posterior upper deltoid border found to be (in cm): 4.94±0.86, 5.14±0.90 & 5.44±0.95 respectively and the horizontal anterior & horizontal posterior mean distance being 4.54±0.65 & 3.22±0.53 respectively. The mean height, mean width & mean depth of Quadrangular space measured to be (in cm): 2.23±0.40, 2.19±0.22 & 1.25±0.14 respectively.

CONCLUSION

The findings were found to be highly significant when males were compared with females but not significant when sides (right & left) were compared.

Axillary nerve position in the anterosuperior approach of the shoulder: a cadaveric study

OBJECTIVE

To determine the distance between the axillary nerve and the antero-lateral (AL) edge of the acromion, its anatomical variability and relationship to humeral length and body height.

METHODS

Twenty-two shoulders were dissected. The anterosuperior (AS) approach was used; the deltoid was detached from the acromion and the distance between the AL portion and the axillary nerve was measured and submitted to statistical analysis.

RESULTS

The distance varied from 4.3 to 6.4 cm (average 5.32 ± 0.60 cm). The axillary nerve distance increased as the humeral size (p<0.05) and the height of each cadaver increased. However, the correlation with the specimens height was not significant (p=0.24).

CONCLUSIONS

The distance between the acromion and the axillary nerve on the AS approach was 5.32 ± 0.60 cm in both shoulders, and increasing the humeral length there is also an increase in the axillary nerve distance. Level of Evidence IV, Case Series - Anatomic Study.

Complications of shoulder arthroscopy

Over the past 20 to 30 years, arthroscopic shoulder techniques have become increasingly popular. Although these techniques have several advantages over open surgery, surgical complications are no less prevalent or devastating than those associated with open techniques. Some of the complications associated with arthroscopic shoulder surgery include recurrent instability, soft-tissue injury, and neurapraxia. These complications can be minimized with thoughtful consideration of the surgical indications, careful patient selection and positioning, and a thorough knowledge of the shoulder anatomy. Deep infection following arthroscopic shoulder surgery is rare; however, the shoulder is particularly susceptible to Propionibacterium acnes infection, which is mildly virulent and has a benign presentation. The surgeon must maintain a high index of suspicion for this infection. Thromboemoblic complications associated with arthroscopic shoulder techniques are also rare, and studies have shown that pharmacologic prophylaxis has minimal efficacy in preventing these complications. Because high-quality studies on the subject are lacking, minimal evidence is available to suggest strategies for prevention.

[Arthroscopic nerve release and decompression of ganglion cysts around the shoulder joint]

OBJECTIVE

Arthroscopic visualisation and release of nerves around the shoulder, decompression of ganglion cysts.

INDICATIONS

Arthroscopic treatment of nerve entrapment syndromes around the shoulder (suprascapular nerve, axillary nerve). Arthroscopic visualisation and release of osseous or ligamentous structures causing nerve entrapment. Arthroscopic decompression and resection of periglenoid ganglion cysts. Arthroscopic release of concomitant lesions (labrum, rotator cuff, biceps).

CONTRAINDICATIONS

No clinical or neurological evidence for nerve entrapment syndrome. Lack of conditions for a complex arthroscopic procedure (technique of visualisation, instrumentation, knowledge of specific neuroanatomy).

SURGICAL TECHNIQUE

Diagnostic arthroscopy, decompression/resection of ganglion cyst. Visualisation and decompression of nerve. Detection and fixation of concomitant pathologies.

POSTOPERATIVE TREATMENT

Immobilisation in sling during the day after the operation. Actively assisted and active mobilisation of shoulder controlled by discomfort level. Manual lymph drainage starting on postoperative day 1. Sling and further rehabilitation according to treatment of concomitant lesions.

Surgical anatomy of the axillary nerve branches to the deltoid muscle

Variations in the innervation of the posterior deltoid muscle by the anterior branch of the axillary nerve have been reported. The objective of this study is to clarify the anatomy of the axillary nerve branches to the deltoid muscle. One hundred and twenty-nine arms (68 right and 61 left) from 88 embalmed cadavers (83 male and 46 female) were included in the study. The anterior and posterior branches of the axillary nerve were identified and their lengths were measured from the point of emergence from the axillary nerve to their terminations in the deltoid muscle. In all cases, the axillary nerves split into two branches (anterior and posterior) within the quadrangular space and none split within the deltoid muscle. In all specimens, the anterior and middle parts of the deltoid muscle received their nerve supplies from the anterior branch of the axillary nerve. The posterior part of the deltoid muscle was supplied only by the anterior branch of the axillary nerve in 2.3% of the specimens, from the posterior branch in 8.5%, and from both branches in 89.1%. There were two sub-branches of the anterior branch in 4.7% of the specimens. The anterior branch of the axillary nerve supplied not only the anterior and middle parts of the deltoid muscle but also the posterior part in most cases (91.5%).

Injury to the axillary nerve after reverse shoulder arthroplasty: an anatomical study

BACKGROUND

Subclinical neurological lesions after reverse shoulder arthroplasty are frequent, mainly those involving the axillary nerve. One of the major reported risk factors is postoperative lengthening of the arm. The purpose of this study was to evaluate the anatomical relationship between the axillary nerve and prosthetic components after reverse shoulder arthroplasty. The study hypothesis was that inferior overhang of the glenosphere relative to glenoid could put this nerve at risk.

MATERIAL AND METHODS

Eleven fresh frozen shoulder specimens were dissected after having undergone reverse shoulder arthroplasty using a classic deltopectoral approach.

RESULTS

The mean distance from the inferior border of the glenoid to the inferior edge of the glenosphere was 6.0±4.3mm (range, 1.0 to 16.2mm). The axillary nerve was never closer than 15mm to the glenosphere. The main anterior branch of the axillary nerve was in close contact with the posterior metaphysis or humeral prosthetic implant. The mean distance between the nerve and the humeral implants was 5.2±2.1mm (range, 2.0 to 8.1mm).

CONCLUSIONS

The proximity of the axillary nerve to the posterior metaphysis or humeral implants may be a risk factor for axillary nerve injury after reverse shoulder arthroplasty.

CLINICAL RELEVANCE

This study quantifies the proximity of the axillary nerve to the implant after reverse shoulder arthroplasty.

LEVEL OF EVIDENCE

Basic science study, cadaver study.

Prediction of the location of the anterior branch of the axillary nerve, using correlations with physical factors: a cadaveric study

BACKGROUND

Although axillary nerve injury is a catastrophic surgical complication, there is little data for precise prediction of the location of that nerve's anterior branch. To address that, the authors searched for a useful correlation between the acromion-axillary nerve distance (AAND) and one or more physical factors.

METHODS

The heights, humeral lengths, AAND, and axillary nerve indexes (ANI: ratio between AAND and humeral length) of 25 male and 20 female cadavers were determined. Any gender differences in the mean measurements were determined. The correlations of each AAND with height, humeral length, and ANI were determined. The authors determined that using the ANI and the humeral length allowed the shortest prediction of the AAND.

RESULTS

The mean AAND, cadaver height, and humeral length were 6.5 ± 0.8, 164.9 ± 10.0, and 33.5 ± 2.7 cm, respectively. An independent t test revealed significant gender differences in the mean AAND (P = .003), height (P = .000), and humeral length (P = .000), but not in the mean ANI (P = .564). The Pearson coefficients for the associations of the AAND with height (r = .767), humeral length (r = .797) and ANI (r = .732) demonstrated strong correlations (P < .001), especially with humeral length. The use of the ANI with the humeral length yielded the shortest predictions of AAND, with a 97.8% probability of safety.

CONCLUSION

There is a strong correlation between AAND and humeral length. In clinical practice, humeral length and ANI are useful for predicting the location of the anterior branch of the axillary nerve, when the arm is positioned at the side in neutral rotation.

Reconstruction of shoulder abduction by multiple nerve fascicle transfer through posterior approach

PURPOSE

To evaluate the feasibility and clinical efficacy of multiple nerve fascicle transfer through posterior approach for reconstruction of shoulder abduction in patients with C5 or upper brachial plexus injury.

METHODS

11 patients (aged between 17 and 56 years) with dysfunction of shoulder abduction post C5 or upper brachial plexus injury were recruited in this study. Among them, four out of 11 patients also had dysfunction of elbow flexion simultaneously. The duration from injury to the surgery ranged from 4 to 12 months, with an average of 6.7 months. The affected shoulder joints showed abduction, extension and elevation dysfunction, but the muscle strength of shoulder shrugging and elbow extension was graded to M4 or higher. Accessory nerve was transferred to the suprascapular nerve and triceps muscle was branched to the axillary nerve through posterior approach. Ulnar fascicle was transferred to the motor branches of biceps for the 4 patients involved with elbow flexion dysfunction.

RESULTS

Ten out of 11 cases were followed-up for 15-36 months. Neo-potential of deltoid and supraspinatus/infraspinatus was documented at 4-5 months post surgery. Shoulder abduction (and elbow flexion) was reanimated at 4-8 months post surgery. Significant improvement was observed at 15-36 months post surgery, shoulder abduction regained to 40-160° (mean: 92.5°), muscle strength of supraspinatus/infraspinatus and deltoid were graded to M3-M5 (mean: 4.0 and 4.1); 3 cases muscle strength of elbow flexion was graded from M4 to M5- (mean: 4.4) with 1 case loss. Shoulder shrugging of trapezius was graded to M5 in 5 cases, M5- in 2 cases, M4 in 2 cases and M3 in 1 case (mean: 4.5). All cases showed normal elbow extension and muscle strength of triceps (M5).

CONCLUSION

It is feasible to carry out multiple nerve fascicle transfers for early reconstruction of shoulder abduction by posterior approach. Patients who received this procedure achieved good functional recovery and their donor site morbidity/injury was minimal.

An association between the inferior humeral head osteophyte and teres minor fatty infiltration: evidence for axillary nerve entrapment in glenohumeral osteoarthritis

BACKGROUND

Glenohumeral osteoarthritis often results in inferior humeral osteophytes. Anatomic studies suggest that the axillary neurovascular bundle is in close proximity to the glenohumeral capsule. We therefore hypothesize that an inferior humeral osteophyte of sufficient magnitude could encroach on the axillary nerve and result in measurable fatty infiltration of the teres minor muscle.

MATERIALS AND METHODS

Preoperative magnetic resonance imaging studies of 91 consecutive arthritic shoulders were retrospectively reviewed. Two cohorts were established based on the presence of a humeral osteophyte. The distances from the axillary neurovascular bundle to various osseous structures were measured using calibrated software. Objective quantitative measurements of the degree of fatty infiltration of the teres minor muscles were obtained with image analysis software. Results were compared between cohorts.

RESULTS

The distance between the inferior humerus and axillary neurovascular bundle was inversely correlated to the size of the inferior humeral osteophyte (ρ = -0.631, P < .001). Fatty infiltration of the teres minor was greater when an inferior osteophyte was present (11.9%) than when an osteophyte was not present (4.4%) (P = .004). A statistically significant correlation between the size of the humeral head spur and quantity of fat in the teres minor muscle belly (ρ = 0.297, P = .005) was identified.

CONCLUSION

These data are consistent with our hypothesis that the axillary nerve may be entrapped by the inferior humeral osteophyte often presenting with glenohumeral osteoarthritis. Entrapment may affect axillary nerve function and lead to changes in the teres minor muscle. Axillary neuropathy from an inferior humeral osteophyte may represent a contributing and treatable cause of pain in patients with glenohumeral osteoarthritis.

Teres minor muscle and related anatomy

BACKGROUND

The purpose of this study was to describe the complex anatomy surrounding the teres minor muscle.

METHODS

Thirty-one cadaveric human shoulders were dissected. Qualitative fascial and neurovascular anatomy were described. Location of motor nerves to teres minor were measured in reference to local anatomy.

RESULTS

Fascial anatomy of the posterior shoulder had 2 distinct and equally common variants, 1 of which demonstrated a stout, inflexible fascial compartment enveloping the teres minor muscle. The other had a continuous fascia enveloping both the infraspinatus and teres minor muscles. In both variants, the primary nerve to teres minor traveled around a fascial sling, becoming sub-fascial at an average of 44 mm (range, 25-68) medial to the teres minor's insertion. The nerve took its most angulated course as it entered the fascial sling. Smaller accessory innervation of teres minor began, on average, 30 mm (range, 15-48) medial to the muscle's lateral insertion. None of the accessory motor nerves coursed deep to the fascial sling nor to the distinct teres minor fascial compartment.

CONCLUSION

A stout fascial sling may be the potential site of greatest compression and tethering of the primary motor nerve to teres minor. Additional lateral accessory motor nerves to teres minor remained extra-fascial and took a less angulated path. Half of the shoulders demonstrated a separate teres minor fascial compartment. An improved understanding of the fascial anatomy and innervation pattern of the teres minor muscle may help clinicians who treat patients with symptomatic isolated teres minor muscle atrophy.

Ganglion cyst of the spinoglenoid notch: comparison between SLAP repair alone and SLAP repair with cyst decompression

BACKGROUND

Some authors have described the ganglion cyst of the spinoglenoidal notch as related to repetitive overhead activities and labral tear caused by trauma, while others have explained lesions of the capsulolabral complex and ganglion cysts to have separate pathologies. The purpose of this study is to compare clinical and radiological outcomes between 2 groups: 1 with superior labrum anterior and posterior (SLAP) repair only and the other with SLAP repair and cyst decompression prospectively.

MATERIALS AND METHODS

From August 2000 to March 2007, 28 patients matching the inclusion criteria were selected for the study. They were divided into 2 groups: 1 who received SLAP repair and the other with concomitant SLAP repair and cyst decompression. A visual analogue scale (VAS) and Rowe and Constant scores were used to make evaluation. Preoperative magnetic resonance images (MRIs) of 2 patient groups were compared with 2 follow-up MRIs taken 3 months after the operation and at final follow-up.

RESULTS

Mean VAS and Constant and Rowe scores in groups I and II improved significantly from mean preoperative score compared to last follow-up score; however, there was no statistically significant difference between the 2 groups (P > .05). Preoperative MRI and arthroscopy revealed type II SLAP lesions and a type V lesion, respectively, as accompanying lesions in 24 cases.

CONCLUSION

The hypothesis stating 1-way valve mechanism of SLAP lesion as an initial cause of ganglion cysts has been proved indirectly in this study. Furthermore, direct decompression of the cyst does not lead to different results.

Anterior deltopectoral approach for axillary nerve neurotisation

PURPOSE

To report outcome of axillary nerve neurotisation for brachial plexus injury through the anterior deltopectoral approach.

METHODS

Nine men aged 20 to 52 (mean, 27.8) years with brachial plexus injury underwent axillary nerve neurotisation through the anterior deltopectoral approach. Three of the patients had complete avulsion of C5-T1 nerve roots. The remaining 6 patients had brachial plexus injury of C5-C6 nerve roots, with associated subluxation of the glenohumeral joint, atrophy of the supraspinatus, deltoid and elbow flexors. They had no active shoulder abduction, external rotation, and elbow flexion. The pectoralis major and minor were cut and/or retracted to expose the underlying infraclavicular plexus. The axillary nerve was identified with respect to the available donor nerves (long head of triceps branch, thoracodorsal nerve, and medial pectoral nerve). In addition to the axillary nerve neurotisation, each patient had a spinal accessory nerve transferred to the suprascapular nerve for better shoulder animation.

RESULTS

Patients were followed up for 24 to 30 (mean, 26) months. In the 3 patients with C5-T1 nerve root injuries, the mean active abduction and external rotation were 63 and 20 degrees, respectively, whereas the mean abduction strength was M3 (motion against gravity). In the 6 patients with C5-C6 nerve root injuries, the mean active abduction and external rotation were 133 and 65 degrees, respectively, whereas the strength of the deltoids and triceps was M5 (normal) in all. In 4 patients with the pectoralis major cut and repaired, the muscle regained normal strength.

CONCLUSION

The anterior deltopectoral approach enabled easy access to all available donor nerves for axillary nerve neurotisation and achieved good outcomes.

Glenohumeral joint preservation: a review of management options for young, active patients with osteoarthritis

The management of osteoarthritis of the shoulder in young, active patients is a challenge, and the optimal treatment has yet to be completely established. Many of these patients wish to maintain a high level of activity, and arthroplasty may not be a practical treatment option. It is these patients who may be excellent candidates for joint-preservation procedures in an effort to avoid or delay joint replacement. Several palliative and restorative techniques are currently optional. Joint debridement has shown good results and a combination of arthroscopic debridement with a capsular release, humeral osteoplasty, and transcapsular axillary nerve decompression seems promising when humeral osteophytes are present. Currently, microfracture seems the most studied reparative treatment modality available. Other techniques, such as autologous chondrocyte implantation and osteochondral transfers, have reportedly shown potential but are currently mainly still investigational procedures. This paper gives an overview of the currently available joint preserving surgical techniques for glenohumeral osteoarthritis.

Arthroscopic trans-capsular axillary nerve decompression: indication and surgical technique

Symptomatic axillary nerve compression is rare yet results in debilitating pain, weakness, and decreased athletic performance in some patients. If nonoperative modalities fail, surgical intervention is necessary to reduce symptoms and avoid functional decline. Traditionally, open techniques have been described to decompress the axillary nerve and are reported to provide satisfactory results. Similar to suprascapular nerve decompression, recent advances have provided the opportunity to develop all-arthroscopic axillary nerve decompression techniques. Although direct comparisons between open and arthroscopic techniques do not exist, arthroscopic axillary nerve decompression may provide some benefits over open techniques. Therefore we present a technique and early results for all-arthroscopic trans-capsular axillary nerve decompression.