The anatomic branch pattern of the axillary nerve

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.

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.

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

➤

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

➤

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.

➤

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.

➤

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.

➤

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.

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.

Sensory innervation of the human shoulder joint: the three bridges to break

BACKGROUND

Painful shoulders create a substantial socioeconomic burden and significant diagnostic challenge for shoulder surgeons. Consensus with respect to the anatomic location of sensory nerve branches is lacking. The aim of this literature review was to establish consensus with respect to the anatomic features of the articular branches (ABs) (1) innervating the shoulder joint and (2) the distribution of sensory receptors about its capsule and bursae.

MATERIALS AND METHODS

Four electronic databases were queried, between January 1945 and June 2019. Thirty original articles providing a detailed description of the distribution of sensory receptors about the shoulder joint capsule (13) and its ABs (22) were reviewed.

RESULTS

The suprascapular, lateral pectoral, axillary, and lower subscapular nerves were found to provide ABs to the shoulder joint. The highest density of nociceptors was found in the subacromial bursa. The highest density of mechanoreceptors was identified within the insertion of the glenohumeral ligaments. The most frequently identified innervation pattern comprised 3 nerve bridges (consisting of ABs from suprascapular, axillary, and lateral pectoral nerves) connecting the trigger and the identified pain generator areas rich in nociceptors.

CONCLUSION

Current literature supports the presence of a common sensory innervation pattern for the human shoulder joint. Anatomic studies have demonstrated that the most common parent nerves supplying ABs to the shoulder joint are the suprascapular, lateral pectoral, and axillary nerves. Further studies are needed to assess both the safety and efficacy of selective denervation of the painful shoulders, while limiting the loss of proprioceptive function.

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.

Arthroscopic transosseous rotator cuff repair: how to avoid damaging the axillary nerve-a cadaveric study

INTRODUCTION

Arthroscopic transosseous rotator cuff repair can be performed with an external guide, although the proximity to the axillary nerve raises safety concerns. The aim of this study is to determine the safety of different drilling angles regarding the axillary nerve.

MATERIALS AND METHODS

We performed a bone tunnel in the greater tuberosity in 17 fresh frozen shoulders, using an external guide at four different angles: 40°, 50°, 60°, and 70°. At each angle, we measured the distance between the drill and the axillary nerve, the distance from the acromion to the skin incision point, and the perimeter of the arm at the axilla.

RESULTS

The distance to the axillary nerve was safe with the guide at an angle of 40°, 50° and 60°, but not at 70° (p = 0.001). We found significant differences between all four angles (p < 0.05). Regression analysis demonstrated the influence of the guide angle in all measurements assessed (p < 0.001). There was no association between the measurements taken and the axillary perimeter (p > 0.5).

CONCLUSIONS

Arthroscopic transosseous rotator cuff repair with an external guide does not pose a risk for the axillary nerve using angles of 60° or less.

Selective Glenohumeral external rotation deficit - sequelae of post-ORIF deltoid adhesions after treatment of the proximal humerus fracture

Background

The deltopectoral approach is commonly used for plate stabilization of proximal humerus fracture. Although adhesions between the deltoid, plate, and humerus are common sequelae of plate ORIF, little is known about their effect on the range of movement and a function of the shoulder. To confirm their impact, the preoperative and intraoperative evaluation of the range of motion (ROM) was measured during the sequential arthroscopic release of adhesions, with special regard to external rotation. Postoperative ROM and subjective shoulder function were also evaluated.

Methods

Eighteen patients treated with ORIF of the proximal humerus were scheduled to the unified arthroscopic procedures comprising sequential limited subacromial bursectomy, removal of the adhesions between the deltoid, plate, and humerus, as well as the plate removal. The ROM of the operated and opposite shoulders were assessed before surgery, intraoperatively and after a minimum two-year follow-up, with special regard to external rotation in adduction (AddER) and abduction (AbdER). Besides, the Constant-Murley score and Subjective Shoulder Value (SSV) were evaluated before a plate removal and after a minimum two-year follow-up after the surgery.

Results

Deltoid adhesion release correlated with considerable and statistically significant improvement of AddER (p < 0.0002) but not with the intraoperative range of AbdER. Significant improvement of AddER, but also of AbdER and other range of motion was noted at the follow-up. The improvement of the affected shoulder function following arthroscopic plate removal was considerable and statistically significant according to the modified Constant-Murley score (p < 0,01) and SSV (p < 0.0000) after a minimum of two-year follow-up.

Conclusions

Our findings are the first to highlight the influence of deltoid muscle, plate, and humerus adhesions on limiting external rotation in adduction after ORIF treatment of proximal humerus fractures. These observations allow the identification of a new shoulder evaluation symptom: Selective Glenohumeral External Rotation Deficit (SGERD) as well as functional deltohumeral space.

Identifying the axillary nerve during shoulder surgery: an anatomic study using advanced imaging

Background

The axillary nerve (AXN) is one of the more commonly injured nerves during shoulder surgery. Prior anatomic studies of the AXN in adults were performed using cadaveric specimens with small sample sizes. Our research observes a larger cohort of magnetic resonance imaging (MRI) studies in order to gain a more representative sample of the course of the AXN and aid surgeons intraoperatively.

Methods

High-resolution 3T MRI studies performed at our institution from January 2010 to June 2019 were reviewed. Four blinded reviewers with musculoskeletal radiology or orthopedic surgery training measured the distance of the AXN to the surgical neck of the humerus (SNH), the lateral tip of the acromion (LTA), and the inferior glenoid rim (IGR). Intraclass correlation coefficient was calculated to assess reliability between reviewers. The nerve location was assessed relative to rotator cuff tear status.

Results

A total of 257 shoulder MRIs were included. Intraclass correlation coefficient was excellent at 0.80 for the SNH, 0.90 for the LTA, and 0.94 for the IGR. All intraobserver reliabilities were above 0.80. The mean distance from the AXN to SNH was 1.7 cm (range, 0.7-3.1 cm; interquartile range, 1.38-2.00) and that from the AXN to IGR was 1.6 cm (range, 0.6-2.6 cm; interquartile range, 1.33-1.88). The mean AXN to LTA distance was 7.1 cm, with a range of 5.2-9.0 cm across patient heights; there was a large effect size related to the LTA to AXN distance and patient height with a correlation of r = 0.603 (P < .001). Rotator cuff pathology appears to affect nerve location by increasing the distance between the AXN and SNH (P = .027).

Discussion/Conclusion

The AXN is vulnerable to injury during both open and arthroscopic shoulder procedures. This injury can be either a result of direct trauma to the nerve or secondary to traction placed on the nerve with reconstructive procedures that distalize the humerus. Our study demonstrates that the AXN can be found as little as 5.6 mm from the IGR and 6.9 mm from the SNH. In addition, we illustrate the relationship between patient height and the LTA to AXN distance and complete rotator cuff tears and the SNH to AXN distance. Our study is the first to demonstrate the nerve's proximity to important surgical landmarks of the shoulder using a large sample size of high-resolution images in living human shoulders.

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.

Ultrasonography-guided anterior approach for axillary nerve blockade: An anatomical study

Combined ultrasound (US)-guided blockade of the suprascapular and axillary nerves (ANs) has been proposed as an alternative to interscalene blockade for pain control in shoulder joint pathology or postsurgical care. This technique could help avoid respiratory complications and/or almost total upper limb palsy. Nowadays, the AN blockade is mostly performed using an in-plane caudal-to-cephalic approach from the posterior surface of the shoulder, reaching the nerve immediately after it exits the neurovascular quadrangular space (part of the spatium axillare). Despite precluding most respiratory complications, this approach has not made postsurgical pain relief any better than an interscalene blockade, probably because articular branches of the AN are not blocked.Cephalic-to-caudal methylene blue injections were placed in the first segment of the AN of six Thiel-embalmed cadavers using an US-guided anterior approach in order to compare the distribution with that produced by a posterior approach to the contralateral AN in the same cadaver. Another 21 formalin-fixed cadavers were bilaterally dissected to identify the articular branches of the AN.We found a good spread of the dye on the AN and a constant relationship of this nerve with the subscapularis muscle. The dye reached the musculocutaneous nerve, which also contributes to shoulder joint innervation. We describe the anatomical landmarks for an ultrasonography-guided anterior AN blockade and hypothesize that this anterior approach will provide better pain control than the posterior approach owing to complete blocking of the joint nerve. Clin. Anat. 33:488-499, 2020. © 2019 Wiley Periodicals, Inc.

Unusual anatomic variant of the axillary nerve challenging the deltopectoral approach to the shoulder: a case report

Background

The deltopectoral approach is a well-described surgical approach to the proximal humerus and glenohumeral joint. One of the structures at risk during this approach is the axillary nerve. Typically, the axillary nerve arises off the posterior cord of the brachial plexus and courses lateral to the proximal humerus and inferior to the glenohumeral joint, exiting the axilla through the quadrangular space. We describe a case of an aberrant axillary nerve, coursing anteriorly across the glenohumeral joint within the deltopectoral groove encountered during a reverse total shoulder arthroplasty.

Case presentation

A 73-year-old female presented complaining of atraumatic progressive right shoulder pain of several months duration. Clinical and radiographic findings were consistent with advanced rotator cuff arthropathy. After failing appropriate non-operative treatment, the patient elected to undergo reverse total shoulder arthroplasty. During the deltopectoral approach to the glenohumeral joint, the axillary nerve was found to be coursing deep to the cephalic vein within the deltopectoral interval. The nerve was isolated and protected, and the glenohumeral joint was accessed via a small window in the anterior deltoid muscle. The remainder of the procedure was performed without complication. The patient was found to be healing well and with normal axillary nerve function at 4-month follow-up.

Conclusions

Neurologic lesions are well-documented complications of reverse total shoulder arthroplasty. The integrity of the axillary nerve is of particular importance to reverse total shoulder arthroplasty as it innervates the deltoid and post-operative function of the extremity is dependent upon a functioning deltoid muscle. Extreme care must be taken to avoid insult to the axillary nerve and any aberrant paths it may course around the glenohumeral joint.

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.

Re-definition of position and calculation of safe area for axillary nerve in deltoid muscle with its clinical relevance: a cadaveric study

Several authors have made efforts to define the position of the axillary nerve within deltoid muscle and to calculate the so called safe area for this nerve but it still remains a matter of debate. The primary aim of the study was to investigate the acromio-axillary (AA) distance and its correlation with upper arm length. The secondary aim was to re-define the safe area for axillary nerve within deltoid muscle. Sixty shoulders of thirty adult human cadavers were dissected using standard methods. The distance from the anterior and posterior edge of acromion to the upper border of the course of the axillary nerve was measured and recorded as anterior and posterior AA distance respectively. Correlation analysis was done between the upper arm length and AA distance for each limb. The ratios between anterior and posterior AA distance and upper arm length were calculated and mentioned as anterior index and posterior index, respectively. The mean of anterior and posterior AA distance was 5.22 cm and 4.17 cm, respectively. The mean of upper arm length was 29.30 cm. The means of anterior index and posterior indices were 0.18 and 0.14, respectively. There was a significant correlation between upper arm length and both the anterior and posterior AA distance. The axillary nerve was found to lie at variable distance from the acromion. The minimum AA distance was found to be 3.50 cm. So this should be considered as the maximum permissible length of the deltoid split. Upper arm length has strong correlation with both anterior and posterior AA distances. The ideal safe area for the axillary nerve was found to be a quadrangular area above it and the size of which depends on the length of the upper arm.

Nerves Around the Shoulder: What the Radiologist Should Know?

Peripheral neuropathies of the shoulder are common and could be related to traumatic injury, shoulder surgery, infection or tumour but usually they result from an entrapment syndrome. Imaging plays an important role to detect the underlying causes, to assess the precise topography and the severity of nerve damage. The key points concerning the imaging of nerve entrapment syndrome are the knowledge of the particular topography of the injured nerve, and the morphology as well signal modifications of the corresponding muscles. Magnetic Resonance Imaging best shows these findings, although Ultrasounds and Computed Tomography sometimes allow the diagnosis of neuropathy.

Posterior shoulder instability managed by arthroscopic acromial pediculated bone-block. Technique

In posterior shoulder instability (recurrent dislocation, involuntary posterior subluxation or voluntary subluxation that has become involuntary), surgery may be considered in case of failure of functional treatment if there are no psychological contraindications. Acromial bone-block with pediculated deltoid flap, as described by Kouvalchouk, is an alternative to iliac bone-block, enabling triple shoulder locking by the blocking effect, the retention hammock provided by the deltoid flap and posterior capsule repair. Arthroscopy allows shoulder joint exploration and diagnosis of associated lesions, with opening and conservation of the posterior capsule; it greatly facilitates bone-block positioning and capsule reinsertion. The present report describes the procedure in detail.

LEVEL OF EVIDENCE

Technical note.

Is it safe to preserve the deltoid when resecting the proximal humerus for a primary malignant bone tumour? A comparative study

AIMS

Resection of the proximal humerus for the primary malignant bone tumour sometimes requires en bloc resection of the deltoid. However, there is no information in the literature which helps a surgeon decide whether to preserve the deltoid or not. The aim of this study was to determine whether retaining the deltoid at the time of resection would increase the rate of local recurrence. We also sought to identify the variables that persuade expert surgeons to choose a deltoid sparing rather than deltoid resecting procedure.

PATIENTS AND METHODS

We reviewed 45 patients who had undergone resection of a primary malignant tumour of the proximal humerus. There were 29 in the deltoid sparing group and 16 in the deltoid resecting group. Imaging studies were reviewed to assess tumour extension and soft-tissue involvement. The presence of a fat rim separating the tumour from the deltoid on MRI was particularly noted. The cumulative probability of local recurrence was calculated in a competing risk scenario.

RESULTS

There was no significant difference (adjusted p = 0.89) in the cumulative probability of local recurrence between the deltoid sparing (7%, 95% confidence interval (CI) 1 to 20) and the deltoid resecting group (26%, 95% CI 8 to 50). Patients were more likely to be selected for a deltoid sparing procedure if they presented with a small tumour (p = 0.0064) with less bone involvement (p = 0.032) and a continuous fat rim on MRI (p = 0.002) and if the axillary nerve could be identified (p = 0.037).

CONCLUSION

A deltoid sparing procedure can provide good local control after resection of the proximal humerus for a primary malignant bone tumour. A smaller tumour, the presence of a continuous fat rim and the identification of the axillary nerve on pre-operative MRI will persuade surgeons to opt for a deltoid resecting procedure. Cite this article: Bone Joint J 2017;99-B:1244-9.

Establishing a new appropriate intramuscular injection site in the deltoid muscle

It is becoming increasingly important for clinicians to identify a safer intramuscular (IM) injection site in the deltoid muscle because of possible complications following the vaccine administration of IM injections. We herein examined 4 original IM sites located on the perpendicular line through the mid-acromion to establish a safer IM injection site. Thirty healthy volunteers participated in this study and the distances from our 4 IM sites to some anatomical landmarks on their left arms were measured. Ultrasonography (US) was also performed to measure the thickness of the deltoid muscle and identify the posterior circumflex humeral artery (PCHA) along the course of the axillary nerve. Subcutaneous thickness was measured using 2 methods: measuring the skin thickness with caliper after pinching the skin, and with US. The results obtained revealed that the intersection between the anteroposterior axillary line (the line between the upper end of the anterior axillary line and the upper end of the posterior axillary line) and the perpendicular line from the mid-acromion was the most appropriate site for IM injections because it was distant from the axillary nerve, PCHA, and subdeltoid/subacromial brusa. At this site, depth of needle insertions was 5 mm greater than the subcutaneous thickness at a 90° angle, which was sufficient to penetrate subcutaneous tissue in both sexes. Subcutaneous thickness can be assessed with almost the same accuracy by US or measuring with calipers after pinching the skin. The results of the present study support the improved vaccine practice for safer IM injections.

Anatomic study and electromyographic analysis of the teres minor muscle

BACKGROUND

The teres minor muscle is a focused topic on the treatment of massive rotator cuff tears and reverse total shoulder arthroplasty. Its precise anatomy and function have not been completely investigated. The purposes of this study were to anatomically investigate the muscle and analyze electromyographic (EMG) activities during shoulder motion.

METHODS

This anatomic study used 20 shoulders from deceased donors (mean age, 75.0 years). EMG data were recorded from 10 healthy volunteers (mean age, 21.7 years) during flexion, abduction, and external rotations at 0° of abduction, at 90° of abduction, and at 90° of flexion in their dominant arms synchronized with a computerized 3-dimensional motion analysis system.

RESULTS

The muscle in all specimens consisted of 2 distinct muscular bundles: the upper and lower portions. The upper portion attached to the round area of the greater tuberosity, and the lower portion inserted into the linear shaped area. Both portions were independent in their origins, insertions, and innervation. The muscle engaged force during each shoulder motion. EMG activities of abduction and the 3 forms of external rotation were similar. Maximal voluntary contraction in the 3 forms of external rotation was 32% in maximum external rotation in the neutral position, 25% in flexion, and 40% in abduction.

CONCLUSIONS

The teres minor consists of independent upper and lower portions. The muscle engages force in all ranges of 5 shoulder motions, and maximum external rotation in abduction is a reliable method to evaluate potential activity of the muscle.

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.].

Anatomical and biomechanical evaluation of an intramedullary nail for fractures of proximal humerus fractures based on tuberosity fixation

BACKGROUND

For unstable proximal humerus fractures, both plates and nails may be recommended. We introduce an anterograde nail designed for the treatment of 3- and 4-parts proximal humerus fractures. The aim of this study is to compare the biomechanics of this nail versus a plate and then to analyze the relationships of the screws with the axillary nerve. Our working hypotheses are as follows: (1) this nail is biomechanically equal or better to the reference plate and (2) it does not endanger the axillary nerve.

METHODS

Biomechanical study: using 40 sawbones, a reproducible 4-part fracture was created and fixed first with an angle-stable plate for proximal humeral fracture, then fixed with the nail using 2 posterior screws. All specimens were mounted in a custom testing apparatus. Two trails were performed needing each time 5 "normal" and 5 "osteoporotic" bones.

ANATOMICAL STUDY

On 20 unpaired shoulders, a nail was inserted with all screws through a superior approach (deltoid split approach). Dissection of all shoulders was done to identify the axillary nerve. The distance between each screw and the axillary nerve or its branches was measured.

FINDINGS

The proximal humerus nail demonstrated higher values than locking plate for both stiffness and load to failure. The failure mode differs in function of the type of osteosynthesis. The lowest distance between a screw and the axillary nerve was 20.13 mm.

INTERPRETATIONS

We introduce a biomechanically efficient nail without increased neurological risks to improve the pullout strength of the screws to provide more secure fixation of proximal humeral fractures.

LEVEL OF EVIDENCE

Basic Science Study, Anatomic Cadaver Study.

Post operative pain management in shoulder surgery: Suprascapular and axillary nerve block by arthroscope assisted catheter placement

BACKGROUND

Postoperative pain management is the part of shoulder surgery to improve patient satisfaction, start rehabilitation process rapidly and decrease for hospital stay. Various treatment modalities have been used for pain management, but they have some limitations, side effects and risks. Throughout intraoperative and postoperative period, nerve blocks have been used more popularly than others because of efficacy. For the regional nerve block, local anesthetic should be infiltrated close to the nerve for maximum effect. Consequently, aim of this study was to evaluate analgesic efficacy when catheters are placed with assistance of arthroscope to block suprascapular and axillary nerves in patients undergoing arthroscopic repair of rotator cuff under general anesthesia.

MATERIALS AND METHODS

24 patients (5 males, 19 females; mean age: 54.3 years) who underwent arthroscopic repair of rotator cuff between June 2014 and September 2014 and were catheterized to block suprascapular and axillary nerves during shoulder arthroscopy were included in the study. Clinical outcomes were assessed using visual analog scale (VAS) scores preoperatively and at 0 h, 6 h, 12 h, 18 h, 24 h, and postoperative day 2.

RESULTS

Preoperative and postoperative 0 h, 6 h, 12 h, 18 h, 24 h, and day 2 mean VAS scores were 6.38 ± 0.77, 0.44 ± 0.42, 0.58 ± 0.42, 0.63 ± 0.40, 0.60 ± 0.44, 0.52 ± 0.42, and 1.55 ± 0.46, respectively. No statistical difference was found among 0 h, 6 h, 12 h, 18 h, and 24 h time points; however, comparison of postoperative day 2 and postoperative 0 h, 6 h, 12 h, 18h and 24 h VAS scores showed statistically significant difference (P < 0.05). All patients were discharged at the end of 24 h with no complication. The mean time (in minutes) required for blocking suprascapular nerve and axillar nerve were 14.38 ± 3.21 and 3.75 ± 0.85, respectively.

CONCLUSION

These results demonstrated that blocking two nerves with arthroscopic approach was an excellent pain management method in postoperative period. Accordingly, patients could recover rapidly and patients' satisfaction could be improved.

[New arthroscopic portal for performing tenotomy/tenodesis procedures on the long head of the biceps brachii tendon]

BACKGROUND

Shoulder arthroscopy is the standard technique for performing procedures involving the intertubercular groove. Current techniques continue to produce excessive soft tissue manipulation and neurovascular injury.

MATERIALS AND METHODS

A cross-sectional, observational and descriptive study was conducted on a cohort of 24 shoulders following the standard surgical protocol and using punch dissection. The neurovascular structures with risk of damage by the standard lateral portal were evaluated during the study to establish a secure area for a new arthroscopic portal. Finally, the safety of the new proposed site was evaluated.

RESULTS

The presence of 24 venous structures, with a mean diameter was 1.05mm (SD: 0.71) was documented. A tendency was observed in locating these structures in the lower half of the dissecting field for the left shoulders and a hypovascular area between the 7 and 10hours circle dissected relative to the right shoulder. The new site was determined at a point 1.5 cm anterolateral to the anterolateral border of the acromion at an angle of 60° degrees to the horizontal axis of the acromion and towards the intertubercular groove of the humerus.

CONCLUSIONS

The methodology used in this study is innovative, reproducible and applicable for the study of all existing shoulder arthroscopic portals procedures, as well as any joint. The results provided by this study will be helpful for clinicians to improve tenotomy/tendon tenodesis procedures of the long head of the biceps brachii tendon.

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.

Exposures of the humerus for fracture fixation

The care of humeral shaft fractures is undergoing a transition to more aggressive treatment methods with more frequent operative fixation. The upper arm has an extensive network of nerves, arteries, and veins that must be protected during any operative exposure. The ultimate goal of fixation of a humerus fracture is rigid stabilization to allow early range of motion, protection of the neurovascular structures, and preservation of the triceps mechanism posteriorly and the anterior elbow flexor muscles.

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%).

Biomechanical contributions of posterior deltoid and teres minor in the context of axillary nerve injury: a computational study

PURPOSE

To determine whether transfer to only the anterior branch of the axillary nerve will restore useful function after axillary nerve injury with persistent posterior deltoid and teres minor paralysis.

METHODS

We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 submaximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles that may compensate for their paralysis.

RESULTS

In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, whereas teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When we paralyzed posterior deltoid and teres minor, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed.

CONCLUSIONS

Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength after isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered.

CLINICAL RELEVANCE

By quantifying the biomechanical role of muscles during submaximal movement, in addition to quantifying muscle contributions to maximal shoulder strength, we can inform preoperative planning and permit more accurate predictions of functional outcomes.

Analgesic effectiveness of nerve block in shoulder arthroscopy: comparison between interscalene, suprascapular and axillary nerve blocks

PURPOSE

Postoperative pain in arthroscopic shoulder surgery cannot be easily controlled with analgesics and nerve blocks. This study shows the analgesic effect of interscalene block (ISB) and suprascapular nerve block and axillary nerve block (SSNB + ANB) in patients under patient controlled analgesia (PCA).

METHODS

Sixty-one patients (26 men and 35 women) who underwent arthroscopic rotator cuff repair were selected and allocated non-randomly to one of three groups: PCA only-group, PCA with ISB-group and PCA with SSNB + ANB-group. Visual analogue scale (VAS) score, degree of satisfaction, PCA usage and incidence of nausea and vomiting were evaluated at the recovery room, 8, 16 and 24 postoperative hours.

RESULTS

The VAS score of the PCA only-group was highest at the recovery room. The VAS score of the PCA with ISB-group was the lowest, however, with large fluctuations over time. Although the VAS score of the PCA with SSNB + ANB-group was higher than that of the PCA with ISB-group, it was steadily lower than the PCA-only group, without any fluctuations. The degree of satisfaction of the PCA with ISB-group was highest at the recovery room. The number of times the PCA was used at the 8-h postoperative evaluation was largest in the PCA only-group.

CONCLUSIONS

The initial 24 h after surgery plays a key role in controlling pain after arthroscopic shoulder surgery. PCA with SSNB + ANB is a better anaesthetic choice than PCA with ISB or PCA only during the initial 24 h of the postoperative period.

LEVEL OF EVIDENCE

Clinical study, Level II.

An anatomic and clinical study of the suprascapular and axillary nerve blocks for shoulder arthroscopy

HYPOTHESIS

The combination of suprascapular nerve block (SSNB) and axillary nerve block (ANB) has been reported to provide safe and effective analgesia for arthroscopic shoulder surgery. This study was designed to identify anatomic landmarks of the suprascapular nerve (SSN) and axillary nerve (AN) and to evaluate the effects of SSNB and ANB using the identified landmarks.

MATERIALS AND METHODS

This study included 52 cadaveric shoulders and 30 patients in the anatomic and clinical studies, respectively. After the exact location of the SSN and AN was identified from the cadavers, the clinical study at the end of the operation and at 8, 16, 24, 32, 40, and 48 hours postoperatively was performed in 2 groups: without both SSNB and ANB (group I) and with both SSNB and ANB (group II).

RESULTS

The SSN was located at a length of one-half (2/5-3/5, 88%) from the anterior tip of the acromion to the superior angle of the scapula and at a length of two-fifths (1/3-1/2, 100%) from the anterior tip of the acromion to the medial border of the spine. The AN was located at a length of three-fifths (2/5-4/5, 98%) from the acromial angle to the inferior insertion of the teres major muscle. The depth from the skin was 3.20 ± 0.58 cm for the SSN and 2.07 ± 0.45 cm for the AN. The clinical study showed that the total amount of analgesic for patient-controlled anesthesia was markedly decreased at the end of the operation and at 8 hours postoperatively in group II compared with group I.

CONCLUSIONS

The SSNB and ANB were considered to provide safe and effective analgesia in terms of early postoperative pain in arthroscopic shoulder surgery.

Ultrasound-guided block of the axillary nerve: a volunteer study of a new method

BACKGROUND

Interscalene brachial plexus block (IBPB) is the gold standard for perioperative pain management in shoulder surgery. However, a more distal technique would be desirable to avoid the side effects and potential serious complications of IBPB. Therefore, the aim of the present study was to develop and describe a new method to perform an ultrasound-guided specific axillary nerve block.

METHODS

After initial investigations, 12 healthy volunteers were included. We performed an in-line ultrasound-guided specific axillary nerve block by injecting 8 ml local anesthetic (lidocaine 20 mg/ml) after placing the tip of a nerve stimulation needle cranial to the posterior circumflex humeral artery in the neurovascular space bordered by the teres minor muscle, the deltoid muscle, the triceps muscle and the shaft of the humerus. Needle placement was aided by simultaneous nerve stimulation. We assessed sensory (pinprick and cold stimulation) and motor (active resistive force) block of the axillary nerve before, 15, 30, 60, 90 and 120 min after performing the block and every 30 min until termination of the block.

RESULTS

All 12 volunteers demonstrated sensory block of the axillary nerve and 10 volunteers demonstrated complete motor block. Even though it was difficult to directly visualize the axillary nerve, the block was easy to perform with easily recognizable ultrasonographic landmarks. Block duration was approximately 120 min.

CONCLUSIONS

We describe a new ultrasound-guided technique to specifically block the axillary nerve. The potential clinical role of this new block remains to be determined.

Anatomic study of the axillary nerve in a Chinese cadaveric population: correlation of the course of the nerve with proximal humeral fixation with intramedullary nail or external skeletal fixation

INTRODUCTION

The axillary nerve can be injured during external skeletal fixation with Schanz screws or proximal locking screws of intramedullary nails. Being aware of the axillary nerve's anatomic relationship to the proximal humerus is vital for avoiding complications.

METHODS

We investigated the relationship of the axillary nerve to surrounding bony landmarks by studying 88 axillary nerves in 44 embalmed cadaveric adult Chinese males. These measurements were then compared with the results from a similar study among Caucasians using the same reference points.

RESULTS

We identified three significantly different parameters between our Chinese and the previously studied Caucasian subjects (P ≤ 0.05): the distances from the superior aspect of the humeral head to the axillary nerve (D1) (5.2 ± 0.7 vs. 6.09 ± 0.65 cm, respectively); surgical neck to axillary nerve (D2) (2.0 ± 0.7 vs. 1.72 ± 0.84 cm); and humeral length (D3) (29.0 ± 2.2 vs. 35.25 ± 5.7 cm). The D1 distance ranged from 4.0 to 6.7 cm; the D2 distance ranged from 1.0 to 4.1 cm; and the entire humeral length (D3) ranged from 23.3 to 33.3 cm. Iatrogenic injury to the axillary nerve could be reduced by placing pins and screws in proper directions using portable C-arm fluoroscopic guidance, drill-guided protective systems, and a mini-open-incision with muscle spreading and drill protective systems directly placed on the bone.

CONCLUSION

Because of physical variability among individual patients and populations, surgeons should consider the possible courses of the axillary nerve when treating proximal humeral fractures.

Surgical anatomy of the axillary nerve and its implication in the transdeltoid approaches to the shoulder

BACKGROUND

Traumatic and iatrogenic injuries of the axillary nerve (AN) are frequent in clinical practice; nevertheless, its anatomy and its relationships with the transdeltoid approaches to the shoulder are not well documented.

MATERIALS AND METHODS

Anatomic study was performed on 16 shoulders of unembalmed cadavers. A proximal humeral internal locking system (PHILOS) plate was placed to simulate the osteosynthesis of a fracture of humeral surgical neck. The relationships between the plate and the nerve were evaluated. Selective dissection of all the nerve branches inside the deltoid muscle was performed.

RESULTS

The mean distance between the point where the AN entered into the deltoid muscle and the humeral head was 5.0 cm, and it was 6.8 cm from the acromion. The mean distance between the origins of the anterior and posterior branches of the axillary nerve was 5.4 cm. The mean diameter of the AN was 0.57 cm, the anterior branch diameter was 0.40 cm, of posterior branch diameter was 0.33 cm, and the teres minor branch diameter was 0.24 cm. The application of the PHILOS plate demonstrated that in 100% of cases, the 2 distal holes of the plate of those dedicated to the humeral head coincided with the passage of AN.

DISCUSSION

The different patterns of nerve branches inside the deltoid muscle show that the "safe zone" during transdeltoid approaches is the anterior region of the deltoid muscle for a maximum of 6.7 cm from the acromion. In addition, the insertion of the 2 distal screws of those dedicated to humeral head of the plate should be avoided.

Review of the surgical anatomy of the axillary nerve and the anatomic basis of its iatrogenic and traumatic injury

The axillary nerve is invariably reported to be one of the most commonly injured nerves during surgical procedures of the shoulder, and the importance of protecting it cannot be overemphasized. Many researchers have tried to identify safe regions, but the results vary among published studies. The axillary nerve may also be injured during acute trauma to the shoulder or by chronic repeated trauma as has been described in the quadrilateral space syndrome. The nerve injury may occur together with shoulder dislocation and rotator cuff tear, thus comprising the so-called "unhappy triad" of the shoulder joint. Simple attention to potential variations in the origin and course of the axillary nerve and its relationship to the shoulder capsule and having a precise knowledge of "safe zones" during operations can enhance clinical outcomes. The objective of this review, therefore, is to discuss the surgical anatomy of the axillary nerve and further emphasize the clinical importance of the its injury following shoulder trauma.

Surgical decompression of the quadrilateral space in overhead athletes

BACKGROUND

Quadrilateral space syndrome is an uncommon condition that can disable the overhead athlete. The authors describe 4 cases of quadrilateral space syndrome that may assist clinicians in recognition of this problem in patients with posterior shoulder pain.

HYPOTHESIS

Quadrilateral space syndrome can present as posterior shoulder pain in the overhead athlete, and surgical decompression can relieve symptoms and allow full return to activity.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between 2004 and 2006, the authors performed surgical decompression of the quadrilateral space in 4 overhead athletes (4 shoulders; mean age, 24 years). They evaluated the clinical presentations, diagnostic tests, surgical procedures, and results of treatment. Mean follow-up was 24.5 months.

RESULTS

All 4 patients underwent surgical decompression of the quadrilateral space. Fibrous bands entrapped the axillary nerve in 3 shoulders, and venous dilation was found in the fourth shoulder. All patients returned to full activity without pain or limitation of overhead function 12 weeks after surgery.

CONCLUSION

Quadrilateral space syndrome is an uncommon cause of posterior shoulder pain that is easily overlooked and can severely limit overhead function in the athlete. Surgical decompression can predictably relieve pain and improve function in patients who do not respond to nonoperative regimens.

Arthroscopic perspective of the axillary nerve in relation to the glenoid and arm position: a cadaveric study

PURPOSE

The purposes of this study were to examine the morphologic features of the axillary nerve and its relation to the glenoid under an arthroscopic setup, and to determine the changes in nerve position according to different arm positions.

METHODS

Twenty-three fresh-frozen fore-quarter cadaveric shoulder specimens were used for evaluations in an arthroscopic setup with the lateral decubitus position. The main trunk of the axillary nerve with or without some of its branches was exposed after careful arthroscopic dissection. Morphologic features and the course of the axillary nerve from the anterior and posterior portals were documented. The closest distances from the glenoid rim were measured with a probe by use of a distance range system. The changes in nerve position were determined in 4 different arm positions. At the end of arthroscopic examination, the nerves were marked and verified by open dissections.

RESULTS

The axillary nerve appeared in the joint near the inferior edge of the subscapularis muscle. With reference to the inferior glenoid rim horizontally, the nerve had a mean running angle of 23 degrees (range, 14 degrees to 41 degrees; SD, 8 degrees ). The closest points from the glenoid were between the 5:30- and 6:00-o'clock position (right) or 6:00- and 6:30-o'clock position (left). The closest distance range varied from 10 to 25 mm in the neutral arm position. The abduction-neutral position resulted in the greatest distance between the inferior glenoid and the nerve.

CONCLUSIONS

The abduction-neutral rotation position was the optimal position for minimizing axillary nerve injuries, because it resulted in the greatest distance between the inferior glenoid and the nerve.

CLINICAL RELEVANCE

Knowledge of the anatomy of the axillary nerve aids the shoulder surgeon in avoiding nerve injury during arthroscopic procedures. Abduction-neutral rotation may be more helpful for arthroscopic surgeons performing procedures in the anteroinferior glenoid with the nerve being farther away from the working field.