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

Axillary nerve: what anesthesiologists and pain physicians should know

Innervation of the shoulder joint is complex and remains poorly understood among regional anesthesiologists and chronic pain specialists. Current literature supports the important contribution of the axillary nerve to the total innervation of the shoulder, as well as its blockade for perioperative pain and denervation for chronic shoulder pain. However, a description of the entire course of the axillary nerve, the corresponding optimal targets, and the sonoanatomy pertinent to pain intervention is lacking. This educational article discusses in detail the functional anatomy and sonographic identification of possible windows for axillary nerve intervention. We discuss the contribution, extent, and type of innervation the axillary nerve provides to the shoulder joint, which is often misunderstood. Ultimately, this article serves to stimulate thoughts and ideas for future research in an area where literature is scarce.

Comparison of classical and minimally invasive superolateral approach for reconstruction of proximal humerus fractures with locking plates

CONTEXT

Minimally invasive (MI) approaches are purported to present advantages for osteosynthesis when compared with conventional approaches. This study aimed to compare the medium-term clinical and radiological outcomes of patients with proximal humerus fractures treated by plate osteosynthesis with conventional and MI superolateral approaches.

METHOD

The study carried out was a retrospective monocentric comparative analysis. Forty-three cases were followed up - 18 were treated with an MI approach and 25 with a conventional approach. Constant-Murley, DASH and SSV scores were established and standard complications were investigated.

RESULTS

No significant differences in functional scores or complications were found between the 2 groups. The only significant difference was for pain which was significantly lower for the MI group. The overall revision rate was 18.3 %. The mean adjusted Constant-Murley for the entire population was 80.1 ± 20.2; the mean DASH score was 17.8 ± 15.9 and the mean SSV was 73.2 ± 19.5.

CONCLUSION

This study did not demonstrate any significant differences between the 2 approaches. Given the low patient population in our series, the superiority of the MI approach - as indicated in the literature - was not proven.

Neuropathy of the suprascapular and axillary nerves in rotator cuff arthropathy: a prospective electrodiagnostic study

PURPOSE

Prevalence of axillary (AN) and/or suprascapular (SSN) neuropathy in rotator cuff tear arthropathy (RCTA) is unknown. We aimed to prospectively evaluate for preoperative neurodiagnostic abnormalities in order to determine their prevalence, location, and influence on reverse shoulder arthroplasty (RSA) outcomes.

METHODS

Patients who underwent RSA for RCTA were prospectively included. An electromyography and nerve conduction study were performed pre and post-surgery. Clinical situation: VAS, Relative Constant-Murley Score (rCMS) and ROM over a minimum of two years follow-up.

RESULTS

Forty patients met the inclusion criteria; mean follow-up was 28.4 months (SD 4.4). Injuries in RCTA were present in 83.9% (77.4% in AN and 45.2% in SSN). There were no differences on preoperative VAS, ROM, and rCMS between patients with and without preoperative nerve injuries. Four acute postoperative neurological injuries were registered under chronic preoperative injuries. Six months after RSA, 69% of preoperative neuropathies had improved (82.14% chronic injuries and 77.7% disuse injuries). No differences in improvement between disuse and chronic injuries were found, but patients with preoperative neuropathy that had not improved at the postoperative electromyographic study at six months, scored worse on the VAS (1.44 vs 2.66; p .14) and rCMS (91.6 vs 89.04; p .27).

CONCLUSIONS

The frequency of axillary and suprascapular neuropathies in RCTA is much higher than expected. Most of these injuries improve after surgery, with almost complete neurophysiological recovery and little functional impact on RSA. However, those patients with preoperative neuropathies and absence of neurophysiological improvement six months after surgery have lower functional results.

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.

High-Resolution Ultrasound Imaging of Axillary Nerve and Relevant Injury

OBJECTIVE

To evaluate the feasibility of axillary nerve (AN) visualization in healthy volunteers and the diagnostic value of AN injury via high-resolution ultrasonography (HRUS).

METHODS

AN was examined by HRUS on both sides of 48 healthy volunteers and oriented the transducer according to three anatomical landmarks: quadrilateral space, anterior to subscapular muscle, and posterior to axillary artery. The maximum short-axis diameter (SD) and cross-sectional area (CSA) of AN were measured at different levels, and AN visibility was graded by using a five-point scale. The patients suspected of having AN injury were assessed by HRUS, and the HRUS features of AN injury were observed.

RESULTS

AN can be visualized on both sides in all volunteers. There was no significant difference in SD and CSA of AN at the three levels between the left and right sides or in SD between males and females. However, the CSA of males at different levels was slightly larger than those of females (P < .05). In most volunteers, AN visibility at different levels was excellent or good, and AN was best displayed anterior to subscapular muscle. Rank correlation analysis revealed that the degree of AN visibility had correlation with height, weight, and BMI. A total of 15 patients diagnosed with AN injury, 12 patients showed diffuse swelling or focal thickening in AN, and 3 patients showed AN discontinuity.

CONCLUSION

HRUS is able to reliably visualize AN, and it could be considered as the first choice for diagnosing AN injury.

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.

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.

Elongation of the brachial plexus after reverse shoulder arthroplasty: an anatomical study

INTRODUCTION

The use of reverse shoulder arthroplasty (RSA) is becoming more extended and its clinical results are good or excellent according to the literature. The main biomechanical characteristic of RSA is that it lowers and medializes the centre of rotation of the shoulder causing an arm lengthening. Although the number of neurological complications is low (5%), there are more neurophysiological changes in the brachial plexus with RSA than with the anatomic shoulder arthroplasty. The main goal of this study was to quantify the lengthening of the terminal branches of the brachial plexus suffered after RSA implantation.

MATERIALS AND METHODS

20 Embalmed cadavers were analysed. Four distances using bone references were employed to measure the lengthening of the arm and subacromial space. The brachial plexus and its terminal branches (radial, axillary, ulnar, musculocutaneous and median nerves) and the axillary artery, were identified and marked. Measurements were made to determine the change of position of the neurovascular structures, the arm lengthening and the lengthening of each nerve before and after the implantation of RSA. Two models of RSA were used: SMR^®(Lima) and Delta Xtend^®(DePuy-Synthes).

RESULTS

The mean arm elongation was 10.5 mm. The subacromial space suffers an elongation of 20.5-29.8%. All the neurovascular structures suffered elongation: median nerve 23.1%, musculocutaneous nerve 22.1%, ulnar nerve 19%, radial nerve 17%, axillary nerve 12-14.5%, axillary artery 24.8%. There were no differences in the results between the types of prosthesis.

CONCLUSIONS

Due to its design, the RSA causes an arm lengthening which is reflected by the elongation of the neurovascular structures of the arm.

Deltoid Intramuscular Injections: A Systematic Review of Underlying Neurovascular Structures to the Muscle and Proposing a Relatively Safer Site

The deltoid is the preferred site for intramuscular injection (IMI) because of its easy accessibility for drug and vaccine administration. Government immunization advisories, standard anatomy textbooks, and researchers have proposed various injection techniques and sites, but specific guidelines are lacking for the administration of IMIs in the increasingly used deltoid site. This study analyzes the procedures of administering IMIs in the deltoid related to the neurovascular network underlying the muscle and proposes a preferred site with the least chance of injury. The review protocol was submitted with PROSPERO (ID: 319251). PubMed, Google Scholar, and Websites of National Public Health Agencies were searched from 1950 up to 2022 for articles, advisories, and National Immunization Guidelines using Medical Subject Headings (MeSH) terms, including IMIs, deltoid muscle, safe injection sites, to identify recommendations for safer sites and techniques of administering deltoid IMIs. All the authors strictly adhered to a well-developed registered review protocol throughout the study and followed the risk of bias in systematic reviews (ROBIS) guidance tool. The proposed sites and landmark data were tabulated, and each site was analyzed based on the underlying neurovascular structures. Data were depicted by self-generated images. The initial search identified 174 articles. After applying the inclusion and exclusion criteria, 57 articles were shortlisted. Out of the 39 selected articles, 18 focused on the administration of deltoid IMIs, whereas seven focused on the variations in the underlying neurovascular structures in proximity to the deltoid muscle. The remaining 14 articles were the immunization guides issued by the National Public Health Agencies of the Government of India and abroad, whose data was used for comparison. Twelve deltoid IMI sites and techniques were identified. A site 1-3 fingerbreadths/5 cm below the mid-acromion point (7 studies); mid-deltoid site/densest part of the deltoid (1 study); a site at the middle third of the deltoid muscle (1 study); triangular injection site (1 study). Limitations included the unavailability of free access to complete text in many articles resulting in exclusion. The area around the shoulder joint and up to the lower level of the intertubercular sulcus is highly vascularized by the presence of many anomalous arterial patterns. To avoid injury, a safer site is proposed of 5 fingerbreadths/10 cm below the midpoint of the lateral border of the acromion. The authors received no specific funding for this study except for the journal publication charges.

Arthroscopically Assisted Humeral Head Decompression for Avascular Necrosis: Lateral Cortical Perforation Technique

Avascular necrosis (AVN) of the humeral head is debilitating condition that, when left untreated, can progress to humeral head collapse and end-stage arthritis of the glenohumeral joint. Core decompression is widely regarded as a first-line surgical treatment for early-stage AVN, and when performed on the appropriate patient, core decompression is an effective treatment for improving symptoms and preventing progression and humeral head collapse. This article discusses operative indications and presents a relatively simple and effective arthroscopic method for core decompression of humeral head avascular necrosis.

Functional deficits as a result of brachial plexus injury in anterior shoulder dislocation

The incidence of brachial plexus injuries in anterior shoulder dislocation remains relatively uncommon. A retrospective study was conducted to observe the natural neurological recovery of patients following these injuries over a 2-year period. Muscle power according to the Medical Research Council scale and sensation were measured from presentation to discharge. In 28 patients, the power grade of proximal muscles supplied by nine injured nerves failed to improve over a median follow-up of 5 months. There was no statistically significant improvement in sensation over a median follow-up of 6 months. Poorer recovery in muscle power score was related to advancing age, whereby every decade increased the risk by approximately 30%. Anterior shoulder dislocation with a plexus injury carries a risk of permanent nerve injury. Patients should be referred for specialist nerve assessment leading to rehabilitation and timely early nerve reconstruction, if indicated.Level of evidence: IV.

Structures Endangered During Minimally Invasive Plate Osteosynthesis of the Upper Extremity

Minimally invasive plate osteosynthesis is a surgical technique that is becoming increasingly common because radiographic images and implant technologies advance in capabilities. It is imperative for surgeons to enhance their understanding of the surgical anatomy related to new approaches for fracture fixation. While performing minimally invasive plate osteosynthesis, there is a danger of injuring structures in the common percutaneous and submuscular pathways. We describe the critical anatomical structures in these pathways and tips for injury avoidance when operating on the clavicle, scapula, humerus, and wrist.

Quadrilateral space syndrome induced by a large degenerative osteophyte

A 41-year-old gentleman presented with decreased range of motion. Initial radiographs demonstrated extensive osteoarthritic changes involving the glenohumeral joint with a large inferior oriented osteophyte. Subsequent MRI of the shoulder was obtained which demonstrated isolated fatty atrophy of the teres minor and, to a lesser extent, deltoid muscles. The axillary nerve was visualized entering the quadrilateral space which, although, was severely narrowed secondary to the large osteophyte. The patient's clinical symptoms and MRI findings were consistent with quadrilateral space syndrome. The patient wanted to attempt conservative therapy first; and therefore, subsequently underwent physical therapy with improvement of shoulder strength and range of motion.

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.

Complications after open Latarjet procedure: influence of arm positioning on musculocutaneous and axillary nerve function

BACKGROUND

Alterations in the anatomical relationships of the musculocutaneous (MCN) and axillary nerves and the influence of arm positioning on these relationships after a Latarjet procedure have been demonstrated in the cadaver, but there are no studies in the literature that establish if there is any neurophysiological repercussion.

METHODS

We retrospectively identified 24 patients with a primary or revision open Latarjet procedure. A prospective clinical (Constant-Murley, Rowe and Walch-Duplay and active range of motion), radiographic (with CT), and electrodiagnostic evaluation was made at the most recent follow-up.

RESULTS

Nonunion occurred in four patients (22%); there were, as well, one case of partial coracoid reabsorption (5%) and two (11%) with mild glenohumeral osteoarthritis. In the anatomical position, we found no alterations in the musculocutaneous nerve and two cases (11%) in the axillary nerve slight motor unit loss. In the risk position, 11 cases (61%) had neurophysiological involvement (36% had neurophysiological changes in the musculocutaneous nerve and 64% in the axillary nerve). No differences between patients with or without neurophysiologic changes were found: Constant 87/83; Rowe 89/90; Walch-Duplay 84/78; Forward elevation 175º/170º, abduction 165°/175°; external rotation 48°/45°.

CONCLUSION

The rate of clinical electromyographic changes in the axillary and MCN in the abducted and externally rotated arm position (risk dislocation position) is higher than in neutral position. Nonunion of the coracoid process must play a role in these neurophysiological changes. Although in the medium-term they don't have clinical impact, further randomized prospective studies with a larger sample size are necessary to determine their true repercussion.

LEVEL OF EVIDENCE

Level IV.

Feasibility of arthroscopic decompression of the axillary nerve in the quadrilateral space: Cadaver study

INTRODUCTION

Axillary nerve compression is a rare, but disabling condition. The three main causes are quadrilateral space syndrome among young athletes, compression due to an inferior glenohumeral osteophyte in early osteoarthritis and isolated teres minor atrophy secondary to triceps hypertrophy. The diagnosis is clinical, but may be reinforced by an electromyogram or corticosteroid injection. The usual surgical treatment is open nerve decompression using a posterior approach. Arthroscopy is a less invasive approach that should be useful in theory.

HYPOTHESIS

Arthroscopic decompression of the axillary nerve is safe and less invasive than open techniques.

MATERIAL AND METHODS

Arthroscopic nerve decompression was performed as described by PJ Millet and TR Gaskill on 10 shoulders from 6 frozen cadavers. An open posterior approach was then made to verify the effectiveness of the nerve decompression.

RESULTS

The axillary nerve and its branches, the circumflex artery and the triceps were always sufficiently released in the space below the joint capsule. When the joints were subsequently opened by a posterior approach, complete nerve decompression was confirmed in all cases with no iatrogenic lesions.

DISCUSSION

The good results of this study are encouraging, but should be supplemented with a comparative study in patients of open versus arthroscopic axillary nerve release.

CONCLUSION

We think this arthroscopic technique is a good option for treating axillary nerve compressions. The complication risk is expected to be low.

LEVEL OF EVIDENCE

IV.

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.

Neurotization of isolated axillary nerve palsy in a teenage patient

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Isolated axillary nerve palsy is a very rare condition, resulting most often from shoulder dislocation, motor vehicle accidents or iatrogenic injury.

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Loss of shoulder sensibility and abduction are the mean symptoms. And Electromyography (EMG) test helps to confirm the diagnoses.

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Long head triceps branch transfer to the axillary nerve is a good surgical procedure.

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Favorable results are associated with young age, early intervention time and adequate rehabilitation.

Background and aim

The aim of this article was to study isolated axillary nerve injury, his etiologies, symptomatology and treatment via nerve transfer or neurotization.

Methods

We describe the procedure of long head triceps radial branch transfer to the axillary nerve motor branch in adolescent patient with right deltoid muscle palsy and shoulder anesthesia following a motorcycle crush six months ago.

Results

Total recovery of the shoulder sensibility, abduction and extension at one-year follow-up, and patient returned progressively to his normal live and sports activities without any functional effect on the donor muscle.

Conclusion

The advantages of the axillary nerve transfer are demonstrated through many publications. It is a good therapeutic option if it concerned a young patient and practiced at early time followed by adequate rehabilitation.

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.

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.

How close is the axillary nerve to the inferior glenoid? A magnetic resonance study of normal and arthritic shoulders

INTRODUCTION

Axillary nerve injury is a major complication of shoulder surgery during glenoid exposure. The aim of this study was to measure the mean distance between the inferior glenoid and the axillary nerve in healthy shoulders and then to compare this distance between osteoarthritic and rotator cuff deficient glenohumeral joints.

METHODS

The magnetic resonance images of 50 patients with normal glenohumeral joints were reviewed. The infra-glenoid tubercle was determined as a fixed point and the distance to the axillary nerve was measured. Two separate assessors measured on the same sagittal sections. With a study power of 80%, the sample needed in each comparison group was 28 patients. Measurements were then performed on scans in patients with osteoarthritis and cuff tear arthropathy. The mean distance was compared between groups.

RESULTS

The mean distance between the infra-glenoid tubercle and axillary nerve was 12mm (standard deviation, SD, 5.6mm) in normal shoulders, 10.6mm (SD 5.4mm) in shoulders with osteoarthritis and 9.7mm (SD 3.7mm) in those with cuff tear arthropathy. For this sample size of 50 patients with a confidence interval of 95%, the mean range is 12mm (95% CI 10.4-13.6). A comparison between normal shoulder and osteoarthritis showed a p-value of 0.3, and between normal and cuff tear arthropathy a p-value of 0.06. This was not statistically significant.

CONCLUSIONS

The axillary nerve lies on average 12mm from the infra-glenoid tubercle. The presence of inferior osteophytes in glenohumeral osteoarthritis and the proximal migration of humeral head in cuff tear arthropathy does not seem to alter the course of the nerve significantly in relation to the inferior glenoid tubercle.

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.

Incidence, diagnostics and treatment algorithm of nerve lesions after traumatic shoulder dislocations: a retrospective multicenter study

BACKGROUND

The shoulder is the joint most prone to dislocating in the human body and accounts for 45% of all dislocations. In addition to ruptures of the soft tissue and bony injuries, lesions to vascular structures as well as the brachial plexus and its corresponding nerves might occur. With an incidence of up to 65%, nerve lesions are frequently reported after shoulder dislocations. The aim of this study is to obtain information on epidemiology, diagnostics, treatment and duration until remission or late sequelae after shoulder dislocation and concomitant nerve injury in a large patient cohort.

METHODS

The patient cohort consisted of 15,739 patients from three centres who had sustained a shoulder dislocation. All patient files were searched for concomitant injury of the brachial plexus or its corresponding nerves. For epidemiological data analysis, demographic data, clinical follow-ups, electromyography and nerve conduction velocity were evaluated.

RESULTS

In total, 60 patients (32 males, 28 females) with a mean age of 60 years (range 19-88 years) met the inclusion criteria. In the majority of patients (n = 51), the trauma mechanism was a trivial fall on the outstretched arm. The most frequent dislocation direction was anterior-caudal in 61.6%, followed by strictly caudal in 16.6%. The brachial plexus was injured in 46 patients (76.6%) and isolated nerve damage was documented in 14 patients (23.3%). Electroneurographic examinations were performed in less than half of the patients (38.3%).

CONCLUSION

A combination injury of shoulder dislocation and plexus lesion may occur at any age and sometimes has a poor outcome. Electroneurographic examinations should be implemented when managing these patients as a cost-effective and supportive examination.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Exploration of the axillary nerve through an open posterior endoscopic-assisted (OPEA) approach: First clinical experience

INTRODUCTION

Previous studies have described a segment of the axillary nerve (AN) that cannot be surgically explored through the deltopectoral and posterior surgical open approaches (blind zone). We present the first two cases using an endoscopic-assisted approach to explore the AN through a posterior approach.

MATERIAL AND METHODS

Two patients were evaluated, in whom clinical, electrodiagnostic testing, and MRI could not localize the level of the AN dysfunction. An open posterior endoscopic-assisted (OPEA) approach was performed 4 and 9 months after injury in an attempt to visualize all segments of the AN. Photographs and videos were taken to evaluate the intraoperative visualization of the AN and provide long-term clinical follow-up.

RESULTS

Almost the entire AN was visualized with the scope through the OPEA approach, avoiding the deltopectoral approach. No AN lesion was found during the nerve exploration. A triceps branch to AN transfer, using the previous posterior approach, was performed. Patients in both groups achieved a deltoid muscle function of BMRC grade 4 after 24 and 9 months, respectively.

CONCLUSION

The exploration of the AN through the OPEA approach was a useful strategy to visualize the blind zone of the AN without requiring the addition of a deltopectoral approach. We believe this novel technique has a role in selected cases of AN injury.

ANTEROLATERAL APPROACHES FOR PROXIMAL HUMERAL OSTEOSYNTHESIS: A SYSTEMATIC REVIEW

Objective:

Anterolateral approaches for proximal humerus osteosynthesis have great advantages because they allow direct exposure of the lateral aspect of the humerus without the muscular retraction seen in the deltopectoral approach. However, much resistance is found among surgeons due to the potential risk of iatrogenic injury to the axillary nerve. To identify the incidence of axillary nerve iatrogenic lesions and evaluate the functional results of proximal humerus osteosynthesis with locking plates using anterolateral approaches.

Methods:

The literature review followed the PRISMA protocol.

Results:

A total of 23 articles were selected from 786 patients submitted to anterolateral approaches. Three cases (0.38%) of iatrogenic axillary nerve lesions were confirmed. The results of the functional tests were similar to those of the deltopectoral approach.

Conclusion:

Anterolateral approaches are a viable and safe alternative for proximal humerus osteosynthesis with locking plate. Subacromial impingement was the most frequent complication. Level of Evidence II, Systematic Review.

Risk of neurological injury in posterior bone block surgery for recurrent glenohumeral instability: a cadaveric study

INTRODUCTION

Recurrent posterior glenohumeral instability poses a challenge for treatment. Bone block procedures have been advocated in cases where a bony defect is present. However, these techniques are not free of complications due to the proximity of neurovascular structures. The aim of this study is to measure the distance to the axillary and suprascapular nerves at the different steps of the procedure.

MATERIALS AND METHODS

Ten frozen human cadavers were used. The bone graft was prepared and placed on the posterior aspect of the glenoid, where it was fixed with two K-wires in different positions: parallel to the articular surface and with 20° of medial angulation. The distance from the entry and exit points of the K-wires to the axillary and suprascapular nerves was measured.

RESULTS

At the exit point, mean distance from the superior K-wire to the axillary nerve was 4.4 mm in the neutral position and 14.4 mm when medially angulated (p = 0.01) and 2.6 mm and 11.5 mm, respectively, for the inferior K-wire (p < 0.01). No differences were found at the entry point (p = 0.7 and p = 0.3). For the suprascapular nerve, mean distance to the entry point of the superior K-wire was significantly greater when it was inserted with 20° of medial angulation than when placed in neutral position (p = 0.04). No differences were found for the inferior K-wire (p = 0.35).

CONCLUSION

Posterior bone block surgery should be performed taking into consideration the possibility of axillary nerve injury anteriorly at the exit point of the K-wires. Wire and screw insertion parallel to the glenoid articular surface may reduce the risk, while increased wire or screw medial angulation with respect to the glenoid surface may heighten risk.

LEVEL OF EVIDENCE

Not applicable (cadaveric study).

The change in position of the axillary nerve with rotation of the arm

The axillary nerve is the most commonly injured nerve around the arm. In the deltopectoral approach, classical teaching states that lateral rotation of the humerus increases the distance between the subscapularis and the axillary nerve. This is the first anatomical study to quantify the distance change between the axillary nerve and subscapularis produced by arm rotation. Eight arms were placed in the supine position and a classical deltopectoral approach was performed. With digital calipers, measurements were made from the closest identifiable margin of the nerve to the inferior extent of the tenotomy. All measurements were made with the arm in 0° abduction and elbow in 90° of flexion, and repeated with the arm in 45° of medial rotation, 0° lateral rotation and 45° of lateral rotation. The mean d Axillary Nerve to subscapularis was recorded as 30.9 mm (95% CI:25.3-36.3), 39.4 mm(95% CI:34.1-44.8), and 46.1 mm (95% CI:41.1-51.2) for 45° MR, 0°, and 45° LR, respectively. Using paired-samples T-testing, the mean change in distance when moving from 45° MR to 0° was +8.5 mm (P < 0.0001), and from 0° to LR 45°, +6.7 mm (P < 0.0001). There is a significant difference in the distance between the subscapularis tenotomy and the axillary nerve with medial and lateral rotation. Laterally rotating the arm increased the distance by 6.7 mm, reaffirming that positioning the glenohumeral joint in a position of LR during subscapular tenotomy is protective against iatrogenic injury of the axillary nerve. Clin. Anat. 32:268-271, 2019. © 2018 Wiley Periodicals, Inc.

Axillary Sonography of the Shoulder: An Adjunctive Approach

Sonography of the shoulder is widely used to assess various disorders, including tendinous diseases of the rotator cuff and the long head of the biceps brachii muscle. The shoulder is commonly explored through anterior, superior, and posterior approaches, but the inferior axillary approach is rarely considered in the literature. However, this technique allows the direct visualization of relevant anatomic structures. The aim of this pictorial essay is, first, to technically describe this approach and the normal musculoskeletal sonographic anatomy of the region and, second, to present the sonographic findings of shoulder disorders that may be helpfully explored this technique.

Risk of Axillary Nerve Injury in Standard Anterolateral Approach of Shoulder: Cadaveric Study

Introduction: The anterolateral acromion approach of the shoulder is popular for minimally invasive plate osteosynthesis (MIPO) technique. However, there are literatures describing the specific risks of injury of the axillary nerve using this approach. Nevertheless, most of the studies were done with Caucasian cadavers. So, the purpose of this study was to evaluate the risk of iatrogenic axillary nerve injury from using the anterolateral shoulder approach and further investigate the location of the axillary nerve, associated with its location and arm length in the Asian population that have shorter arm length compared to the Caucasian population.

Materials and Methods: Seventy-nine shoulders in fourty-two embalmed cadavers were evaluated. The bony landmarks were drawn, and a vertical straight incision was made 5cm from tip of the acromion (anterolateral approach), to the bone. The iatrogenic nerve injury status and the distance between the anterolateral edge of the acromion to the axillary nerve was measured and recorded.

Results: In ten of the seventy-nine shoulders, the axillary nerve were iatrogenically injured. The average anterior distance was 6.4cm and the average arm length was 30.2cm. The anterior distance and arm length ratio was 0.2.

Conclusion: Our results demonstrated that the recommended safe zone at 5cm from tip of acromion was not suitable with Asian population due to shorter arm length, compared to Caucasian population. The location of axillary nerve could be predicted by 20% of the total arm-length.

Injury to the axillary and suprascapular nerves in rotator cuff arthropathy and after reverse shoulder arthroplasty: a prospective electromyographic analysis

BACKGROUND

Neurologic pre- and postoperative injuries to the axillary and/or suprascapular nerve (SSN) have a higher incidence than expected and may lead to significantly decreased functional outcomes and increased risk of reverse shoulder arthroplasty (RSA) failure.

METHODS

Patients who underwent a RSA for rotator cuff tear arthropathy (RCTA) were included from December 2014 to December 2015. This study focused on the clinical (Constant score), radiographic, and pre- and postoperative electromyographic evaluations at 3 and 6 months.

RESULTS

Twenty patients met the inclusion criteria. One was lost to follow-up. Preoperatively, 15 patients showed changes on electromyography (9 SSN and 15 axillary nerve lesions); all of them were chronic and disuse injuries. The mean preoperative relative Constant score (rCS) of all included patients was 39 ± 9 (range, 19-64). At 3 months postsurgery, the prevalence of acute injuries for both nerves was 31.5%. At 6 months postsurgery, 2 axillary nerve injuries and 6 SSN injuries remain unchanged, and the rest improved or normalized. The mean postsurgery rCS of the entire cohort at 6-month follow-up was 78 ± 6.5. Mean postoperative rCS for acute postoperative nerve injury was 71 ± 3 for the axillary nerve and 64 ± 5 for SSN.

CONCLUSIONS

Axillary and SSN injuries in RCTA have a much higher incidence than expected. Most of these axillary lesions are transient, with an almost complete recovery seen on electromyography at 6 months and with scarce functional impact. However, SSN lesions appear to behave differently, with poor functional results and having a lower potential for a complete recovery.

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.

A modified deltoid splitting approach with axillary nerve bundle mobilization for proximal humeral fracture fixation

INTRODUCTION

The deltopectoral and the deltoid splitting approach are commonly used for the treatment of proximal humeral fractures. While the deltopectoral approach requires massive soft tissue devascularization, the deltoid splitting approach needs an additional skipped incision to avoid axillary nerve injury. The purpose of this study was to describe a modified anterolateral deltoid splitting approach with axillary nerve bundle mobilization in the treatment of proximal humeral fractures and to assess its radiologic and clinical outcomes.

PATIENTS AND METHODS

Twenty-two consecutive patients with proximal humeral fractures were treated with minimally invasive plate osteosynthesis by using a modified anterolateral deltoid splitting approach with axillary nerve bundle mobilization. The patients were divided into two groups: 10 patients of Neer type 2 or 3 fractures vs. 12 patients of Neer type 4 fractures. The mean age of the study population was 63.5 years (range: 30-80 years). Six patients had valgus impacted fractures, and nine had fractures with medial comminution.

RESULTS

Fracture union was achieved in all cases. The mean time to union was 8.6 weeks (range: 6-12 weeks). Major complications, such as avascular necrosis of the humeral head and varus collapse at the fracture site, were not observed. No patients had clinically detectable sensory deficits in the axillary nerve distribution or paralysis of the anterior deltoid muscle. The mean neck-shaft angle at the final follow-up was 136.9° (range, 115°-159°). The mean visual analog score for patient satisfaction was 9.1 (range, 6-10), and the mean Neer scores were 93.5 (range, 84-100). There were no significant differences between the two groups with respect to radiologic and clinical outcomes except Neer scores: 95.8 (range: 86-100) in Neer type 2 or 3 fractures and 91.7 (range: 84-99) in Neer type 4 fractures.

CONCLUSION

The use of a modified anterolateral deltoid splitting approach with axillary nerve bundle mobilization in the treatment of proximal humeral fractures yielded excellent outcomes. This approach is a useful alternative to the deltopectoral or the deltoid splitting approaches in the treatment of proximal humeral fractures.

Change in the Distance From the Axillary Nerve to the Glenohumeral Joint With Shoulder External Rotation or Abduction Position

BACKGROUND

This study investigated whether axillary nerve (AN) distance to the inferior border of the humeral head and inferior glenoid would change while placing the glenohumeral joint in different degrees of external rotation and abduction.

METHODS

A standard deltopectoral approach was performed on 10 fresh-frozen cadaveric specimens. The distance between AN and the inferior border of the humeral head and inferior glenoid while placing the shoulder in 0°, 45°, and 90° of external rotation or abduction was measured. Continuous variables for changes in AN position were compared with paired 2-tailed Student t test.

RESULTS

The mean distance between the AN and the humeral head with the shoulder in 0°, 45°, and 90° of external rotation and 0° of abduction was 13.77 mm (SD 4.31), 13.99 mm (SD 4.12), and 16.28 mm (SD 5.40), respectively. The mean distance between the AN and glenoid with the shoulder in 0°, 45°, and 90° of external rotation was 16.33 mm (SD 3.60), 15.60 mm (SD 4.19), and 16.43 (SD 5.35), respectively. The mean distance between the AN and the humeral head with the shoulder in 0°, 45°, and 90° of abduction and 0° of external rotation was 13.76 mm (SD 4.31), 10.68 mm (SD 4.19), and 3.81 mm (SD 3.08), respectively. The mean distance between the AN and glenoid with the shoulder in 0°, 45°, and 90° of abduction was 16.33 mm (SD 3.60), 17.66 mm (SD 5.80), and 12.44 mm (SD 5.57), respectively.

CONCLUSIONS

The AN position relative to the inferior aspect of the glenohumeral joint does not significantly change despite position of external rotation. Increasing shoulder abduction over 45° decreases the distance from the glenohumeral joint to the AN and should be avoided.

Results of Operative Treatment of Brachial Plexus Injury Resulting from Shoulder Dislocation: A Study with A Long-Term Follow-Up

BACKGROUND

Injury to the infraclavicular brachial plexus is an uncommon but serious complication of shoulder dislocation. This work aims to determine the effectiveness of operative treatment in patients with this type of injury.

METHODS

Thirty-three patients (26 men and 7 women; mean age, 45 years and 3 months) treated operatively for brachial plexus injury resulting from shoulder dislocation between the years 2000 and 2013 were included in this retrospective case series. Motor function of affected limbs was assessed pre- and postoperatively with the use of the British Medical Research Council (BMRC) scale. Sensory function in the areas innervated by ulnar and median nerves was evaluated with the BMRC scale modified by Omer and Dellon and in the remaining areas with the Highet classification. Follow-up lasted 2-10 years (mean, 5.1 years).

RESULTS

Good postoperative recovery of nerve function was observed in 100% of musculocutaneous, 93.3% of radial, 66.7% of median, 64% of axillary, and 50% of ulnar nerve injuries. No recovery was observed in 5.6% of median, 6.7% of radial, 10% of ulnar, and 20% of axillary nerve injuries. Injury to a single nerve was associated with worse treatment outcome than multiple nerve injury.

CONCLUSIONS

Obtaining improvement in peripheral nerve function after injury resulting from shoulder dislocation may require operative intervention. The type of surgical procedure depends on intraoperative findings: sural nerve grafting in cases of neural elements' disruption, internal neurolysis when intraneural fibrosis is observed, and external neurolysis in the remaining cases. The outcomes of surgical treatment are good, and the risk of intra- and postoperative complications is low.

Arthroscopic-assisted exploration of the axillary nerve through a posterior open approach: A novel technique

INTRODUCTION

Previous studies have described a segment of the axillary nerve (AN) that cannot be surgically explored through standard open surgical approaches (blind zone). This study aimed to evaluate the feasibility of combining the standard posterior approach to the AN by using an arthroscope to visualize all segments of the AN.

MATERIAL AND METHODS

Four fresh-frozen shoulders in two adult human torsos were included in the study. A standard posterior approach was performed on each shoulder, and a dry arthroscopy was performed through the surgical opening in an attempt to visualize all the segments of the AN. A surgical clip was placed at the most proximal and anterior segment of the AN that could be visualized with the arthroscope. A standard open deltopectoral approach was then performed to determine the exact location of the surgical clip and its relation to the origin of the AN.

RESULTS

All segments of the AN (including the blind zone) were visualized from the quadrilateral space to their origin from the posterior cord in all four specimens. The surgical clip was found at an average of 1 cm (range from 0.5 to 1.5 cm) from the origin of the AN from the posterior cord.

CONCLUSIONS

This cadaveric study shows that it is feasible to visualize all segments of the AN (including the blind zone) using this novel approach that combines the use of the standard posterior approach to the AN with dry arthroscopic exploration. Clinical studies are necessary to evaluate the utility of this novel approach.

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.

[Intramedullary nailing vs. locking plate osteosynthesis in proximal humeral fractures: Long-term outcome]

BACKGROUND

For the treatment of proximal humeral fractures two major therapeutic principles can be employed: intramedullary nailing (PHN) or locking plate osteosynthesis. The aim of this study was to evaluate and compare clinical and radiological long-term outcome of proximal humeral fracture stabilization using PHN or angular stable plating.

MATERIALS AND METHODS

In a retrospective study between March 2009 and March 2010, we analyzed 72 out of 118 patients with unified proximal humeral fracture who had been treated at least 3 years previously using PHN (44 patients) or angular stable plating (28 patients) in a level 1 trauma center. Functional and radiological outcomes were assessed at least 3 years after trauma using the Constant and Murley score and SF-36 score.

RESULTS

According to the Neer classification, there were 31 3-part fractures (PHN: 23; plate: 8) and 41 4-part fractures (PHN: 21; plate: 20), respectively. No clinical symptoms after 3 years were observed in 42 patients, whereas in 30 patients clinical symptoms were evaluated related to pain and/or loss of function. Functional outcome using the Constant and Murley score demonstrated a total score of 73 points (ipsilateral side) vs. 88 points (contralateral side) in all evaluated patients, on average.

CONCLUSION

Both PHN and angular stable plating are adequate treatment options for proximal humeral fractures. Both systems require precise preoperative planning and advanced surgical experience. No significant differences in long-term clinical and radiological outcome between implants regarding fracture classification, age of patient, and choice of implant were found.

Accurate application of a precontoured-locking plate for proximal humeral fractures in Asians: a cadaveric study

OBJECTIVES

The purpose of this study was to identify the optimal position for a precontoured-locking plating (PHILOS(®)) of the proximal humerus in Asians in terms of conformity and to determine the prevalence of screw exits in the position of the highest conformity.

METHODS

Twenty adult humeri and 14 cadaveric shoulders were included in this study. After placing the precontoured plate in the well-fitted position on the humerus, we measured the distance between the upper margin of the plate and the tip of greater tuberosity (GT) (distance A) and the distance between the anterior margin of the plate and lateral border of the bicipital groove (BG) (distance B). The prevalence of K-wire exits was assessed. In the 14 cadaver shoulders, the mutual relation between the most inferior locking sleeve of the optimally positioned plate and the axillary nerve was evaluated to assess the potential for axillary nerve injury.

RESULTS

The precontoured plate was well-fitted and remained in a relatively constant position in all specimens. Distance A was an average of 3.6 mm (range 1.4-5.5 mm), and distance B was an average of 2.5 mm (range 0-4.6 mm). The K wire closest to the BG pierced it in four cases (20 %), and most inferior K wires exited at an average distance of 3.8 mm (range 1.6-9.0 mm) from the inferior articular margin of the humeral head. Regarding involvement of the BG, articular width was the only significant variable in the logistic regression model, with an odds' ratio of 0.610. The axillary nerve was located at an average vertical distance of 59.7 mm (range 51.8-66.9 mm) from the tip of the GT in a vertically neutral position. The results did not differ between the left and right sides (t = 0.326, p = 0.755). Although the axillary nerve was slightly inferior to the most inferior locking holes of the proximal humerus, it was located in the path of their locking sleeves on the deltoid muscle.

CONCLUSION

The optimal position for the highest conformity led to ideal fixation of the proximal humerus and inferomedial support screw in Asians. However, the precontoured plate sometimes had screw exits that involved the BG, and articular width had a large impact on involvement of the BG. If locking sleeves for the most inferior holes were introduced on the deltoid muscle in a neutral position, there was high potential for injury to the axillary nerve in Koreans.

Outcome Analysis of Locking Plate Fixation in Proximal Humerus Fracture

INTRODUCTION

Proximal humerus fractures account for approximately 5% of all fractures. Stable minimally displaced fractures can be treated nonoperatively but the management of displaced fractures remain controversial with various modalities of treatment available. Locking plates provide stable fixation and enable early postoperative mobilization specially in osteoporotic proximal humerus fracture.

AIM

To evaluate the functional outcome of locking plate fixation and to compare the results of two approaches used for fixation.

MATERIALS AND METHODS

This prospective study was conducted at a tertiary level hospital between September 2011 to December 2013. PHILOS plates were used for internal fixation of displaced proximal humerus fractures Neer's type 2 part, 3 part and 4 part fractures on 26 patients (M/F ratio 1.36:1; mean age 46 years). According to Neer classification, 5,12 and 9 patients had displaced 2, 3 and 4 part fractures respectively. Deltopectoral and deltoid splitting approaches were used for fixation on 13 patients each. Functional outcome was assessed using Constant-Murley shoulder score. Graphpad software version 6.0 was used with Chi-square test and Fisher-exact test are used to compare data. The p-value< 0.05 is considered significant.

RESULTS

Of the 26 patients, all fractures united radiologically and clinically and average constant score at final follow-up was 72.5. At the final follow-up 8 patients had good score, 10 patients had moderate score, 6 patients had excellent outcome and 2 patients had poor outcome according to Constant score. Mean time to union was 12.3 weeks (9 -15 weeks). Four complications (15.4%) were encountered, 2 cases of varus malunion, 1 case of wound infection which required wound debridement and 1 case of screw cut-out in which screw removal was done. Mean constant score in delto splitting approach was 70.9 and 74 in deltopectoral group (p-value= 0.54). No significant difference existed in constant score in 2 approaches. No significant difference existed between groups in terms of complications (P > .05) and all fractures were united.

CONCLUSION

Our study demonstrates that locking plate fixation gives good functional outcomes in treatment of proximal humerus fractures. There was no significant difference in the two approaches used for exposure. Our results are comparable to various studies conducted by other authors which states that locking plates provide better functional and radiological outcomes as compared to other fixation methods like Tension band wiring, percutaneous K-wire fixation, non-locking plates, intramedullary nails.

A brief history of topographical anatomy

This brief history of topographical anatomy begins with Egyptian medical papyri and the works known collectively as the Greco-Arabian canon, the time line then moves on to the excitement of discovery that characterised the Renaissance, the increasing regulatory and legislative frameworks introduced in the 18th and 19th centuries, and ends with a consideration of the impact of technology that epitomises the period from the late 19th century to the present day. This paper is based on a lecture I gave at the Winter Meeting of the Anatomical Society in Cambridge in December 2015, when I was awarded the Anatomical Society Medal.

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.