The anatomic relationships of the axillary nerve and surgical landmarks for its localization from the anterior aspect of the shoulder

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 morphology of the subacromial and related shoulder bursae. An anatomical and histological study

Shoulder bursae are essential for normal movement and are also implicated in the pathogenesis of shoulder pain and dysfunction. The subacromial bursa (SAB), within the subacromial space, is considered a primary source of shoulder pain. Several other bursae related to the subcoracoid space, including the coracobrachial (CBB), subcoracoid (SCB) and subtendinous bursa of subscapularis (SSB), are also clinically relevant. The detailed morphology and histological characteristics of these bursae are not well described. Sixteen embalmed cadaveric shoulders from eight individuals (five females, three males; mean age 78.6 ± 7.9 years) were investigated using macro-dissection and histological techniques to describe the locations, dimensions and attachments of the bursae, their relationship to surrounding structures and neurovascular supply. Bursal sections were stained with haematoxylin and eosin to examine the synovium and with antibodies against von Willebrand factor and neurofilament to identify blood vessels and neural structures respectively. Four separate bursae were related to the subacromial and subcoracoid spaces. The SAB was large, with a confluent subdeltoid portion in all except one specimen, which displayed a distinct subdeltoid bursa. The SAB roof attached to the lateral edge and deep surface of the acromion and coracoacromial ligament, and the subdeltoid fascia; its floor fused with the supraspinatus tendon and greater tubercle. The CBB (15/16 specimens) was deep to the conjoint tendon of coracobrachialis and short head of biceps brachii and the tip of the coracoid process, while the inconstant SCB (5/16 specimens) was deep to the coracoid process. Located deep to the subscapularis tendon, the SSB was a constant entity that commonly displayed a superior extension. Synovial tissue was predominantly areolar (SAB and SSB) or fibrous (CBB and SCB), with a higher proportion of areolar synovium in the bursal roofs compared to their floors. Blood vessels were consistently present in the subintima with a median density of 3% of the tissue surface area, being greatest in the SSB and SAB roofs (4.9% and 3.4% respectively) and least in the SAB floor (1.8%) and CBB roof and floor (both 1.6%). Nerve bundles and free nerve endings were identified in the subintima in approximately one-third of the samples, while encapsulated nerve endings were present in deeper tissue layers. The extensive expanse and attachments of the SAB support adoption of the term subacromial-subdeltoid bursa. Morphologically, the strong attachments of the bursal roofs and floors along with their free edges manifest as fixed and mobile portions, which enable movement in relation to surrounding structures. The presence of neurovascular structures demonstrates that these bursae potentially contribute blood supply to surrounding structures and are involved in mechanoreception. The anatomical details presented in this study clarify the morphology of the shoulder bursae, including histological findings that offer further insight into their potential function.

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.

Associated Pathologies following Luxatio Erecta Humeri: A Retrospective Analysis of 38 Cases

Inferior shoulder dislocation in fixed abduction, also known as luxatio erecta humeri (LEH), is a rare injury with little data available. Therefore, the primary aim of this study was to evaluate and present our case series of this type of injury with special emphasis on associated pathologies; the secondary aim was to present diagnostic recommendations to detect for potential associated pathologies typically seen with this injury. A total of 38 patients (13 females, average age 72.8 years and 25 males, average age 41.4 years), who have been treated for inferior shoulder dislocation between 1992 and 2020, were included in this study. Associated pathologies after LEH were found in 81% of the cases. Twenty-one of these patients presented with secondary bony pathologies. Six patients revealed rotator cuff injuries diagnosed by magnetic resonance imaging (MRI). Seven patients exhibited pathological findings at the capsule-ligament complex. Eight patients presented with neurological findings. All neurologic symptoms except one axillary nerve palsy and a radialis paresis dissolved during the follow-up period. Five patients received surgical treatment of the affected shoulder. Inferior shoulder dislocation is a rare condition presenting with a high number of associated injuries. According to the findings of the present study, we want to raised awareness of the high rate of potential secondary shoulder pathologies associated with LEH. Beside a thorough clinical examination and immediate standard radiographs in two planes, we recommend to perform computed tomography scanning and an MRI of the shoulder as soon as possible. In the case of neurologic deficiencies, a determination of nerve conduction should be performed.

What Are Practical Surgical Anatomic Landmarks and Distances from Relevant Neurologic Landmarks in Cadavers for the Posterior Approach in Shoulder Arthroplasty?

BACKGROUND

Traditional total shoulder arthroplasty is performed through the deltopectoral approach and includes subscapularis release and repair. Subscapularis nonhealing or dysfunction may leave patients with persistent pain, impairment, and instability. Alternative approaches that spare the subscapularis include rotator interval and posterior shoulder approaches; however, to our knowledge, a cadaveric study describing pertinent surgical anatomy for a posterior shoulder approach regarding shoulder arthroplasty has not been performed.

QUESTIONS/PURPOSES

(1) What are the distances from important neurologic structures of the shoulder for arthroplasty through a posterior approach? (2) What surgical landmarks can help identify the internervous interval between the infraspinatus and teres minor?

METHODS

Twelve hemitorso cadaver specimens with intact rotator cuffs were dissected to study posterior shoulder anatomy regarding posterior shoulder arthroplasty. The median (range) age of the specimens was 79 years (55 to 92). Six of the 12 specimens were right-hand dominant, and 10 specimens were male. Cadaver height was a median 171 cm (155 to 191) and weight was a median of 68 kg (59 to 125). A posterior deltoid split and internervous approach between the infraspinatus and teres minor were used. A posterior T capsulotomy was performed. The distances to important neurologic structures were measured with an electronic caliper and provided in median (range) distances in millimeters. Although not as meaningful as distance ratios accounting for a specimen's body size, neurologic distances in millimeters are surgically practical and provide intraoperative usefulness. Surgical landmarks that can help identify the infraspinatus and teres minor plane were noted. Practical visual and tactile cues between the infraspinatus and teres minor were identified. Posterior rotator cuff tendon morphologies and widths were recorded.

RESULTS

The closest important neurologic structure was the axillary nerve, measuring a median (range) 17 mm (9 to 19) from the inferior glenoid rim while the infraspinatus branch of the suprascapular nerve measured 21 mm (15 to 36) from the posterior glenoid rim. The axillary nerve measured 84 mm (70 to 97) from the posterior tip of the acromion in the deltoid split. Three surgical landmarks were helpful for identifying the plane between the infraspinatus and teres minor in all 12 specimens: (1) identifying the triangular teres minor tendon insertion, (2) medial palpation identifying the low point between the prominent muscle bellies of the infraspinatus and teres minor, and (3) identifying the distinct and prominent teres minor tubercle, which is well localized and palpable.

CONCLUSION

A major benefit of the posterior approach for shoulder arthroplasty is subscapularis preservation. Multiple practical surgical cues are consistently present and can help identify the infraspinatus and teres minor interval. We did not find the presence of fat stripes to be helpful. The suprascapular nerve is in proximity to posterior surgical dissection and differs from the deltopectoral approach. This is an important distinction from an anterior approach and requires care with dissection. Future studies are necessary to assess iatrogenic risk to the posterior rotator cuff and external rotation strength. This may entail intraoperative nerve conduction studies of the posterior rotator cuff and clinical studies assessing external rotation strength.

CLINICAL RELEVANCE

Studying posterior shoulder anatomy is an initial first step to assessing the feasibility of the posterior approach for anatomic shoulder arthroplasty. Additional studies assessing the degree of glenohumeral exposure and possible iatrogenic posterior rotator cuff injury are necessary. Because of the proximity of neurologic structures, it is recommended that surgeons not perform this technique until sufficient evidence indicates that it is equivalent or superior to standard anterior approach total shoulder arthroplasty. After such evidence is available, proper training will be necessary to ensure safe use of the posterior shoulder approach.

Modified Arthroscopic Latarjet Procedure: Button Fixation Without Splitting of the Subscapularis

The Latarjet procedure is used for the treatment of anterior glenohumeral instability in the presence of bone loss. One decade after a fully arthroscopic Latarjet procedure was described, this technique has been modified to reduce the risk of complications and improve the fixation method. We aimed to simplify the components of this surgical procedure.

Automated Nerve Monitoring in Shoulder Arthroplasty: A Prospective Randomized Controlled Study

BACKGROUND

Evoked potential monitoring is believed to prevent neurologic injury in various surgical settings; however, its clinical effect has not been scrutinized. It was hypothesized that an automated nerve monitor can minimize intraoperative nerve injury and thereby improve clinical outcomes in patients undergoing shoulder arthroplasty.

METHODS

A prospective, blinded, parallel group, superiority design, single-center, randomized controlled study was conducted. Study participants were equally randomized into either the automated nerve-monitored or the blinded monitored groups. The primary outcome was intraoperative nerve injury burden as assessed by the cumulative duration of nerve alerts. Secondary outcomes were neurologic deficits and functional scores of the operative arm, and the quality of life index (Euro Quality of life-5 domain-5 level score) at postoperative weeks 2, 6, and 12.

RESULTS

From September 2018 to July 2019, 213 patients were screened, of whom 200 were randomized. There was no statistically significant difference in the duration of nerve alerts between the automated nerve-monitored and control groups (median [25th, 75th interquartile range]: 1 [0, 18] and 5 [0, 26.5]; Hodges-Lehman difference [95% CI]: 0 [0 to 1] min; P = 0.526). There were no statistically significant differences in secondary outcomes between groups. However, in the ancillary analysis, there were reductions in neurologic deficits and improvements in quality of life index occurring in both groups over the course of the study period.

CONCLUSIONS

Protection from nerve injury is a shared responsibility between surgeons and anesthesiologists. Although a progressive improvement of clinical outcomes were observed over the course of the study in both groups as a consequence of the real-time feedback provided by the automated nerve monitor, this trial did not demonstrate that automated nerve monitoring by itself changes important clinical outcomes compared with no monitoring.

EDITOR’S PERSPECTIVE

Neurologic complications in primary anatomic and reverse total shoulder arthroplasty: A review

Neurologic injury during shoulder replacement is one of the less common complications of the procedure, however the clinical implications can be significant. The purpose of this paper is to review the current literature on neurologic complications in various types of shoulder replacement and provide recommendations regarding avoidance, evaluation, and management of these complications.

Prevention and Treatment of Nerve Injuries in Shoulder Arthroplasty

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

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

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

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Risk of Iatrogenic Axillary Nerve Injury During Acromioclavicular Joint Reconstruction

Anatomical reconstruction of the coracoclavicular ligaments involves drilling the base of the coracoid or looping a graft around it, placing the axillary nerve at risk for injury. Rockwood type V acromioclavicular (AC) separation injuries involve disruption of the AC joint capsule and coracoclavicular ligaments, resulting in inferomedial displacement of the scapulohumeral complex and alteration of the normal anatomical relations of the shoulder girdle structures. This study evaluated the effect of Rockwood type V AC separation on the anatomical relation of the axillary nerve to the coracoid base. Ten shoulders of 6 adult human cadavers were dissected to determine the dimensions of the coracoid. A digital caliper was used to measure the coracoclavicular distance and the minimal distance between the coracoid base and the axillary nerve. A Rockwood type V AC separation was created by transecting the AC joint capsule and coracoclavicular ligaments, and applying 15 kg of longitudinal tension to the upper extremity. Changes in the distance between the coracoid base and the axillary nerve were measured. Mean width, length, and thickness of the coracoid was 15.05±0.93 mm, 23.1±1.75 mm, and 11.88±1.33 mm, respectively. Mean distance between the coracoid base and the axillary nerve was 26.0±3.9 mm. After simulated Rockwood type V AC separation, mean distance was 22.0±3.4 mm; this difference was statistically significant (P=.0263; 95% CI, 2.0-5.9 mm). The axillary nerve is closer to the coracoid base during simulated Rockwood type V AC separation than previously reported in the orthopedic literature. Anatomical reconstruction of the coracoclavicular ligaments for Rockwood type V AC separation presents a higher risk for axillary nerve iatrogenic injury than previously reported. [Orthopedics. 2021;44(1):e68-e72.].

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.

Intraoperative neuromonitoring during reverse shoulder arthroplasty

BACKGROUND

The aim of this study was to evaluate the risk of nerve injury with neuromonitoring during reverse total shoulder arthroplasty.

MATERIALS

This study included 15 shoulders of 15 patients (11 females and 4 males) who underwent reverse total shoulder arthroplasty. The mean age was 74.8 ± 4.4 years. Nine shoulders had cuff tear arthropathy, 4 had massive rotator cuff tears, 2 had osteoarthritis, and 1 had rheumatoid arthritis. The somatosensory evoked potentials of the median nerve, transcranial motor evoked potentials, and free-electromyograms from 6 upper-extremity muscles were measured intraoperatively. We defined a nerve alert as 50% amplitude attenuation or 10% latency prolongation of the somatosensory evoked potentials and transcranial motor evoked potentials and sustained neurotonic discharge on free-electromyogram.

RESULTS

Thirty-one alerts were recorded in 11 patients. The axillary nerve was associated with 17 alerts. Eleven alerts occurred during the glenoid procedure and 5 alerts occurred during the humeral procedure. One patient who did not recover from the alert of the axillary nerve had clinically incomplete paralysis of the deltoid muscle.

CONCLUSION

The present findings suggest that the axillary nerve was the nerve most frequently exposed to the risk of injury, especially during glenoid and humeral implantation.

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.

Incidence of clinically evident isolated axillary nerve injury in 869 primary anatomic and reverse total shoulder arthroplasties without routine identification of the axillary nerve

Background

It has been suggested that, during primary shoulder arthroplasty, surgeons should identify the axillary nerve through direct visualization, palpation, or the “tug test” to prevent iatrogenic nerve injury. Our goal was to document the rate of isolated axillary nerve injury (IANI) in patients who had undergone primary anatomic total shoulder arthroplasty (TSA) or reverse total shoulder arthroplasty (RTSA) without routine identification of the axillary nerve.

Methods

Data on 869 cases of primary shoulder arthroplasty (338 TSAs and 531 RTSAs) performed by 1 surgeon between 2003 and 2017 were reviewed. Neither the tug test nor identification of the axillary nerve through palpation or visualization was used in any case. The primary outcome was new IANI documented within 3 months after arthroplasty. The frequency of IANI was summarized using point estimates and 95% confidence intervals (CIs).

Results

Six cases met the criteria for IANI. The overall incidence of IANI was 0.7% (95% CI, 0.3%-1.4%). The incidence of IANI was 0.3% (95% CI, 0%-1.6%) after TSA and 0.9% (95% CI, 0.3%-2.1%) after RTSA. All IANIs were cases of neurapraxia, and all patients had experienced complete neurologic recovery at last follow-up.

Conclusion

Complete, permanent IANI resulting from direct surgical trauma during primary shoulder arthroplasty can be avoided without using the tug test or routine identification of the nerve. A low incidence of partial temporary IANI can be expected, which may be related to indirect traction injuries.

Reverse shoulder arthroplasty in recent proximal humerus fractures

Reverse shoulder arthroplasty is now the standard treatment for displaced, three- or four-part, proximal humeral fractures in patients older than 70 years. Inadequate tuberosity repair or inappropriate humeral stem position are associated with poorer outcomes, notably regarding rotation and stability. Strict operative technique during prosthesis implantation is therefore crucial to obtain reliable and reproducible outcomes. The objective of this article is to describe the surgical technique for reverse shoulder arthroplasty used to treat recent proximal humerus fractures.

Influence of age, gender, and radiographic features on the deltoid splitting approach for surgical osteosynthesis in displaced proximal humerus fractures: a comparison study

BACKGROUND

The deltoid splitting approach has recently been widely adopted to facilitate less invasive procedures for proximal humerus fractures. However, there are still concerns regarding its effectiveness in aging people and in cases involving complex fractures. This study was conducted to evaluate the efficacy of a proximal humeral locking plate using the anterolateral deltoid splitting approach and to specifically examine the effect of patient age, gender, and fracture pattern on surgical outcomes.

METHODS

Forty-two cases of proximal humeral fractures treated using the deltoid splitting approach and locking plate fixation were reviewed. Outcome differences were evaluated in terms of age, gender distribution, and radiographic analysis based on the Neer Classification. The influence of the surgical approach was further investigated by age-matched paired analysis after subdividing patients into two age groups (younger than 60 years vs. older than 60 years; N = 21, in each group).

RESULTS

In total, 41 patients (98%) demonstrated fracture union. The average Constant score was 80.4. No significant differences were found between patients younger than 60 years, and the older patients. Higher mean scores were found in men than in women (p = 0.448) and in simple fractures than in complex fractures (p = 0.454), without any significant differences. Better postoperative functional outcomes were observed when the humeral head-neck angle was greater than 105°, with a significant difference (p = 0.000). Surgical complications were found in 16 patients (38%) without significant difference between two age groups (p = 0.268). The most common complication was screw penetration.

CONCLUSIONS

Anterolateral deltoid splitting using locking plate fixation provided a feasible alternative for surgery of proximal humerus fractures in different age groups and yielded comparable outcomes when the neck-shaft angle was properly restored. Surgeons must be cautious regarding potential complications, especially with screw penetration when using the locking plate through a less invasive approach.

TRIAL REGISTRATION

ISRCTN75494532 . Trial Date: 2017/01/31.

The risk of suprascapular and axillary nerve injury in reverse total shoulder arthroplasty: An anatomic study

PURPOSE

Implantation of a reverse total shoulder arthroplasty (rTSA) places the axillary and suprascapular nerves at risk. The aim of this anatomic study was to digitally analyse the location of these nerves in relation to bony landmarks in order to predict their path and thereby help to reduce the risk of neurological complications during the procedure.

METHODS

A total of 22 human cadaveric shoulder specimens were used in this study. The axillary and suprascapular nerves were dissected, and radiopaque threads were sutured onto the nerves without mobilizing the nerves from their native paths. Then, 3D X-ray scans of the specimens were performed, and the distance of the nerves to bony landmarks at the humerus and the glenoid were measured.

RESULTS

The distance of the inferior glenoid rim to the axillary nerve averaged 13.6mm (5.8-27.0mm, ±5.1mm). In the anteroposterior direction, the distance between the axillary nerve and the humeral metaphysis averaged 8.1mm (0.6-21.3mm, ±6.5mm). The distance of the glenoid centre to the suprascapular nerve passing point under the transverse scapular ligament measured 28.4mm (18.9-35.1mm, ±3.8mm) in the mediolateral direction and 10.8mm (-4.8 to 25.3mm, ±6.1mm) in the anteroposterior direction. The distance to the spinoglenoid notch was 16.6mm (11.1-24.9mm, ±3.4mm) in the mediolateral direction and -11.8mm posterior (-19.3 to -4.7mm, ±4.7mm) in the anteroposterior direction.

CONCLUSIONS

Implantation of rTSA components endangers the axillary nerve because of its proximity to the humeral metaphysis and the inferior glenoid rim. Posterior and superior drilling and extraosseous screw placement during glenoid baseplate implantation in rTSA place the suprascapular nerve at risk, with safe zones to the nerve passing the spinoglenoid notch of 11mm and to the suprascapular notch of 19mm.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Cadaveric study, Level V.

Nerve stress during reverse total shoulder arthroplasty: a cadaveric study

BACKGROUND

Neurologic lesions are relatively common after total shoulder arthroplasty. These injuries are mostly due to traction. We aimed to identify the arm manipulations and steps during reverse total shoulder arthroplasty (RTSA) that affect nerve stress.

METHODS

Stress was measured in 10 shoulders of 5 cadavers by use of a tensiometer on each nerve from the brachial plexus, with shoulders in different arm positions and during different surgical steps of RTSA.

RESULTS

When we studied shoulder position without prostheses, relative to the neutral position, internal rotation increased stress on the radial and axillary nerves and external rotation increased stress on the musculocutaneous, median, and ulnar nerves. Extension was correlated with increase in stress on all nerves. Abduction was correlated with increase in stress for the radial nerve. We identified 2 high-risk steps during RTSA: humeral exposition, particularly when the shoulder was in a position of more extension, and glenoid exposition. The thickness of polyethylene humeral cups used was associated with increased nerve stress in all but the ulnar nerve.

CONCLUSION

During humeral preparation, the surgeon must be careful to limit shoulder extension. Care must be taken during exposure of the glenoid. Extreme rotation and oversized implants should be avoided to minimize stretch-induced neuropathies.

Axillary nerve course and position in the fetal period. An anatomic dissection study for surgical practice

OBJECTIVE

To examine the fetal axillary nerve to reveal and compare its morphometric features within the second and third trimester.

METHODS

This study was conducted at the Anatomy Department, School of Medicine, Mersin University, Mersin, Turkey. Thirty-five fetal shoulders were studied to provide anatomic data and to describe its position with regard to certain landmarks around the shoulder.

RESULTS

The shortest distance between the axillary nerve and the glenoid labrum was found 2.27 mm and 2.89 mm in the second and third trimester fetuses, respectively. The shortest distances between the anterior and posterior acromial tips and the axillary nerve were also measured and were used with arm length measurements to define the anterior and posterior indexes.

CONCLUSION

The indexes show that the distance between the axillary nerve and the anterior/posterior acromial tips are approximately one-fourth of the arm length in both the second and third trimester fetuses. The data presented in this study will be of use to surgeons, particularly to pediatric and orthopedic surgeons who will undertake surgical procedures in the axilla and arm in the newborn or early childhood.

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.

Deltopectoral approach for shoulder arthroplasty: anatomic basis

PURPOSE

The deltopectoral approach is a common surgical procedure for shoulder arthroplasty. Many surgeons are familiar with this procedure, but certain steps are still controversial. This is the case for the management of subscapularis, where surgeons must choose between tenotomy and the lesser tuberosity osteotomy.

METHODS

This article is conceived as a toolkit for the inexperienced surgeons, describing our tips and tricks to facilitate final exposure of the glenoid. For experienced surgeons, we analysed the tricky portions of the deltopectoral approach, comparing them with what is classically reported in the literature.

RESULTS

We describe an original technic for subscapularis reattachment after lesser tuberosity osteotomy in order to improve its stability. The medial part of the fragment is secondarily sculpted to obtain a step shape, which will be applied against the base of the prosthetic cup in a sort of "corner buttress".

CONCLUSIONS

Our work, based on our personal experience, confirms that there is no preferred single deltopectoral approach but, rather, multiple options. When embarking on this "shoulder highway", we encourage surgeons to respect the successive anatomic planes, which we believe is the only way to ensure easy and atraumatic dissection.

KEY POINTS

- The safe plane for going around the humeral head and positioning retractors is the plane of the subacromial deltoid bursa. - Always stay close to the bone during capsule release, whether on the humeral or glenoid side. - Never go medially to the conjoint tendon or its deep face.

Quantification of the exposure of the glenohumeral joint from the minimally invasive to more invasive subscapularis approach to the anterior shoulder: a cadaveric study

BACKGROUND

There are multiple techniques to approach the glenohumeral joint. Our purpose was to quantify the average area of the glenohumeral joint exposed with 3 subscapularis approaches and determine the least invasive approach for placement of shoulder resurfacing and total shoulder arthroplasty instruments.

METHODS

Ten forequarter cadaveric specimens were used. Subscapularis approaches were performed sequentially from split, partial tenotomy, and full tenotomy through the deltopectoral approach. Glenohumeral joint digital photographs were analyzed in Image J software (National Institutes of Health, Bethesda, MD, USA). Shoulder resurfacing and total shoulder arthroplasty instruments were placed on the humeral head, and anatomic landmarks were identified.

RESULTS

The average area of humeral head visible, from the least to the most invasive approach, was 3.2, 8.1, and 11.0 cm2, respectively. The average area of humeral head visible differed significantly according to the approach. Humeral head area increased 157% when the subscapularis split approach was compared with the partial tenotomy approach and 35% when the partial approach was compared with the full tenotomy approach. The average area of glenoid exposed from least to most invasive approach was 2.0, 2.3, and 2.5 cm2, respectively. No significant difference was found between the average area of the glenoid and the type of approach. Posterior structures were difficult to visualize for the subscapularis split approach. Partial tenotomy of the subscapularis allowed placement of resurfacing in 70% of the specimens and total arthroplasty instruments in 90%.

CONCLUSIONS

The subscapularis splitting approach allows adequate exposure for glenoid-based procedures, and the subscapularis approaches presented expose the glenohumeral joint in a step-wise manner.

LEVEL OF EVIDENCE

Anatomy study, cadaver dissection.

Surgical anatomy of the axillary nerve branches to the deltoid muscle

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

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

BACKGROUND

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

LEVEL OF EVIDENCE

Basic science study, cadaver study.

The arthroscopic "subdeltoid approach" to the anterior shoulder

Surgical management of shoulder pathologies has evolved tremendously during the past 3 decades, such that many lesions previously treated with open techniques are now addressed arthroscopically. Despite this movement, many surgeons and outcome studies continue to prefer open repairs as the gold standard, criticizing--with good reason--the reliability, reproducibility, and extended operative time of arthroscopic repairs, particularly with respect to anterior stabilizations and subscapularis repairs. With this in mind, we present the arthroscopic "subdeltoid approach," a novel standardized exposure technique for extracompartmental anterior shoulder arthroscopy. We define the subdeltoid space as the fascial plane bound superiorly by the acromion and coracoacromial ligament, medially by the coracoid and the conjoint tendon, inferiorly by the musculotendinous insertion of the pectoralis major to the humerus, and laterally by the lateral border of the humerus. When coupled with existing arthroscopic tools, this space dramatically enhances our ability to apply open techniques to some of the more challenging anterior shoulder pathoanatomy and expand the indications and efficacy of arthroscopy. This exposure technique has been used in more than 300 cases during the past decade to treat a myriad of shoulder pathologies, without any longstanding postoperative complications.

Motor nerve lengths of twenty-seven muscles in upper extremity

The purpose of this study is to determine the lengths of motor nerves in the upper extremity. Motor nerves of 27 muscles in 10 cadavers (16 extremities) were dissected from their roots at the level of intervertebral foramen to the entry point of the nerves to the corresponding muscles. Distance between acromion and the lateral epicondyle of the humerus was also measured in all cadavers. Nerve length of the coracobrachialis muscle was the shortest (18.26 ± 1.64 cm), while the longest was the nerve of the extensor indicis (59.51 ± 4.80 cm). The biceps brachii, the extensor digitorum communis, and the brachialis muscles showed highest coefficient of variation that makes these nerve lengths of muscles inconsistent about their lengths. This study also offers quotients using division of the lengths of each nerve to acromion-the lateral epicondyle distance. Knowledge of the nerve lengths in the upper extremity may provide a better understanding the reinnervation sequence and the recovery time in the multilevel injuries such as brachial plexus lesions. Quotients may be used to estimate average lengths of nerves of upper extremity in infants and children. Moreover, reliability of the biceps brachii as a determinant factor for surgery in obstetrical brachial plexus lesions should be reconsidered due to its highest variation coefficient.

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.

Anatomical considerations of subcoracoid neurovascular structures in anterior shoulder reconstruction

Anterior shoulder surgery, using open or arthroscopic technique, places subcoracoid neurovasculature at risk. This study examines the relationships of the brachial plexus and axillary artery to four bony landmarks and provides clinical correlations for anterior shoulder surgery. The musculocutaneous nerve (MN), posterior cord (PC), lateral cord (LC), and axillary artery (AA) were identified in 27 shoulders. Minimum distances (mm) were measured between neurovasculature and the coracoid tip, anterior midglenoid, inferior surface of the midclavicle, and anteromedial aspect of the acromioclavicular joint. Average distances from the coracoid to the MN, PC, LC, and AA were 69.7 ± 31.6, 50.5 ± 9.2, 41.8 ± 9.4, and 60.0 ± 8.0 mm, respectively; from the glenoid equator to the MN, PC, LC, and AA were 61.5 ± 38.5, 37.0 ± 6.1, 35.2 ± 8.7, and 45.2 ± 7.1 mm, respectively; from the midclavicle to the MN, PC, LC, and AA were 114.1 ± 33.9, 62.0 ± 13.6, 56.0 ± 19.7, and 69.9 ± 7.8 mm, respectively; and from the AC joint to the MN, PC, LC, and AA were 112.7 ± 36.5, 87.9 ± 10.6, 84.0 ± 12.0, and 100.9 ± 1.0 mm, respectively. The lateral cord was the closest structure to each bony landmark. The musculocutaneous nerve was the furthest structure from each bony landmark. Open procedures using a deltopectoral approach with the shoulder in the anatomical position, such as the Neer capsular shift and Warner capsular reconstruction, can use these results to prevent direct or retraction injuries. Results indicate a potential safe zone of 30 mm in diameter around the anteromedial coracoid tip for anteroinferior portal placement.

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.

Automated identification of anatomical landmarks on 3D bone models reconstructed from CT scan images

Identification of anatomical landmarks on skeletal tissue reconstructed from CT/MR images is indispensable in patient-specific preoperative planning (tumour referencing, deformity evaluation, resection planning, and implant alignment and anchoring) as well as intra-operative navigation (bone registration and instruments referencing). Interactive localisation of landmarks on patient-specific anatomical models is time-consuming and may lack in repeatability and accuracy. We present a computer graphics-based method for automatic localisation and identification (labelling) of anatomical landmarks on a 3D model of bone reconstructed from CT images of a patient. The model surface is segmented into different landmark regions (peak, ridge, pit and ravine) based on surface curvature. These regions are labelled automatically by an iterative process using a spatial adjacency relationship matrix between the landmarks. The methodology has been implemented in a software program and its results (automatically identified landmarks) are compared with those manually palpated by three experienced orthopaedic surgeons, on three 3D reconstructed bone models. The variability in location of landmarks was found to be in the range of 2.15-5.98 mm by manual method (inter surgeon) and 1.92-4.88 mm by our program. Both methods performed well in identifying sharp features. Overall, the performance of the automated methodology was better or similar to the manual method and its results were reproducible. It is expected to have a variety of applications in surgery planning and intra-operative navigation.

Effects of the adducted or abducted position of the arm on the course of the musculocutaneous nerve during anterior approaches to the shoulder

Nerve injury is a common complication during anterior shoulder surgery. The purpose of the study was to evaluate the musculocutaneous nerve (MN) anatomically and to clarify the relationship of the MN to the glenoid labrum and coracoid process in different arm positions. The study was carried out on 40 shoulders of 20 adult cadavers fixed in 10% formaldehyde. The minimum distance of the MN at the entrance point of the nerve into the coracobrachialis to the anteromedial aspect of the coracoid tip and the distance between the MN and the top, middle, and inferior points of the glenoid labrum were measured. All measurements were performed with a digital caliper while the arm was in a neutral position, 45 degrees and 90 degrees of abduction, 90 degrees of abduction-internal rotation and 90 degrees of abduction-external rotation to evaluate whether arm position effects the results statistically or not. The results demonstrated that the position of the arm significantly changes the distance between the coracoid process (CP) and the MN or its cord. The change in distance between the glenoid labrum and the MN or its cord was also statistically significant. The distance between the CP and MN was greatest when the arm was abducted to 45 degrees (mean 3.4 cm) and least when the arm was positioned to 90 degrees of abduction-internal rotation (mean 2.0 cm). While the distance between the MN and the coracoid process was least at 90 degrees of abduction and internal rotation, the distance between the MN and glenoid labrum was lest with 90 degrees of abduction and external rotation. The distance between the glenoid labrum and MN was greatest with 45 degrees of abduction. The results of this study might be of use in avoiding the MN especially during Bristlow operations and certain rotator cuff procedures. Transferring the coracoid process during Bristow operations or placing arthroscopic portals when the arm is abducted to 45 degrees appears to be the safest position in terms of MN injury. Based on our results, when the arm needs to be abducted to 90 degrees during operation, externally rotating it may decrease the tension on the brachial plexus thus increasing the distance between the MN and the portals or retractors.

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.

The surgical approach for locking plate osteosynthesis of displaced proximal humeral fractures influences the functional outcome

This study evaluated the influence of the surgical approach for locking plate osteosynthesis in proximal humeral fractures during a 1-year period. We performed a comparative study in 83 patients to evaluate possible benefits for an early functional result for function, pain, activity levels, radiographic evaluation, and complications. In 39 cases, the extended anterolateral deltoid-splitting approach was used (group DS); in 44 cases, the deltopectoral approach was used (group DP). The clinical and radiologic follow-up took place 3, 6, and 12 months after the operation. The functional results in the adjusted Constant score after 3 months showed higher values for group DS of 57.9% vs group DP with 49.6%. After 6 months, no significant differences were seen, with 69.4% for group DS and 71.4% for group DP. Finally, after 12 months, group DP showed higher results at 81% compared with 73.1% for DS. In the subgroups of the Constant score, abduction and active anterior elevation showed particularly higher values in group DP. The duration of the operation was 67 minutes in group DS and 86 minutes in group DP. One case of avascular necrosis was observed in group DS and 3 in group DP. We conclude that the choice of approach for exposure of the proximal humerus region may influence the functional outcome. Stable osteosynthesis is important, but the outcome of operatively treated proximal humerus fractures is dependent on soft tissue management as well.