The anatomic relationship of the brachial plexus and axillary artery to the glenoid. Implications for anterior shoulder surgery

Coracobrachialis muscle morphology and coexisted neural variants: a cadaveric case series

PURPOSE

The current cadaveric case series evaluates the coracobrachialis muscle morphology, the related musculocutaneous nerve origin, course, and branching pattern, as well as associated adjacent neuromuscular variants.

MATERIALS AND METHODS

Twenty-seven (24 paired and 3 unpaired) cadaveric arms were dissected to identify the coracobrachialis possible variants with emphasis on the musculocutaneous nerve course and coexisted neural variants.

RESULTS

Four morphological types of the coracobrachialis were identified: a two-headed muscle in 62.96% (17/27 arms), a three-headed in 22.2% (6/27), a one-headed in 11.1% (3/27), and a four-headed in 3.7% (1 arm). A coracobrachialis variant morphology was identified in 37.04% (10/27). A three-headed biceps brachii muscle coexisted in 23.53% (4/17). Two different courses of the musculocutaneous nerve were recorded: 1. a course between coracobrachialis superficial and deep heads (in cases of two or more heads) (100%, 24/24), and 2. a medial course in case of one-headed coracobrachialis (100%, 3/3). Three neural interconnections were found: 1. the lateral cord of the brachial plexus with the medial root of the median nerve in 18.52%, 2. the musculocutaneous with the median nerve in 7.41% and 3. the radial with the ulnar nerve in 3.71%. Duplication of the lateral root of the median nerve was identified in 11.1%.

CONCLUSIONS

The knowledge of the morphology of the muscles of the anterior arm compartment, especially the coracobrachialis variant morphology and the related musculocutaneous nerve variable course, is of paramount importance for surgeons. Careful dissection and knowledge of relatively common variants play a significant role in reducing iatrogenic injury.

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.

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

Surgical anatomy of the axillary artery: clinical implications for open shoulder surgery

BACKGROUND

Axillary artery injury is a devastating complication related to anterior shoulder surgery and can result in significant morbidity and/or mortality. The purpose of our study was to evaluate the course of the axillary artery in relation to bony landmarks of the shoulder and identify variations in artery position with humeral external rotation.

MATERIALS AND METHODS

Dissection of 18 shoulders (9 fresh whole-body cadavers) with simulated vessel perfusion using radiopaque dye was performed. The axillary artery position was measured from multiple points including 2 points on the coracoid base (C1 and C2), 3 points on the coracoid tip (C3-C5), 4 points on the glenoid: superior, middle, and inferior glenoid (D1-D4), and 2 points on the lesser tuberosity (L1 and L2). Fluoroscopic measurements were taken and compared at 0° and 90° of external rotation (F1 vs. F1' and F2 vs. F2'). Manual and fluoroscopic measurements were compared with one another using Kendall's τ_b correlation.

RESULTS

There were 6 male and 3 female cadavers with an average age of 67.2 ± 9.3 years (range: 49-77 years). The mean distance from the axillary artery to the coracoid base (C1 and C2) measured 21.1 ± 7.3 and 22.3 ± 7.4 mm, respectively, whereas the mean distance to the coracoid tip (C3, C4, and C5) measured 30.7 ± 9.3, 52.1 ± 20.2, and 46.5 ± 14.3 mm, respectively. Measurements relative to the glenoid face (D1, D2, and D3) showed a progressive decrease in mean distance from superior to inferior, measuring 31.6 ± 10.3, 16.5 ± 7.5, and 10.3 ± 7.3 mm, respectively, whereas D4 (inferior glenoid to axillary artery) measured 17.8 ± 10.7 mm. The minimum distance from the axillary artery to any point on the glenoid was as close as 4.1 mm (D3). There was a statistically significant difference in F1 (0° external rotation) vs. F1' (90° external rotation) (18.5 vs. 13.4 mm, P = .03). Kendall's τ_b correlation showed a strong, positive correlation between manual and fluoroscopic measurements (D4: 16.0 ± 12.5 mm vs. F1: 18.5 ± 10.7 mm) (τ_b = 0.556, P = .037).

CONCLUSION

The axillary artery travels an average of 1-1.8 cm from the inferior glenoid margin, which puts the artery at significant risk. In addition, the artery is significantly closer to the inferior glenoid with humeral external rotation. Surgeons performing anterior shoulder surgery should have a thorough understanding of the axillary artery course and understand changes in the position of the artery with external rotation of the humerus.

Complications of reverse shoulder arthroplasty: a concise review

Reverse shoulder arthroplasty is an ideal treatment for glenohumeral dysfunction due to cuff tear arthropathy. As the number of patients treated with reverse shoulder arthroplasty is increasing, the incidence of complications after this procedure also is increasing. The rate of complications in reverse shoulder arthroplasty was reported to be 15%-24%. Recently, the following complications have been reported in order of frequency: periprosthetic infection, dislocation, periprosthetic fracture, neurologic injury, scapular notching, acromion or scapular spine fracture, and aseptic loosening of prosthesis. However, the overall complication rate has varied across studies because of different prosthesis used, improvement of implant and surgical skills, and different definitions of complications. Some authors included complications that affect the clinical outcomes of the surgery, while others reported minor complications that do not affect the clinical outcomes such as minor reversible neurologic deficit or minimal scapular notching. This review article summarizes the processes related to diagnosis and treatment of complications after reverse shoulder arthroplasty with the aim of helping clinicians reduce complications and perform appropriate procedures if/when complications occur.

Preventing brachial plexus injury during shoulder surgery: a real-time cadaveric study

BACKGROUND

Brachial plexopathy is not uncommon after shoulder surgery. Although thought to be due to stretch neuropathy, its etiology is poorly understood. This study aimed to identify arm positions and maneuvers that may risk causing brachial plexopathy during shoulder arthroplasty.

METHODS

Tensions in the cords of the brachial plexuses of 6 human cadaveric upper limbs were measured using load cells while each limb was placed in different arm positions and while they underwent shoulder hemiarthroplasty and revision reverse arthroplasty. Arthroplasty procedures in 4 specimens were performed with standard limb positioning (unsupported), and 2 specimens were supported from under the elbow (supported). Each cord then underwent biomechanical testing to identify tension corresponding to 10% strain (the stretch neuropathy threshold in animal models).

RESULTS

Tensions exceeding 15 N, 11 N, and 9 N in the lateral, medial, and posterior cords, respectively, produced 10% strain. Shoulder abduction >70° and combined external rotation >60° with extension >50° increased medial cord tension above the 10% strain threshold. Medial cord tensions (mean ± standard error of the mean) in unsupported specimens increased over baseline during hemiarthroplasty (sounder insertion [4.7 ± 0.6 N, P = .04], prosthesis impaction [6.1 ± 0.8 N, P = .04], and arthroplasty reduction [5.0 ± 0.7 N, P = .04]) and revision reverse arthroplasty (retractor positioning [7.2 ± 0.8 N, P = .02]). Supported specimens experienced lower tensions than unsupported specimens.

CONCLUSIONS

Shoulder abduction >70°, combined external rotation >60° with extension >50°, and downward forces on the humeral shaft may risk causing brachial plexopathy. Retractor placement, sounder insertion, humeral prosthesis impaction, and arthroplasty reduction increase medial cord tensions during shoulder arthroplasty. Supporting the arm from under the elbow protected the brachial plexus in this cadaveric model.

Neurologic complications of shoulder joint replacement

BACKGROUND

Little attention has been given to neurologic complications after shoulder joint replacement (SJR). Previously thought to occur infrequently, it is likely that many are not clinically recognized, and they can result in postoperative morbidity and impair the patient's recovery. The purpose of this study was to document the prevalence of nerve complications after SJR, to identify the nerves involved, and to define patient outcomes.

METHODS

This was a retrospective review of 211 SJRs in 202 patients during a 5-year period were included, with 89 male and 122 female patients at an average age of 70 years. All patients underwent a comprehensive analysis of any postoperative nerve complication, including onset, duration, investigation, treatment, and symptom resolution.

RESULTS

Of the 211 SJR procedures, 44 were identified as having sustained a nerve complication (20.9%), with 36 female (81.8%) and 8 male patients (18.2%). Reverse SJR was associated with the highest number of nerve complications. The median nerve (25 patients) and musculocutaneous nerve (8 patients) were most commonly involved. Most nerve complications were transient and resolved within 6 months. Permanent sequelae and injuries that required secondary surgical intervention were rare.

CONCLUSION

The occurrence of nerve complications after SJR is common, but almost all will fully recover. Most are transient neurapraxias involving the lateral cord of the brachial plexus. Women are more likely to be affected, as are patients who have undergone prior surgery to the affected shoulder. Most are likely to be the result of excessive traction or direct injury to the nerves during glenoid exposure.

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.

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.

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

OBJECTIVE

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

INDICATIONS

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

CONTRAINDICATIONS

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

SURGICAL TECHNIQUE

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

POSTOPERATIVE TREATMENT

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

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.

Avulsive axillary artery injury in reverse total shoulder arthroplasty

In addition to neurologic injuries such as peripheral nerve palsy, axillary vessel injury should be recognized as a possible complication of reverse total shoulder arthroplasty. Limb lengthening associated with Grammont-type reverse total shoulder arthroplasty places tension across the brachial plexus and axillary vessels and may contribute to observed injuries. The Grammont-type reverse total shoulder arthroplasty prosthesis reverses the shoulder ball and socket, shifts the shoulder center of rotation distal and medial, and lengthens the arm. This alteration of native anatomy converts shearing to compressive glenohumeral joint forces while augmenting and tensioning the deltoid lever arm. Joint stability is enhanced; shoulder elevation is enabled in the rotator cuff–deficient shoulder. Arm lengthening associated with reverse total shoulder arthroplasty places a longitudinal strain on the brachial plexus and axillary vessels. Peripheral nerve palsies and other neurologic complications of reverse total shoulder arthroplasty have been documented. The authors describe a patient with rotator cuff tear arthropathy and a history of radioulnar synostosis who underwent reverse total shoulder arthroplasty complicated by intraoperative injury to the axillary artery and postoperative radial, ulnar, and musculocutaneous nerve palsies. Following a seemingly unremarkable placement of reverse shoulder components, brisk arterial bleeding was encountered while approximating the incised subscapularis tendon in preparation for wound closure. Further exploration revealed an avulsive-type injury of the axillary artery. After an unsuccessful attempt at primary repair, a synthetic arterial bypass graft was placed. Reperfusion of the right upper extremity was achieved and has been maintained to date. Postoperative clinical examination and electromyographic studies confirmed ongoing radial, ulnar, and musculocutaneous neuropathies.

Iatrogenic nerve injuries during shoulder surgery

INTRODUCTION

The current literature indicates that neurologic injuries during shoulder surgery occur infrequently and result in little if any morbidity. The purpose of this study was to review one institution's experience treating patients with iatrogenic nerve injuries after shoulder surgery.

METHODS

A retrospective review of the records of patients evaluated in a brachial plexus specialty clinic from 2000 to 2010 identified twenty-six patients with iatrogenic nerve injury secondary to shoulder surgery. The records were reviewed to determine the operative procedure, time to presentation, findings on physical examination, treatment, and outcome.

RESULTS

The average age was forty-three years (range, seventeen to seventy-two years), and the average delay prior to referral was 5.4 months (range, one to fifteen months). Seven nerve injuries resulted from open procedures done to treat instability; nine, from arthroscopic surgery; four, from total shoulder arthroplasty; and six, from a combined open and arthroscopic operation. The injury occurred at the level of the brachial plexus in thirteen patients and at a terminal nerve branch in thirteen. Fifteen patients (58%) did not recover nerve function after observation and required surgical management. A structural nerve injury (laceration or suture entrapment) occurred in nine patients (35%), including eight of the thirteen who presented with a terminal nerve branch injury and one of the thirteen who presented with an injury at the level of the brachial plexus.

CONCLUSIONS

Nerve injuries occurring during shoulder surgery can produce severe morbidity and may require surgical management. Injuries at the level of a peripheral nerve are more likely to be surgically treatable than injuries of the brachial plexus. A high index of suspicion and early referral and evaluation should be considered when evaluating patients with iatrogenic neurologic deficits after shoulder surgery.

Glenoid screw position in the Encore Reverse Shoulder Prosthesis: an anatomic dissection study of screw relationship to surrounding structures

BACKGROUND

Fixation of the baseplate to the glenoid for the Reverse Shoulder Prosthesis (DJO Surgical, Austin, TX, USA) requires secure screw purchase to avoid excessive micromotion and baseplate failure. The best screw length for fixation is unknown. In addition, excessively long screws or a plunge of the drill bit during baseplate insertion could injure surrounding structures.

METHODS

Reverse Shoulder Prosthesis baseplates were inserted in 10 fresh-frozen shoulders by use of a 6.5-mm central screw and four 5.0-mm peripheral locking screws placed 90° to the baseplate. The top superior screw was placed into the base of the coracoid, corresponding to the 1-o'clock position in a right shoulder. The distances to surrounding vital structures were recorded, screws were removed, and screw hole lengths were measured to determine the most effective lengths in different parts of the glenoid scapula.

RESULTS

The screw length was 30 mm for the superior screw holes, 28 mm for the inferior screw holes, 13 mm for the anterior screw holes, and 15 mm for the posterior screw holes. The central screw trajectory was through the anterior cortex. The anterior screw trajectory violated the subscapularis belly in all specimens. The posterior screw touched the suprascapular nerve or artery in 3 of 10 specimens.

DISCUSSION

The superior and inferior screws have the longest bony fixation. Drill bit plunge during placement of the anterior screw poses a risk to the subscapularis muscle. Drilling for the posterior screw risks injury to the suprascapular nerve and artery at the spinoglenoid notch.

CONCLUSIONS

The posterior screw should be placed with care to avoid neurovascular complications.

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.

Human cadaveric study of subscapularis muscle innervation and guidelines to prevent denervation

The upper and lower subscapular nerves provide innervation to the subscapularis muscle. However, the axillary nerve may provide a significant innervation to the lower portion of the muscle. The prevalence and patterns of anomalous innervation of the subscapularis muscle were studied to determine if these variations increased the risk of muscle denervation during open shoulder surgery. Twenty human cadaveric shoulders were dissected, and the innervation to the subscapularis was defined. The distance from the nerve insertion to the shoulder joint was measured in neutral and maximal external rotation. In the most common variation, the lower subscapular nerve arose from the axillary nerve (5 specimens; 25%). Although external rotation of the shoulder brought the nerve insertion significantly more lateral (35.2 to 16.9 mm, P < .001), the origin of the nerve had no significant effect on nerve proximity to the joint. The closeness of the nerve insertions to the shoulder joint warrants care during an anterior approach to the shoulder and dissections on the anterior surface of the muscle. Subscapularis nerve damage or denervation may cause unexplained joint instability and subscapularis dysfunction.

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.

[Contribution to subscapularis nerve supply. 18 dissections]

INTRODUCTION

Dividing the subscapularis muscle along its fibers axis allows approaching the glenohumeral joint. The more medial its division, the more possible injury of its nerve supply.

AIM

The aim of our study was to assess the subscapularis nerve supply through cartography of the entry points of subscapularis nerves from simple landmarks, reproducible by triangulation.

MATERIAL AND METHODS

On 18 formalin-preserved shoulders, after dissection of the subscapularis nerves, distances were measured between entry points of subscapularis nerves and the following landmarks: center of the minor tubercle (tm), upper and lower poles of the glenoid cavity (cgs and cgi), apex of the coracoid process (pc).

RESULTS

There were in average 3.33 subscapularis nerves (2-4). These different nerves split most often before entering subscapularis muscle; there were in average 5.05 entry points (3-6). Distances between entry points and clinical landmarks were as follows: cgs, 3.9-6.45 cm; cgi, 3.7-5.54 cm; tm, 5.9-7.15 cm; pc, 4.9-7.66 cm. Reporting these measurements onto a frame allowed to show that all these points were located in average medially to the scapular notch and at more than 3 cm from the anterior border of the glenoid cavity.

CONCLUSION

If the transverse division does not extend farther than 3 cm from the anterior border of the glenoid cavity and from the medial border of the root of the coracoid process, there should not be any injury of the subscapularis nerves.

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

The axillary nerve has long been known to be one of the nerves vulnerable to damage during shoulder arthroscopic and open surgical procedures. The relationship of the axillary nerve to the shoulder capsule and the subscapularis muscle has not been well defined in orthopedic literature. This descriptive anatomical study aimed to present the course and the relations of the axillary nerve with neighboring neurovascular structures and the shoulder capsule and to define anatomical landmarks and regions that can be used practically in anterior surgical approaches to the shoulder region. To investigate the course of the axillary nerve and its relationship with neighboring structures, 30 shoulders of 15 fixed adult cadavers were dissected under the microscope through an anterior approach. A triangle-shaped anatomic area containing the axillary neurovascular bundle was defined. The closest distance between the axillary nerve and the anteromedial aspect of the coracoid tip and the glenoid labrum was measured as 3.7 cm and 1.1 cm on average, respectively. The distance between the anteromedial aspect of the coracoid tip and the point where the nerve passes through the medial edge of the subscapularis was measured as 2.5 cm on average. The results of this study demonstrate the anatomic pattern and the course of the axillary nerve and its relations with the shoulder capsule. Knowing the exact localization of the axillary nerve under the guidance of the defined anatomic triangle may provide a safer surgery.

Innervation patterns of the inferior glenohumeral ligament: Anatomical and biomechanical relevance

Although the Inferior Glenohumeral Ligament (IGHL) has a well known mechanical and proprioceptive relevance in shoulder stability, the interrelation of the ligament's anatomical disposition/innervation has not actually been described previously. The purpose of the study was to determine the IGHL innervation patterns and relate them to dislocation. Forty-five embalmed and 16 fresh-frozen human cadaveric shoulders were studied. Masson's Trichrome staining detailed the intraligamentous nerve fiber arrangements. The effect on the articular nerves of an anteroinferior dislocation of the shoulder joint and the position of 60 degrees abduction and 45 degrees external rotation was studied dynamically. The axillary nerve provided IGHL innervation in 95.08% of the cases. We saw two distinct innervation patterns originating from the axillary nerve. In Type 1, one or two collaterals diverged later from the main trunk to enter the ligament. Type 2 showed innervation to the ligament provided by the posterior branch for three to four neural branches. In both cases, these branches enter the ligament near the glenoid rim and at the 7 o'clock position (right shoulder). The radial nerve (Type 3 innervation pattern) provided IGHL innervation in 3.28% of the cases. Microscopic analysis revealed wavy intraligamentous neural branches. The articular branches relaxed and separated from the capsule at the apprehension position and stayed intact after dislocation. These results showed a special predisposition to avoid possible denervation and suggested that the neural arch probably remains unaffected after most dislocations. Knowledge of the neural anatomy of the shoulder will clearly help in avoiding its injury in surgical procedures.

Postoperative shoulder rehabilitation

This article focuses on the rehabilitation considerations for several shoulder surgeries: acromioplasty, rotator cuff repair, rotator cuff debridement, Bankart repair, thermal capsulorrhaphy, superior labral anterior posterior repair, multidirectional instability, proximal humerus fracture, surgical management of the stiff shoulder, arthroplasty,and fusion. General guidelines are presented for discussing and planning rehabilitation for patients, including exercises, timing of progression, patient education, precautions or restrictions, and expectations.