Quadrilateral space syndrome: diagnosis and operative decompression technique

A Surgical Framework for the Management of Incomplete Axillary Nerve Injuries

BACKGROUND

 Axillary nerve injury is the most common nerve injury affecting shoulder function. Nerve repair, grafting, and/or end-to-end nerve transfers are used to reconstruct complete neurotmetic axillary nerve injuries. While many incomplete axillary nerve injuries self-resolve, axonotmetic injuries are unpredictable, and incomplete recovery occurs. Similarly, recovery may be further inhibited by superimposed compression neuropathy at the quadrangular space. The current framework for managing incomplete axillary injuries typically does not include surgery.

METHODS

 This study is a retrospective analysis of 23 consecutive patients with incomplete axillary nerve palsy who underwent quadrangular space decompression with additional selective medial triceps to axillary end-to-side nerve transfers in 7 patients between 2015 and 2019. Primary outcome variables included the proportion of patients with shoulder abduction M3 or greater as measured on the Medical Research Council (MRC) scale, and shoulder pain measured on a Visual Analogue Scale (VAS). Secondary outcome variables included pre- and postoperative Disabilities of the Arm, Shoulder, and Hand Questionnaire (DASH) scores.

RESULTS

 A total of 23 patients met the inclusion criteria and underwent nerve surgery a mean 10.7 months after injury. Nineteen (83%) patients achieved MRC grade 3 shoulder abduction or greater after intervention, compared with only 4 (17%) patients preoperatively (p = 0.001). There was a significant decrease in VAS shoulder pain scores of 4.2 ± 2.5 preoperatively to 1.9 ± 2.4 postoperatively (p < 0.001). The DASH scores also decreased significantly from 48.8 ± 19.0 preoperatively to 30.7 ± 20.4 postoperatively (p < 0.001). Total follow-up was 17.3 ± 4.3 months.

CONCLUSION

 A surgical framework is presented for the appropriate diagnosis and surgical management of incomplete axillary nerve injury. Quadrangular space decompression with or without selective medial triceps to axillary end-to-side nerve transfers is associated with improvement in shoulder abduction strength, pain, and DASH scores in patients with incomplete axillary nerve palsy.

Quadrangular Space Syndrome: a systematic review of surgical and medical therapeutic advances

Background

The axillary nerve and posterior circumflex humeral artery are compressed in Quadrangular Space Syndrome (QSS), which can be treated with conservative approaches or surgical decompression in recalcitrant instances. There are no clear guidelines for determining which surgical method is optimal for treating QSS and other disorders that mirror QSS.

Objective

The goal of this study is to grade and review past, current, and planned medicinal and surgical care modalities for QSS.

Materials and Methods

The review protocol is registered with PROSPERO (ID: CRD42022332766). To identify recent advances in the methods/techniques of medical and surgical management of QSS, PubMed and Medline databases were searched until March 2022 for publications, including case studies, case reports, and review articles, using medical subject headings terms like quadrilateral space syndrome, surgical management, and medical management. Throughout the study, all the authors scrupulously followed a well-developed registered review process and the risk of bias in systematic reviews guidance tool. Data on proposed medical and surgical management methods/techniques were compiled, and each was analyzed based on the underlying neuro-vascular systems.

Results

There were 88 items found in the first search. Following applying the inclusion and exclusion criteria, 16 papers were chosen for synthesis in the review study after a thorough assessment. Three studies (conservative and advanced) focused on medical care of QSS, while 12 articles (prior, current, and newer) focused on surgical management of QSS. Only four of the 15 studies reviewed proposed different surgical approaches/techniques for surgical decompression in QSS.

Conclusions

There were two regularly used surgical procedures discovered, one anterior/delto-pectoral and the other posterior/ scapular. The anterior route is more technically straightforward and can be employed for surgical QSS decompression.

Revisiting the Surgical Approaches to Decompression in Quadrilateral Space Syndrome: A Cadaveric Study

Background

Quadrangular space syndrome involves compression of the axillary nerve and posterior circumflex humeral artery. In a few cases, its management requires surgical decompression. The current study reviews the surgical approaches used in the decompression of neurovascular structures and presents our reflections and recommendations.

Methodology

In this study, four human cadavers were used for dissection of the axillae and the scapular region by the senior residents of the Department of Anatomy and Department of Orthopedics. The residents dissected the quadrangular space in the eight upper limbs using anterior and posterior surgical approaches.

Results

To identify the quadrangular space and secure its contents, the posterior approach was recognized as the easier and quicker method by both Anatomy and Orthopedic residents; however, it may result in increased postoperative morbidity. Although the anterior (deltopectoral) approach involves more skill, it reduces postoperative morbidity.

Conclusions

The anterior (deltopectoral) approach with suggested modifications can be an effective method in the surgical decompression of quadrangular space syndrome. The authors suggest more cadaveric studies to provide anatomists and surgeons with the opportunity to practice and evaluate older and newer surgical approaches.

A Review of Upper Extremity Peripheral Nerve Injuries in Throwing Athletes

Peripheral nerve injuries in the upper extremities may be common in throwing athletes as the throwing motion places extreme stress on the dominant arm. The combination of extreme stress along with repetitive microtrauma from throwing uniquely places the throwing athlete at elevated risk of upper extremity peripheral nerve injury. However, because symptoms can be non-specific and frequent co-exist with pathology in the upper extremity, the diagnosis of peripheral nerve injury is often delayed. Diagnosis of peripheral nerve injuries may require a combination of history and physical exam, diagnostic imaging, electrodiagnostic testing, and diagnostic ultrasound guided injections. The primary management should include physical therapy focusing on throwing mechanics and kinetic chain evaluation. However, some athletes require surgical intervention if symptoms do not improve with conservative management. The purpose of this focused narrative review is to highlight upper extremity peripheral neuropathies reported in throwing athletes and to provide an overview of the appropriate clinical diagnosis and management of the throwing athlete with a peripheral nerve injury. This article is protected by copyright. All rights reserved.

Quadrilateral space syndrome induced by a large degenerative osteophyte

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

Nerve Compression Syndromes of the Shoulder

Nerve compression syndromes of the shoulder contribute to pain, paresthesia, and weakness of the upper extremity. This review examines the recent literature regarding thoracic outlet syndrome, suprascapular neuropathy, long thoracic nerve palsy, and quadrilateral space syndrome. Overlapping features are common among shoulder pathologies, and thus, key anatomical features, pathophysiology, clinical manifestations, diagnostic techniques, and treatments are highlighted for all aforementioned conditions.

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

INTRODUCTION

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

HYPOTHESIS

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

MATERIAL AND METHODS

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

RESULTS

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

DISCUSSION

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

CONCLUSION

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

LEVEL OF EVIDENCE

IV.

Quadrilateral space syndrome: a review

Quadrilateral space (QS) syndrome (QSS) is a relatively rare condition in which the axillary nerve and the posterior humeral circumflex artery are compressed within the QS. Fibrous bands are most commonly implicated as the cause, with true space-occupying lesions being less common. QSS is characterized by poorly localized shoulder pain and paresthesia over the lateral aspect of the shoulder and arm in a nondermatomal pattern. These symptoms are aggravated by shoulder abduction and external rotation. Point tenderness is typically present over the QS; however, diagnosis on physical examination can be difficult. Pain relief after lidocaine block of the axillary nerve within the QS is a useful finding in the evaluation of patients with suspected QSS. No definitive diagnostic imaging exists, making diagnosis difficult, although radiographs and magnetic resonance imaging are recommended to rule out other pathology. Nonoperative treatment, including nonsteroidal anti-inflammatory drugs, activity modification, and physical therapy, for at least 6 months is recommended before pursuing operative intervention. Small case series have shown that surgical decompression of the QS has good outcomes, with resolution of pain and return to sport.

Quadrilateral Space Syndrome: Diagnosis and Clinical Management

Quadrilateral space syndrome (QSS) is a rare disorder characterized by axillary nerve and posterior humeral circumflex artery (PHCA) compression within the quadrilateral space. Impingement is most frequently due to trauma, fibrous bands, or hypertrophy of one of the muscular borders. Diagnosis can be complicated by the presence of concurrent traumatic injuries, particularly in athletes. Since many other conditions can mimic QSS, it is often a diagnosis of exclusion. Conservative treatment is often first trialed, including physical exercise modification, physical therapy, and therapeutic massage. In patients unrelieved by conservative measures, surgical decompression of the quadrilateral space may be indicated.

Clinical outcomes after decompression of the nerve to the teres minor in patients with idiopathic isolated teres minor fatty atrophy

BACKGROUND

The purpose of this manuscript is to describe what we believe to be the first series of patients surgically treated for idiopathic isolated teres minor atrophy and to present the results of surgical decompression of the nerve to the teres minor.

METHODS

This is a retrospective cohort of 22 patients who underwent decompression of the nerve to the teres minor for isolated teres minor atrophy. Clinical data including duration of symptoms, additional diagnoses, concurrent procedures, preoperative physical examination findings, imaging data, and preoperative visual analog scale (VAS), Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons (ASES) scores were collected from the medical record. Postoperative patient-based clinical outcome measures including VAS, SST, and ASES scores were obtained during clinical examination or by telephone interview.

RESULTS

Average length of follow-up was 26 months. Nine patients had concurrent procedures performed. Preoperatively, 12 of 14 (86%) had external rotation weakness in Hornblower's position. Postoperatively, pain scores decreased an average of 4 points; ASES scores increased 31.7 ± 20.2 points; SST scores increased 3.1 ± 2.3 points. No external rotation weakness was noted postoperatively in any tested patient. Two patients developed adhesive capsulitis. No other complications occurred.

CONCLUSIONS

Isolated compression of the nerve to the teres minor is a rare and novel clinical entity. In properly selected cases, open release of the fascial sling enveloping the nerve branches to the teres minor can provide relief of symptoms and clinical improvement.

Quadrilateral space syndrome: the Mayo Clinic experience with a new classification system and case series

Quadrilateral space syndrome (QSS) arises from compression or mechanical injury to the axillary nerve or the posterior circumflex humeral artery (PCHA) as they pass through the quadrilateral space (QS). Quadrilateral space syndrome is an uncommon cause of paresthesia and an underdiagnosed cause of digital ischemia in overhead athletes. Quadrilateral space syndrome can present with neurogenic symptoms (pain and weakness) secondary to axillary nerve compression. In addition, repeated abduction and external rotation of the arm is felt to lead to injury of the PCHA within the QSS. This often results in PCHA thrombosis and aneurysm formation, with distal emboli. Because of relative infrequency, QSS is rarely diagnosed on evaluation of athletes with such symptoms. We report on 9 patients who presented at Mayo Clinic with QSS. Differential diagnosis, a new classification system, and the management of QSS are discussed, with a comprehensive literature review. The following search terms were used on PubMed: axillary nerve, posterior circumflex humeral artery, quadrilateral space, and quadrangular space. Articles were selected if they described patients with symptoms from axillary nerve entrapment or PCHA thrombosis, or if related screening or imaging methods were assessed. References available within the obtained articles were also pursued. There was no date or language restriction for article inclusion; 5 studies in languages besides English were reported in German, French, Spanish, Turkish, and Chinese.

[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.

Neuromuscular ultrasound application to the electrodiagnostic evaluation of quadrilateral space syndrome

Quadrilateral space syndrome (QSS) is a rare neurovascular compression syndrome that results from the compression of the axillary nerve and posterior circumflex humeral artery in the quadrilateral space. Electromyography often is used to evaluate for the presence of neuropathic changes in the deltoid and teres minor in cases of suspected QSS. Needle examination of the teres minor may be challenging because of the muscle's small size and proximity to the infraspinatus. In cases in which patients are overweight or have significant teres minor atrophy, localization of the muscle through conventional methods may be extremely difficult. We present a case of an overweight man with posterior shoulder pain who was diagnosed with QSS via the use of a combination of ultrasound and electromyography.

Teres minor muscle and related anatomy

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Shoulder pain in the overhead throwing athlete

Treatment of the overhead throwing athlete is among the more challenging aspects of orthopaedic sports medicine. Awareness and understanding of the throwing motion and the supraphysiologic forces to which the structures of the shoulder are subjected are essential to diagnosis and treatment. Pain and dysfunction in the throwing shoulder may be attributed to numerous etiologies, including scapular dysfunction, intrinsic glenohumeral pathology (capsulolabral structures), extrinsic musculature (rotator cuff), or neurovascular structures. Attention to throwing mechanics and appropriate stretching, strength, and conditioning programs may reduce the risk of injury in this highly demanding activity. Early discovery of symptoms, followed by conservative management with rest and rehabilitation with special attention to retraining mechanics may mitigate the need for surgical intervention. Prevention of injury is always more beneficial to the long-term health of the thrower than is surgical repair. An anatomic approach is used in this report, focusing on common etiologies of pain in the overhead thrower and emphasizing the clinical presentation and treatment.

Diagnostic pitfalls in spine surgery: masqueraders of surgical spine disease

Disorders of the spine are common in clinical medicine, and spine surgery is being performed with increasing frequency in the US. Although many patients with an established diagnosis of a true surgically treatable lesion are referred to a neurosurgeon, the evaluation of patients with spinal disorders can be complex and fraught with diagnostic pitfalls. While “common conditions are common,” astute clinical acumen and vigilance are necessary to identify lesions that masquerade as surgically treatable spine disease that can lead to erroneous diagnosis and treatment. In this review, the authors discuss musculoskeletal, peripheral nerve, metabolic, infectious, inflammatory, and vascular conditions that mimic the syndromes produced by surgical lesions. It is possible that nonsurgical and surgical conditions coexist at times, complicating treatment plans and natural histories. Awareness of these diagnoses can help reduce diagnostic error, thereby avoiding the morbidity and expense associated with an unnecessary operation.

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

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

Surgical decompression of the quadrilateral space in overhead athletes

BACKGROUND

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

HYPOTHESIS

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

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

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

RESULTS

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

CONCLUSION

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

The anatomy of the quadrilateral space with reference to quadrilateral space syndrome

Quadrilateral space syndrome is a rare condition in which the contents of the quadrilateral space, the axillary nerve and the posterior circumflex humeral artery, are compressed, leading to vague symptoms of shoulder pain, tenderness over the quadrilateral space on palpation, and teres minor and deltoid denervation. Fibrous bands within the quadrilateral space are often cited in the literature as a cause of compression in quadrilateral space syndrome; however, Cahill and Palmer did not see these bands in cadaveric dissection. These are postulated to cause compression of the quadrilateral space contents in abduction and external rotation of the shoulder. To clarify the anatomic features that may predispose the development of quadrilateral space syndrome, 16 cadaveric shoulders were studied. Dissection revealed that fibrous bands are a common finding in the quadrilateral space, being present in 14 of 16 shoulders. The most common site for a fibrous band was between the teres major and the long head of the triceps. Where the bands were present, both internal and external rotation of the shoulder caused a reduction in the cross-sectional area of the quadrilateral space.

An unusual cause of the quadrilateral space impingement syndrome by a bone spike

The quadrilateral space impingement syndrome is a clinical syndrome resulting from compression of the axillary nerve and the posterior circumflex humeral artery, with subsequent focal atrophy of the teres minor, with or without involvement of portions of the deltoid muscle. This entity has many etiologies. We are reporting a case of this syndrome caused by a bone spike from a malunited old scapular fracture following a motor vehicle accident. The bone spike impinged on the axillary nerve as it passes through the quadrilateral space, causing focal atrophy of the teres minor muscle. The abnormality was well demonstrated by MD-CT.

The anatomic branch pattern of the axillary nerve

The purpose of this study is to determine the surgical anatomy and innervation pattern of the branches of the axillary nerve and discuss the clinical importance of the presented findings. We dissected 30 shoulders in 15 fixed adult cadavers under a microscope through anterior and posterior approaches. The axillary nerve was examined in 2 segments in relation to the underlying subscapularis muscle. The axillary nerve gave off no branches in the first segment in 85% of cases. When the posterior approach was used, the axillary nerve and its branches were observed to be in a triangular-shaped area. The mean distance from the posterolateral corner of the acromion to the axillary nerve and its branches was 7.8 cm. In all cases, the posterior branch of the axillary nerve gave off its first muscular branch to innervate the teres minor. The joint branch of the axillary nerve was observed to branch out in 3 different patterns. The acromial and clavicular parts of the deltoid muscle were observed to be innervated from the anterior branch of the axillary nerve in all cases. The posterior part of the deltoid muscle was observed to be innervated in 3 different patterns. The posterior part of the deltoid was innervated from the branch or branches coming only from the posterior branch in 70% of cases, from the anterior and posterior branches in 26.7% of cases, and from the anterior branch in 3.3% of cases. The findings of this study are useful for identifying each of the branches of the axillary nerve and have implications for surgeries related with selective innervation.

Hourglass-like constriction of the axillary nerve: report of two patients

Among the various etiologies of compressive lesions, the development of an hourglass-like constriction of the nerve that is unrelated to any recognizably compressive structure is a very rare phenomenon. This problem has been reported previously for the radial nerve and its branch posterior interosseous nerve and for the anterior interosseous nerve, a branch of median nerve. Here we report 2 cases of hourglass-like constriction of the axillary nerve that were observed during surgery; the constrictive segment was unrelated to any compressive structure.

Quadrilateral space syndrome caused by a humeral osteochondroma: a case report and review of literature

Quadrilateral space syndrome (QSS) is a rare condition in which the posterior humeral circumflex artery and the axillary nerve are entrapped within the quadrilateral space. The main causes of the entrapment are abnormal fibrous bands and hypertrophy of the muscular boundaries. Many other space-occupying causes such as a glenoidal labral cyst or fracture hematoma have been reported in the literature. However, we could not find a report on classical QSS caused by an osteochondroma. The aim of this case report is to attract attention to an unusual etiology of shoulder pain, and to emphasize the importance of physical examination and x-ray imaging before performing more complex attempts for differential diagnosing.

Surgical anatomy of the axillary nerve within the quadrangular space

Object. There is a paucity of literature regarding the surgical anatomy of the quadrangular space (QS), which is a potential site of entrapment for the axillary nerve. Muscle hypertrophy of this geometrical area and fascial bands within it have been implicated in compression of the axillary nerve.

Methods. Fifteen human cadavers (30 sides) were dissected for this study. Measurements of the QS and its contents were made. The mean height of this space was 2.5 cm and the mean width 2.5 cm; its mean depth was 1.5 cm. The axillary nerve was always the most superior structure in the space, and in all cases the nerve and artery hugged the surgical neck of the humerus just superior to the origin of the lateral head of the triceps brachii muscle. This arrangement placed the axillary nerve in the upper lateral portion of the QS in all cadaveric specimens. The nerve branched into its muscular components within this space in 10 sides (33%) and posterior to it in 20 sides (66%). The cutaneous component of the axillary nerve branched from the main trunk of the nerve posterior to the QS in all specimens. Fascial bands were found in this space in 27 (90%) of 30 sides.

Conclusions. Knowledge of the anatomy of the QS may aid the surgeon who wishes to explore and decompress the axillary nerve within this geometrical confine.

Value of Magnetic Resonance Imaging for Muscle Denervation Syndromes of the Shoulder Girdle

Clinical evaluation of neuromuscular disorders typically consists of obtaining a detailed clinical history, physical examination, and electrophysiologic examinations. Electrodiagnostic examinations significantly aid in distinguishing between myopathy, neuropathy, and neuromuscular disorders. Electrodiagnostic examinations also assist in determining the severity and extent of disease. Progress can also be monitored on follow-up testing. The benefit of magnetic resonance imaging (MRI) in neuromuscular disease evaluation lies primarily in identifying a specific underlying gross pathologic cause and its location in the neuraxis as well as in identifying associated secondary findings. In some cases, MRI is particularly helpful when a solitary, small, deep muscle is affected. Imaging can be useful in assessing clinical progress in some cases. Causes of muscle denervation include mass lesions and trauma as well as infectious, autoimmune, and idiopathic causes. This article illustrates the common denervation syndromes that involve the shoulder girdle: Parsonage-Turner syndrome, quadrilateral space syndrome, and suprascapular neuropathy. By demonstrating the exact muscles involved and spared, MRI noninvasively identifies the level of nerve insult in the neuraxis. Furthermore, in cases in which a mass is responsible for denervation, MRI can directly show the cause and aid in treatment planning.

Quadrilateral Space Syndrome: Incidence of Imaging Findings in a Population Referred for MRI of the Shoulder

OBJECTIVE

The purpose of this study was to determine the incidence of MRI findings suggesting quadrilateral space syndrome in a population referred for shoulder MRI.

CONCLUSION

Focal teres minor atrophy or abnormal signal suggesting quadrilateral space syndrome is an uncommon, although not rare, finding on MRI of the shoulder in our referral population and is rarely an isolated abnormality.

Nerve injury about the shoulder in athletes, part 1: suprascapular nerve and axillary nerve

Nerve injuries about the shoulder in athletes are being recognized with increasing frequency. Prompt and correct diagnosis of these injuries is important to treat the patient and to understand the potential complications and natural history so as to appropriately counsel athletes. This 2-part article is a review and an overview of the current state of knowledge regarding some of the more common nerve injuries seen about the shoulder in athletes.

Occupational and Sport Related Traumatic Neuropathy

BACKGROUND

Sport and occupation related traumatic nerve injury is a common problem in the United States. While the physical requirements of each pursuit place participants at risk for injury to certain peripheral nervous system structures, the vast numbers of professional and recreational pursuits limits the ability to become familiar with nerve injuries specific to each. A more pragmatic approach is to apply knowledge of mechanisms of injury, physiology of nerve injury, regional anatomy, and at-risk peripheral nervous system structures to the routine neurologic history and physical assessment to arrive at a localizing and etiologic diagnosis.

REVIEW SUMMARY

The authors discuss potential mechanisms of nerve injury, the role of electrodiagnostic testing, regional peripheral nervous system anatomic considerations and lesion localization.

CONCLUSIONS

Despite the wide variety of professionally and recreationally induced peripheral nerve injuries, application of anatomic, physiologic and mechanistic considerations allow the neurologist to make an etiologic and localizing diagnosis.

The posterior branch of the axillary nerve: an anatomic study

BACKGROUND

Surgery on the posterior aspect of the shoulder has become accepted practice for a number of pathological conditions affecting the scapula and the glenohumeral joint. Despite this trend, the anatomy of the posterior branch of the axillary nerve has not been well characterized. The purpose of the present study was to determine the innervation pattern and surgical relationships of the posterior branch of the axillary nerve.

METHODS

Nineteen fresh-frozen human cadaveric forequarter amputation specimens were dissected through a posterior approach. The location of the posterior branch of the axillary nerve and its anatomical relationships with surrounding structures were documented and measured with use of digital calipers.

RESULTS

The posterior branch separated from the main anterior circumflex branch of the axillary nerve immediately anterior to the origin of the long head of the triceps muscle at the six o'clock position on the glenoid. It coursed posteriorly, adjacent to the inferior aspect of the glenoid rim for an average distance of 10 mm (range, 2 to 17 mm) before dividing into the superior-lateral brachial cutaneous nerve and the nerve to the teres minor. The nerve to the teres minor coursed medially along the posterior aspect of the inferior part of the glenoid rim for an average distance of 18 mm (range, 11 to 25 mm) before entering the muscle at its inferior border. The superior-lateral brachial cutaneous nerve coursed inferiorly, deep to the posterior aspect of the deltoid. It became superficial by passing around the medial border of the muscle at an average of 8.7 cm (range, 6.3 to 10.9 cm) inferior to the posterolateral corner of the acromion.

CONCLUSIONS

The posterior branch of the axillary nerve has an intimate association with the inferior aspects of the glenoid and shoulder joint capsule, which may place it at particular risk during capsular plication or thermal shrinkage procedures. The superior-lateral brachial cutaneous nerve and the nerve to the teres minor always arise from the posterior branch. Thus, loss of sensation over the deltoid may indicate loss of teres minor function. The posterior aspect of the deltoid has a more consistent supply from the anterior branch of the axillary nerve, necessitating caution when performing a posterior deltoid-splitting approach to the shoulder.

Compressive neuropathies of the upper extremity

Although any peripheral nerve may be compressed anywhere along its course, nerve compression syndromes typically occur at predictable sites with predictable clinical presentations. A detailed history and physical examination can establish a diagnosis, and electrodiagnostic studies and at times imaging can confirm it. Physicians should adopt a systematic approach of diagnosing and treating these types of nerve lesions. The physician and the patient can be rewarded with favorable outcomes.

Axillary nerve injury: diagnosis and treatment

Axillary nerve injury is infrequently diagnosed but is not a rare occurrence. Injury to the nerve may result from a traction force or blunt trauma applied to the shoulder. The most common zone of injury is just proximal to the quadrilateral space. Atraumatic causes of neuropathy include brachial neuritis and quadrilateral space syndrome. The vast majority of patients recover with non-operative treatment. Baseline electromyographic and nerve conduction studies should be obtained within 4 weeks after injury, with a follow-up evaluation at 12 weeks. If no clinical or electromyographic improvement is noted, surgery may be appropriate. The results of operative repair are best if surgery is performed within 3 to 6 months from the injury. Surgical options include neurolysis, nerve grafting, and neurotization. The results of repair of axillary nerve injuries have been good compared with treatment of other peripheral nerve lesions, due to the monofascicular composition of the nerve and the relatively short distance between the zone of injury and the motor end-plate.

Quadrilateral space syndrome: case report and review of the literature

The quadrilateral space syndrome is defined as tenderness over the quadrilateral space and shoulder pain radiating to the arm, secondary to compression of the axillary nerve and posterior circumflex humeral artery in the quadrilateral space. The symptoms are aggravated by forced abduction and extrenal rotation of the arm. The diagnosis is clinical and is documented by arteriography or angio-MR imaging with dynamic maneuvers. A 30-year-old woman presenting with this syndrome is described here, the differential diagnosis discussed, and the literature reviewed.

Injuries to the shoulder in the throwing athlete. Part two: evaluation/treatment

In part one of this three-part series (March/April 2000), I concentrated on summarizing the biomechanics of the normal throwing shoulder and the pathophysiology of injury. A classification of injury was presented that was based on the principles contained in that article. Part two of this series will focus on the evaluation and treatment of injuries, expanded from an understanding of the principles learned in part one. The ability to perform a skillful examination, and thus develop an accurate diagnosis, is the foundation for treatment. Fortunately, many difficulties encountered in a thrower's shoulder can be treated with a nonoperative approach. However, in instances where conservative measures fail, an improved understanding of the pathophysiology of injury and the development of improved surgical techniques are leading to more accurate diagnoses and more successful rates of return of the athlete to a premorbid level of activity.

Uncommon nerve compression syndromes of the upper extremity

Nerve compression syndromes are a common cause of pain, sensory disturbance, and motor weakness in both the upper and the lower extremities. Although carpal tunnel syndrome is frequently diagnosed and treated surgically with success, other compression syndromes are less common and are often best treated nonsurgically. Understanding the anatomy of the major peripheral nerves with respect to intermuscular septa, fibrous bands, muscle margins, and internervous planes is crucial to understanding how and where peripheral nerve compression can occur. Some conditions, such as anterior interosseous nerve syndrome, respond well to nonoperative treatment; others, such as posterior interosseous nerve syndrome, are better treated by surgical intervention. The authors discuss the anatomic and pathologic causes for compression syndromes, as well as guidelines for treatment and outcomes.

Axillary neuropathy in volleyball players: report of two cases and literature review

Two cases of isolated neuropathy, not consequent to acute trauma, of the axillary nerve of young volleyball players are described. Interest in the pathology derives from the rarity of such case reports and the fact that the pathogenesis may be linked to a specific sporting activity. The lesion site is thought to be in the quadrilateral space.

The quadrilateral space syndrome

We describe a 21-year-old woman with left shoulder pain increased by desk work. Left subclavian angiography disclosed occlusion of the posterior circumflex humeral artery on abduction and external rotation of the arm, compatible with the previous reports of the quadrilateral space syndrome. This syndrome should be considered in patients with shoulder pain of unknown aetiology.