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

Upper-limb neurovascular compression, pectoralis minor and quadrilateral space syndromes: A narrative review of current literature

Pectoralis minor syndrome (PMS) and quadrilateral space syndrome (QSS) are uncommon neurovascular compression disorders affecting the upper extremity. PMS involves compression under the pectoralis minor muscle, and QSS results from compression in the quadrilateral space-both are classically observed in overhead-motion athletes. Diagnosing PMS and QSS may be challenging due to variable presentations and similarities with other, more common, upper-limb pathologies. Although there is no gold standard diagnostic, local analgesic muscle-block response in a patient with the appropriate clinical context is often all that is required for an accurate diagnosis after excluding more common etiologies. Treatment ranges from conservative physical therapy to decompressive surgery, which is reserved for refractory cases or severe, acute vascular presentations. Decompression generally yields favorable outcomes, with most patients experiencing significant relief and restored baseline function. In conclusion, PMS and QSS, although rare, can cause debilitating upper-extremity symptoms; accurate diagnosis and appropriate treatment offer excellent outcomes, alleviating pain and disability.

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 subscapularis muscle: A meta-analysis of its variations, prevalence, and anatomy

BACKGROUND

The subscapularis (SSC) is the largest rotator cuff muscle and is involved in the medial rotation, abduction, adduction, and anterior stabilization of the shoulder. It is anatomically variable, as is the morphology and prevalence of the accessory SSC (aSSC), a rare muscle slip attached to the SSC. There is no current review investigating the prevalence and morphometrics of the SSC and aSSC.

PURPOSE

To investigate the prevalence of the morphological variants of the SSC and aSSC via meta-analysis and review the relevant literature involving cadaveric, magnetic resonance imaging, and ultrasonographic studies.

STUDY DESIGN

Meta-analysis.

MATERIALS AND METHODS

Literature data reporting the prevalence rates and morphometrics of the SSC and aSSC and their variants were pooled. Literature searches and data analyses were performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Anatomical Quality Assurance guidelines.

RESULTS

Forty-six studies, totaling 2166 shoulders, were assessed. The SSC showed an overall length, thickness, cross-sectional area, and volume of 152.2 mm (95% confidence interval, CI, 103.8-200.5 mm), 5.6 mm (95% CI, 4.6-6.6 mm), 18.1 cm² (95% CI, 14.2-22.0 cm² ), and 126.9 cm³ (95% CI, 87.2-166.5 cm³ ), respectively. The SSC displayed substantial variations in its origin and insertion points and in the composition of its tendon. The aSSC had an overall pooled prevalence of 24.6% (95% CI, 0.0%-76.9%).

CONCLUSIONS

The SSC and aSSC have been implicated in multiple shoulder pathologies, including muscle and tendon ruptures and neurovascular compromise. A better understanding of SSC and aSSC variants when diagnosing and treating their related pathologies will reduce patient morbidity and improve treatment regimens.

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.

The proximal humeral attachment of the lateral head of the triceps brachii: a cadaveric study and potential site for radial nerve compression

BACKGROUND

Knowledge of potential compression sites of peripheral nerves is important to the clinician and surgeon alike. One anatomical location for potential compression of the radial nerve, which is rarely mentioned in the literature, is at the proximal humeral attachment of the lateral head of the triceps brachii at the level of the proximal spiral groove. As no anatomical studies have been devoted to this band, the present study was conducted.

METHODS

Ten adult fresh-frozen cadavers were dissected and the lateral head's attachment onto the posterior humerus evaluated for a band. This anatomy and its relation to the radial nerve during range of motion of the elbow and forearm were evaluated.

RESULTS

A band was found on 15 of 20 arms. On five sides, the band was comprised of grossly muscle fibers of the lateral head of the triceps brachii and was not tendinous. The bands were crescent-shaped, straight, and duplicated on nine, five, and one arm, respectively. The length of the bands ranged from 1.1 to 2.2 cm (mean 1.54 cm). The width of the bands ranged from 0.5 to 1.1 cm (mean 0.8 cm). With elbow extension and the forearm in neutral, all bands were lax. With elbow extension and the forearm supinated, the bands became tauter less the muscular bands. In elbow extension and with the forearm in supination, the bands became most taut less the muscular bands.

CONCLUSIONS

The presence of a fibrous band extending from the lateral head of the triceps brachii is common and should be among the differential diagnoses of anatomical sites for potential proximal radial nerve compression when other more common locations are ruled out.

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.

How common is fatty infiltration of the teres minor in patients with shoulder pain? A review of 7,367 consecutive MRI scans

Purpose

The teres minor is particularly important for activities that require external rotation in abduction in the settings of both rotator cuff tears and reverse shoulder arthroplasty. This study sought to assess the incidence of teres minor fatty infiltration in a large cohort of consecutive patients evaluated with shoulder MRI for shoulder pain and to identify all associated pathologies in an effort to determine the various potential etiologies of teres minor involvement.

Methods

A retrospective review of 7,376 non-contrast shoulder MRI studies performed between 2010 and 2015 were specifically evaluated for teres minor fatty infiltration. Studies were reviewed by two fellowship trained musculoskeletal radiologists. Muscle atrophy was graded on a 3-point scale according to Fuchs and Gerber. The remaining rotator cuff tendons and muscles, biceps tendon, labrum, and joint surfaces were assessed on MRI as well.

Results

In this series, 209 (2.8%) shoulders were noted to have fatty infiltration of the teres minor. The rate of isolated fatty infiltration of the teres minor was 0.4%. Concomitant deltoid muscle atrophy was common, and occurred in 68% of the shoulders with fatty infiltration of the teres minor. Tearing of the teres minor tendon was extremely rare.

Conclusion

Fatty infiltration of the teres minor can occur in isolation, be associated with deltoid muscle atrophy only, or occur in the setting of rotator cuff full tears. Thus, fatty infiltration of the teres minor may be related to a neurologic process or disuse. Further long term longitudinal studies are necessary to be elucidate the etiologies.

Level of Evidence

Level IV.

Thoracic Outlet Syndrome in the Overhead Athlete: Diagnosis and Treatment Recommendations

PURPOSE OF REVIEW

Neurovascular compression in the upper extremity is rare but can affect even those participating in high-level competitive athletics. To assess optimal approaches to treatment, in this review, we evaluate the current literature on neurovascular compressive syndromes affecting the upper extremity, with a special focus on the thoracic outlet syndrome (TOS).

RECENT FINDINGS

Neurovascular compression at the thoracic outlet can involve the brachial plexus, subclavian artery, or subclavian vein, each with distinct clinical manifestations. Neurogenic TOS is best treated with surgical decompression, if physical therapy has not improved symptoms. Venous TOS results in acute thrombosis superimposed on chronic venous compression. Treatment is best directed at early anticoagulation, catheter-directed thrombolysis, and surgical decompression, with most patients able to discontinue anticoagulation and return to high-level athletic activity. Arterial TOS is related to aneurysmal degeneration of the subclavian artery with distal embolization, leading to limb-threatening ischemia. This should be aggressively treated with surgery. Similar degenerative changes can occur in the axillary artery and its branches, leading to distal embolization. Prompt recognition of these potential sources of limb-threatening ischemia is critical to limb preservation. TOS includes rare but important conditions in the overhead athlete. Recent advances in physical therapy and image-guided diagnostic techniques have facilitated more accurate diagnosis. Surgical treatment remains the gold standard to maximize function or for limb preservation, and future research is needed to clarify optimal pain and physiotherapy regimens, as well as to examine novel approaches to neurovascular decompression.

Current concepts review: peripheral neuropathies of the shoulder in the young athlete

Peripheral neuropathies of the shoulder and upper extremity are uncommon injuries that may affect the young athletic population. When present, they can result in significant pain and functional impairment. The cause of peripheral neuropathy in young athletes may be an acute, traumatic injury such as a shoulder dislocation or a direct blow to the shoulder girdle. Alternatively, repetitive overuse with resultant compression or traction of a nerve over time may also result in neuropathy; overhead athletes and throwers may be particularly susceptible to this mechanism of nerve injury. Regardless of etiology, young athletes typically present with activity-related pain, paresthesias, and dysfunction of the affected upper extremity. In addition to physical examination, diagnostic studies such as radiographs and magnetic resonance imaging (MRI) are commonly performed as part of an initial evaluation and electrodiagnostic studies may be used to confirm the diagnosis of peripheral neuropathy. Electrodiagnostic studies may consist of electromyography, which evaluates the electrical activity produced by skeletal muscles, and/or a nerve conduction study, which evaluates a nerve's ability to transmit an electrical signal. Although data are not robust, clinical outcomes for young patients with activity-related peripheral neuropathies of the shoulder are generally good, with most young athletes reporting both symptomatic and functional improvement after treatment.

Overview of arterial pathology related to repetitive trauma in athletes

BACKGROUND/OBJECTIVE

Sport-related vascular trauma is an important consequence of increased physical activity. Repetitive, high-intensity movements predispose athletes to vascular disease, including arterial pathology, by exerting increased pressure on neurovascular structures. This is an important source of morbidity in an otherwise young and healthy population. Arterial pathology associated with repetitive trauma is often misdiagnosed as musculoskeletal injury. This article increases awareness of sport-related arterial disease by reviewing the symptomatology, investigation, and treatment modalities of this pathology. In addition, prognostic outcomes specific to the athlete are discussed.

RESULTS

Arterial thoracic outlet syndrome and vascular quadrilateral space syndrome are associated with athletes involved in overhead throwing exercises. Sport-related arterial pathology of the lower limb include external iliac artery endofibrosis (EIAE), popliteal artery entrapment syndrome (PAES), and adductor canal syndrome. Vascular stress and kinking secondary to vessel tethering are important contributors to pathology in EIAE. Chronic exertional compartment syndrome must also be considered, presenting with clinical features similar to PAES. In addition, athletes are predisposed to blunt mechanical trauma. Hypothenar hammer syndrome is one such example, contributing to a high burden of morbidity in this population.

CONCLUSIONS

In arterial thoracic outlet syndrome and vascular quadrilateral space syndrome, surgery is advocated in symptomatic individuals, with postoperative outcomes favorable for the athlete. Acute limb ischemia may occur as a result of secondary thrombosis or embolization, often without preceding claudication. PAES and adductor canal syndrome are associated with functional entrapment in the athlete, secondary to muscular hypertrophy. Surgical exploration may be indicated. Poorer outcomes are noted when this process is associated with vascular reconstruction. Surgical treatment of EIAE follows failure of conservative management, with limited data available on postoperative prognosis. Investigations for all these conditions should be targeted based on clinical suspicion. A delay in diagnosis can have severe consequences on return to competition in these high-functioning individuals.

Acute traumatic quadrilateral space syndrome following scapula fracture

The acute tunnel syndrome of the quadrilateral space of Velpeau is a very rare entity in which the axillary nerve and the posterior humeral circumflex artery experience brutal compression in shoulder injuries. We report the case of a burst fracture of the right scapula with great displacement of the lateral border occasioning a total isolated paralysis of the right axillary nerve by axillary nerve compression. The lateral scapula border fracture was reduced and stabilized with neurolysis of the axillary nerve through a posterior approach. The recovery of the axillary nerve occurred in ten weeks. Our case is original, not only because of the rarity of isolated axillary nerve injury follwing scapula fractures without shoulder dislocation, but also because the compression of the axillary nerve by bone impingement could be undiagnosed and comprise prognosis.

Fluoroscopic-guided quadrilateral space block for the treatment of quadrilateral space syndrome - A case report

We report a case of a 48-year-old female who presented four months following a low-energy trauma with symptoms most consistent with adhesive capsulitis. An MRI demonstrated extensive patchy areas of intramuscular edema-like signal involving the lateral head of the deltoid with associated muscle atrophy, in keeping with a subacute denervation injury. She was diagnosed with quadrilateral space syndrome (QSS) and successfully treated with an fluoroscopic-guided corticosteroid injection. At her two-year follow-up, the patient had regained full function and had no lasting symptoms. Non-specific symptoms like ill-defined shoulder pain, decreased motor function, and weakness can delay the diagnosis and management of QSS. As there is a lack of a good diagnostic study, fluoroscopic-guided quadrilateral space block should be considered should the diagnosis fit a patient's clinical profile, as this has the potential to be both diagnostic and therapeutic.

A systematic review on posterior circumflex humeral artery pathology: sports and professions at risk and associated risk factors

INTRODUCTION

Posterior circumflex humeral artery (PCHA) aneurysm formation and thrombosis as overuse injury in the dominant shoulder can result in ischemia of the forearm, hand and digits due to arterial embolisms. Increased awareness among physicians is necessary as PCHA pathology (PCHAP) might be underdiagnosed. Knowledge of sports and professions at risk and risk-factors for obtaining PCHAP is essential for the development of future preventive measures. This study aims to identify sports and professions at risk as well as risk factors for PCHAP.

EVIDENCE ACQUISITION

The databases of MEDLINE, EMBASE, BIOSIS, CINAHL and SPORTDiscus were systematically searched.

EVIDENCE SYNTHESIS

Twenty-seven papers fulfilled the inclusion criteria and described 67 patients with PCHAP involved in seven sports and three professions. The sports (number of cases) were volleyball (41), baseball (13), swimming (1), tennis (3), American football (2), canoeing (1) and yoga (1) (2 unknown). The professions included a baseball coach, a circus trapeze artist and a mechanic. Apart from expert opinions, no studies have identified risk factors for PCHAP. An anatomic variation of the PCHA origin is suggested to be protective for PCHAP.

CONCLUSIONS

PCHAP is reported in seven overhead sports and three professions. No risk factors for PCHAP were identified. An anatomic variant of the PCHA origin was found to be a potential protective factor for PCHAP. Physicians should be cautious for distal embolization as a result of PCHAP in athletes and workers, both adult and adolescent, involved in repetitive powerful overhead movements.

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.

Understanding the Importance of the Teres Minor for Shoulder Function: Functional Anatomy and Pathology

Although the teres minor is often overlooked in a normal shoulder, it becomes a key component in maintaining shoulder function when other rotator cuff tendons fail. The teres minor maintains a balanced glenohumeral joint and changes from an insignificant to the most significant external rotator in the presence of major rotator cuff pathology. The presence or absence of the teres minor provides prognostic information on the outcomes of reverse total shoulder arthroplasty and tendon transfers. Clinical tests include the Patte test, the Neer dropping sign, the external rotation lag sign, and the Hertel drop sign. Advanced imaging of the teres minor can be used for classification using the Walch system. Understanding the function and pathology surrounding the teres minor is paramount in comprehensive management of the patient with shoulder pathology. Appropriate clinical examination and imaging of the teres minor are important for preoperative stratification and postoperative expectations.

Quadrilateral Space Syndrome With Involvement of the Tendon of the Latissimus Dorsi

Quadrilateral space syndrome (QSS) is the term used to describe axillary nerve palsy due to compression of the axillary nerve and posterior circumflex artery in the quadrilateral space. The precise pathophysiology of QSS is still unclear; hence, a consensus of diagnosis and treatment for QSS has not yet been achieved. The authors present the case of a 17-year-old male baseball player with symptoms of QSS, including right elbow and shoulder joint pain and upper limb numbness while throwing. The symptoms had worsened during baseball. Conservative management for 3 months failed to resolve the symptoms, so surgery was performed. Axillary nerve decompression resulted in functional improvement. The cause of QSS has been previously reported to be fibrous bands, the long head of the triceps, and Bennett lesions. However, the cause of QSS in this case was compression of the axillary nerve between the proximal humerus and the tendinous attachment of the latissimus dorsi. The authors incised a 10- to 15-mm segment of the medial edge of the tendinous insertion of the latissimus dorsi, which resulted in resolution of QSS symptoms. [Orthopedics. 2017; 40(4):e714-e716.].

Vascular Quadrilateral Space Syndrome in 3 Overhead Throwing Athletes: An Underdiagnosed Cause of Digital Ischemia

Vascular quadrilateral space syndrome (vQSS) is an underdiagnosed cause of extremity ischemia, pain, and paresthesia in overhand throwing athletes. The mechanism of vQSS is thought to result from repeated abduction and external rotation of the arm leading to a distraction injury of the posterior circumflex humoral artery (PCHA) as this courses through the quadrilateral space. This trauma may cause dissection and dissecting aneurysm formation. Thrombus from this arterial injury then embolizes down the arm resulting in the symptomatic presentation. Patients were often presented after multiple embolic events, which have resulted in obliteration of digital arteries. Later stages of presentation may include ischemic ulceration and gangrene. We report 3 cases of vQSS in overhand throwing athletes. All 3 underwent surgical correction and have returned to competition. We discuss presentation, diagnosis, imaging findings, management, outcomes, and review of the literature. Prompt recognition of this syndrome is essential to optimal treatment, which includes PCHA ligation and division with or without thrombolytic therapy. Increased awareness of vQSS is needed among coaches and athletic trainers who often identify the symptoms and initiate the treatment. When treated promptly, these athletes return to baseline functional status.

Anatomy of the terminal branch of the posterior circumflex humeral artery: relevance to the deltopectoral approach to the shoulder

AIMS

Despite the expansion of arthroscopic surgery of the shoulder, the open deltopectoral approach is increasingly used for the fixation of fractures and arthroplasty of the shoulder. The anatomy of the terminal branches of the posterior circumflex humeral artery (PCHA) has not been described before. We undertook an investigation to correct this omission.

PATIENTS AND METHODS

The vascular anatomy encountered during 100 consecutive elective deltopectoral approaches was recorded, and the common variants of the terminal branches of the PCHA are described.

RESULTS

In total, 92 patients (92%) had a terminal branch that crossed the space between the deltoid and the proximal humerus and which was therefore vulnerable to tearing or avulsion during the insertion of the blade of a retractor during the deltopectoral approach to the shoulder. In 75 patients (75%) there was a single vessel, in 16 (16%) a double vessel and in one a triple vessel.

CONCLUSION

The relationship of these vessels to the landmark of the tendon of the insertion of pectoralis major into the proximal humerus is described. Damage to these previously undocumented branches can cause persistent bleeding leading to prolonged surgery and post-operative haematoma and infection, as well as poor visualisation during the procedure. Cite this article: Bone Joint J 2016;98-B:1395-8.

Beyond the Cuff: MR Imaging of Labroligamentous Injuries in the Athletic Shoulder

Shoulder disease is common in the athletic population and may arise as a consequence of a single traumatic episode or multiple repeated events. Associated labroligamentous injuries can result in substantial disability. Specific athletic and occupational activities result in predictable injury patterns. Imaging in general and magnetic resonance (MR) imaging, in particular, are vital in establishing the correct diagnosis and excluding common mimicking conditions, to ensure timely and appropriate management. In this review, the utility of MR imaging and MR arthrography will be explored in evaluation of shoulder disease, taking into account normal variants of the labroligamentous complex. Subsequently, broad categories of labral lesions and instability, external and internal impingement, as well as nerve entrapment syndromes, will be discussed, while emphasizing their imaging findings in the clinical context and illustrating key features. More recent concepts of internal impingement and secondary subacromial impingement will also be clarified.

Reproducibility of the SPI-US protocol for ultrasound diameter measurements of the Posterior Circumflex Humeral Artery and Deep Brachial Artery: an inter-rater reliability study

OBJECTIVES

Elite overhead athletes are at risk of posterior circumflex humeral artery (PCHA) degeneration, aneurysm formation and thrombosis. Identification of the proximal PCHA and the nearby originating deep brachial artery (DBA) can be a challenge, even among experienced sonographers. The aim of this study was to assess the accuracy and precision of a newly designed standardized ultrasound (US) protocol (SPI-US) for assessment of the PCHA and DBA.

METHODS

Two experienced sonographers determined diameters of the PCHA and DBA using the SPI-US protocol. Inter-observer agreement was evaluated using intra-class correlation coefficient (ICC), standard error of measurement (SEM), minimal detectable change (MDC), Bland-Altman (BA) analysis, and variance component (VARCOMP) analysis.

RESULTS

Thirty-three healthy volunteers participated. The ICC for diameter measurement of the PCHA and DBA were 0.70 (95 %CI 0.50-0.83) and 0.60 (95 %CI 0.30-0.80), respectively. The SEM for the PCHA and DBA was 0.32 mm and 0.29 mm and MDC was 0.90 mm and 0.80 mm, respectively. The BA and VARCOMP analyses showed no systematic and only marginal sonographer bias.

CONCLUSIONS

The SPI-US protocol is accurate and precise for PCHA and DBA diameter assessment in cases where they originate from the axillary artery. PCHA and DBA diameter measurements are sonographer-independent using the SPI-US-protocol.

KEY POINTS

• PCHA & DBA diameter assessment is accurate and reliable using the SPI-US protocol • PCHA & DBA diameter measurements are sonographer-independent using the SPI-US protocol • The SPI-US protocol minimal detectable change is 0.90 mm for PCHA diameter measurement • This minimal detectable change enables detection of PCHA aneurysms • First step towards international periodic surveillance of athletes at risk of PCHA-injury.

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.

Ultrasound-guided quadrilateral space block for the diagnosis of quadrilateral syndrome

Quadrilateral space syndrome (QSS) is a rare nerve entrapment disorder that occurs when the axillary nerve and posterior circumflex humeral artery (PCHA) become compressed in the quadrilateral space. QSS presents as vague posterolateral shoulder pain that is exacerbated upon the abduction and external rotation of the shoulder. Diagnosis of QSS is difficult because of the vague presentation of QSS. In addition, even though MRI and MR angiography can be used in QSS diagnosis, there is currently no "gold standard" diagnostic imaging studies for QSS. In this case report, we describe a novel ultrasound-guided technique for a diagnostic quadrilateral space block and present a case where the diagnostic block was used to diagnose QSS. We believe that a diagnostic block of the quadrilateral space is a useful adjunct in the evaluation of patients with suspected QSS, especially in cases where examination findings and other diagnostic modalities are indeterminate.

Understanding and evaluating shoulder pain in the throwing athlete

Shoulder pain in the throwing athlete can present at any age and in any level of sport and can lead to dysfunction. A thorough evaluation of the throwing athlete can often determine the cause of symptoms, which is frequently multifactorial. Although the pathophysiology leading to pain in the shoulder of the throwing athlete is not entirely known, nonoperative modalities remain the mainstay of treatment. In general, surgical intervention should be reserved as a last resort. Effective treatment often requires collaboration among trainers, players, physicians, and therapists to determine an appropriate course of action.

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.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

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.

[Nerve compression syndrome of the shoulder : Arthroscopic decompression procedures]

Several nerve compression syndromes have been described in the literature involving compression of the axillary nerve in the quadrangular space and most importantly compression of the suprascapular nerve in the suprascapular as well as the spinoglenoid notch. This article describes the arthroscopic techniques of nerve decompression around the shoulder.

Ultrasound of the posterior circumflex humeral artery

Quadrilateral space syndrome (QSS) is described as compression neuropathy of the axillary neurovascular bundle in the quadrilateral space of the shoulder. This neurovascular bundle includes the posterior circumflex humeral artery (PCHA). Historically, angiography and more recently magnetic resonance angiography have been used to assess occlusion and stenosis of the PCHA in cases of suspected QSS. These traditional imaging techniques have a number of disadvantages in terms of cost, availability, invasiveness and patient comfort. We undertook to examine the ability of ultrasound to reliably visualise the PCHA. Asymptomatic adult volunteers were recruited from staff, and patients attending the radiology department who presented for pathologies unrelated to the shoulder. We used a new technique to assess blood flow in the PCHA, performing the scan from a posterolateral approach on the upper arm just above the level of the surgical neck of the humerus. This technique enabled the scan to be undertaken with the patient seated comfortably. Fifty volunteers were recruited into the study. The mean (+/-SD) age was 35 (+/-14 years). The PCHA was visualised in all patients. Our method was able to maximise Doppler sensitivity and visualisation of the artery without discomfort to the patient in less than 10 min. Ultrasound can be used to reliably visualise the PCHA. Ultrasound has potential to be used in the assessment of the PCHA in cases of QSS.

Triangular interval syndrome: A differential diagnosis for upper extremity radicular pain

This case report describes a 57-year-old female who experienced symptoms of scapular pain with pain radiating into the right upper extremity. Initial medical referral suggested, nerve entrapment of a cervical origin. However, the patient did not fit the clinical prediction rule for cervical radiculopathy. Radial nerve bias was positive without cervical provocation, with symptom reproduction at the lateral scapular area. Treatment addressed mechanical dysfunction at the triangular interval formed by the teres major and triceps, comprising manual therapy, neural mobilization, corrective exercise and pain modalities. Reduction in symptoms was observed with a decrease in right scapular and arm pain and improved radial nerve mobility. The triangular interval is described as a predominant contributor to the symptomatology secondary to entrapment and adverse neural tension of the radial nerve. The anatomical and physiological basis is enumerated.

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.