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Concept: Quadrangular space

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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.

Concepts: Muscle, Exercise, Physical therapy, Exercise physiology, Massage, Axillary nerve, Posterior humeral circumflex artery, Quadrangular space

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Quadrilateral space syndrome (QSS) is a rare orthopedic condition caused by compression, entrapment, or injury to the axillary nerve or posterior humeral circumflex artery as they arise from the quadrilateral space. QSS can present with point tenderness over the quadrilateral space and weakness and paresthesia in the axillary nerve distribution. It is commonly associated with repetitive overhead activities and is seen in athletes engaging in such activities. Here we report a case of QSS in a 42-year-old male weight lifter who presented with pain and soreness in the posterior aspect of his right shoulder radiating around his arm as well as slight weakness of his right shoulder of a few weeks duration. MRI results of his shoulder demonstrated moderate atrophy and fatty infiltration of the teres minor. His diagnosis of QSS was confirmed with electro diagnostic testing which showed axillary neuropathy. He was treated with ultrasound guided corticosteroid injections and gained relief from this treatment. His axillary neuropathy was shown to be resolving on repeat electro diagnostic testing at six-months follow-up. Here we report a case of QSS and provide a brief review of the literature.

Concepts: Neurology, Pain, Rotator cuff, Teres minor muscle, Deltoid muscle, Axillary nerve, Posterior humeral circumflex artery, Quadrangular space

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We present a case of quadrilateral space syndrome (QSS) in a patient with left arm pain. The patient sustained a trauma to his left arm, and QSS was successfully diagnosed by physical examination, magnetic resonance image, electromyographic evaluation, and nerve conduction studies. Surgery was performed to decompress the axillary nerve and the patient recovered fully with minimal residual symptoms.

Concepts: Medical terms, Hospital, Nuclear magnetic resonance, Nerve conduction study, Brachial plexus, Axillary nerve, Quadrangular space, Surgical neck of the humerus

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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. 201x; xx(x):xx-xx.].

Concepts: Humerus, Elbow, Latissimus dorsi muscle, Deltoid muscle, Axillary nerve, Glenohumeral joint, Posterior humeral circumflex artery, Quadrangular space

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Variations in the innervation of the posterior deltoid muscle by the anterior branch of the axillary nerve have been reported. The objective of this study is to clarify the anatomy of the axillary nerve branches to the deltoid muscle. One hundred and twenty-nine arms (68 right and 61 left) from 88 embalmed cadavers (83 male and 46 female) were included in the study. The anterior and posterior branches of the axillary nerve were identified and their lengths were measured from the point of emergence from the axillary nerve to their terminations in the deltoid muscle. In all cases, the axillary nerves split into two branches (anterior and posterior) within the quadrangular space and none split within the deltoid muscle. In all specimens, the anterior and middle parts of the deltoid muscle received their nerve supplies from the anterior branch of the axillary nerve. The posterior part of the deltoid muscle was supplied only by the anterior branch of the axillary nerve in 2.3% of the specimens, from the posterior branch in 8.5%, and from both branches in 89.1%. There were two sub-branches of the anterior branch in 4.7% of the specimens. The anterior branch of the axillary nerve supplied not only the anterior and middle parts of the deltoid muscle but also the posterior part in most cases (91.5%). Clin. Anat., 2014. © 2014 Wiley Periodicals, Inc.

Concepts: Muscle, Nerve, Deltoid muscle, Axillary nerve, Deltoid tuberosity, Quadrangular space

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Surgery to transfer the axillary nerve and the nerve of the long head of the triceps presents two obstacles: 1) the access portals are not standardized and 2) the nerves are for their larger part approached through large incisions. The goal of this study was to explore the feasibility of an endoscopic microsurgical approach. The posterior aspect of a cadaver shoulder was approached through three communicating mini-incisions. The Da Vinci robot camera was installed on a central trocart, and the instrument arms on the adjacent trocarts. A gas insufflation distended the soft tissues up to the lateral axillary space. The branches of the axillary nerve and the nerve to the long head of the triceps brachii muscle were identified. The dissection of the axillary nerve trunk and its branches was easy. The posterior humeral circumflex veins and artery were dissected as well without any difficulty. Finding the nerve to the long head of the triceps brachii was found to be more challenging because of its deeper location. Robots properties allow performing conventional microsurgery: elimination of the physiologic tremor and multiplication of the movements. They also facilitate the endoscopic approach of the peripheral nerves, as seen in our results on the terminal branches of the axillary nerve and the nerve to the long head of the triceps brachii.

Concepts: Surgery, Biceps brachii muscle, Elbow, Triceps brachii muscle, Ulna, Deltoid muscle, Radial nerve, Quadrangular space