Quadrilateral Space Syndrome: An Evidence-Based Approach

Failing to meet objective goals creates unhappy patients.  But instead of throwing up your hands, think of these frustrating moments as opportunities.  Treating a shoulder mimics peeling an onion - new diagnoses appear as muscle compensations and pain subside.  Don’t be surprised during a re-evaluation when your diagnosis changes.  Orthopedic findings may direct care to a different course.  A patient’s response to a given treatment allows you to learn more about the hobbies, habits, and movements that affect their condition.  Our most significant clinical asset is the ability to EVALUATE and RE-EVALUATE.

Quadrilateral Space Syndrome (QSS), aka Quadrangular Space Syndrome, an under-recognized condition that can test our diagnostic ability. QSS is frequently misdiagnosed as cervical radiculopathy or shoulder impingement. Check out the following video to watch Dr. Steele describe the current best practice evaluation, treatment, and management of QSS.

What is QSS?

QSS describes symptoms associated with the compression or irritation of the axillary nerve and the posterior circumflex humeral artery. Patients report vague symptoms of shoulder pain, with tenderness over the quadrilateral space upon palpation.  Longstanding compression may lead to denervation with subsequent loss of shoulder abduction (deltoid) or external rotation (teres minor).

Where is QSS?

The axillary nerve is the direct continuation of the posterior cord of the brachial plexus. Its fibers arise from the C5 and C6 spinal nerve roots. The nerve lies anterior to the subscapularis muscle, then descends inferiorly, exiting the axilla posteriorly through the “quadrilateral space”- bounded superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the humerus. (1) After exiting the quadrangular space along with the posterior circumflex artery, the nerve supplies a motor branch to the teres minor and another that courses around the posterior humerus to innervate the deltoid. A sensory branch supplies cutaneous innervation to the inferior deltoid region.

What causes QSS?

Abduction and external rotation of the shoulder traction the contents of the quadrilateral space and thereby compress the nerve and artery. Anatomic features including fibrous bands are a common finding in the quadrilateral space, being present in 14 of 16 shoulders. (2) The most common site for a fibrous band is between the teres major and the long head of the triceps. These bands can compress the nerve and artery during internal and external rotation of the shoulder.

What are the clinical symptoms?

QSS often presents with poorly localized shoulder pain and paresthesia over the lateral aspect of the shoulder and arm in a non-dermatomal pattern. Physical examination will demonstrate point tenderness over the quadrilateral space. Teres minor and deltoid weakness is possible. Sustained external rotation and abduction will exacerbate symptoms. (3) Activities like brushing or washing hair are common mechanical sensitivities.  Repetitive overhead motions can also create or exacerbate QSS. (3) Repetitive vascular trauma may rarely cause a dissecting aneurysm or thrombus. (4)

How is QSS managed?

Conservative management affords good outcomes for the majority of patients. (5) Overhead athletes may benefit from selective rest and activity modification. (6) Alteration of throwing mechanics is a successful management tool in 75-90% of patients. (7,8) Range of motion exercises may be implemented to prevent joint contracture. (5) Conservative care may include myofascial release techniques to the muscles of the quadrangular space, glenohumeral mobilization, cross body and posterior capsule/ internal rotation stretching, and rotator cuff strengthening. (6) Clinicians should be cautious to avoid positions that place the axillary nerve in a state of sustained traction (i.e., late cocking).

What if the patient doesn’t get better?

Axillary nerve injuries heal slowly, and surgical intervention should only be considered until conservative management fails to restore muscle function in three to six months. (5) Surgical intervention includes neurolysis and release of aberrant fibrous bands. A nerve graft is an option in cases of neurotmesis. Surgical outcomes are typically good. (1)

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• References

  1. Kline DG, Kim DH: Axillary nerve repair in 99 patients with 101 stretch injuries. J Neurosurg 99:630–636, 20

  2. Flynn LS, et al. Quadrilateral space syndrome: a review. J Shoulder Elbow Surg. 2017.

  3. Chang PS, et al. Quadrilateral Space Syndrome Treated with Ultrasound-Guided Corticosteroid Injection: A Case of Isolated Teres Minor Atrophy and Review of the Literature. S D Med. 2017.

  4. Rollo J, et al. Vascular Quadrilateral Space Syndrome in 3 Overhead Throwing Athletes: An Underdiagnosed Cause of Digital Ischemia. Ann Vasc Surg. 2017.

  5. Pasila M, Jaroma H, Kiviluoto O, Sundholm A: Early complications of primary shoulder dislocations. Acta Orthop Scand 49:260–263, 1978

  6. Hoskins WT at el. Quadrilateral space syndrome: A case study and review of the literature. British Journal of Sports Medicine 2005; 39 E9.

  7. Cormier PJ, Matalon TA, Wolin PM: Quadrilateral space syndrome: a rare cause of shoulder pain. Radiology 167:797–798, 1988

  8. Duralde XA: Neurologic injuries in the athlete's shoulder. J Athl Train 35:316–328, 2000