Teres Minor-Why is it Important?

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

GENERAL ANATOMY

• The teres minor is a small, narrow muscle of the rotator cuff.

• It is located on the posterior aspect of the shoulder.

• Functions primarily as an external rotator of the shoulder and contributes to glenohumeral stability.

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TRIANGULAR SPACE

Boundaries

• Superior: Lower border of the teres minor

• Inferior: Teres major

• Lateral: Long head of the triceps brachii

Contents

• Circumflex scapular artery

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QUADRANGULAR SPACE

Boundaries

• Superior: Teres minor

• Inferior: Teres major

• Medial: Long head of the triceps brachii

• Lateral: Surgical neck of the humerus

Contents

• Axillary nerve

• Posterior circumflex humeral artery

Imaging

• Best visualized on sagittal section magnetic resonance imaging.

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INNERVATION

• Supplied by the posterior branch of the axillary nerve.

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FUNCTION

• External rotation of the shoulder joint.

• Stabilization of the humeral head within the glenoid during arm movements.

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CLINICAL EXAMINATION

Hornblower Test

• The patient is seated or standing.

• The examiner positions the shoulder in 90 degrees of abduction in the scapular plane.

• The elbow is flexed to 90 degrees.

• The patient is asked to externally rotate the arm against resistance.

Positive Test

• Weakness or pain during resisted external rotation.

• Suggests teres minor dysfunction or tear.

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SURGICAL IMPORTANCE

• The teres minor is an important anatomical landmark in the posterior approach to the shoulder joint.

• Preservation of the muscle and its nerve supply is essential during posterior surgical exposures.

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TERES MINOR ATROPHY

Causes

• Idiopathic muscle atrophy

• Quadrangular space syndrome, due to compression of the axillary nerve

• Associated rotator cuff pathology

Clinical Significance

• Atrophy leads to weakness in external rotation.

• Often identified incidentally on magnetic resonance imaging.

• May contribute to posterior shoulder pain and functional impairment.

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CLINICAL RELEVANCE

• The teres minor plays a key role in posterior shoulder stability.

• Pathology may be overlooked but has significant implications for shoulder function.

• Knowledge of the surrounding spaces is critical in:

  • Trauma

  • Tumor surgery

  • Nerve compression syndromes

  • Posterior shoulder approaches