Definition

By: Gregory R. Waryasz, MD

The flexor digiti minimi brevis muscle of the musculoskeletal system is characterized by being variable in size.

It is part of the hypothenar muscles.  It consists of skeletal muscle fibers.

Its unique structural features include it lying lateral to the abductor dignity minimi.

The origin is the hook of the hamate and flexor retinaculum.

The insertion is the medial side of the base of the proximal phalanx of the 5th digit.

The blood supply is from the ulnar artery and venous drainage is from the accompanying veins.

The innervation is from the deep branch of the ulnar nerve.

The flexor digiti minimi brevis muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the flexor digiti minimi brevis is to flex the proximal phalanx of the 5th digit.  The synergists are the flexor digitorum superficialis, flexor digitorum profundus, and the opponens digiti minimi.

Common diseases include ulnar nerve palsy.

Ulnar nerve palsy can occur at any point of the course of the ulnar nerve leading to weakness and sensory changes.  Numbness and tingling can occur in the distribution of the ulnar nerve.

Commonly used diagnostic procedures include clinical history, physical exam, EMG, and MRI.

It is usually treated with bracing, NSAIDs, physical therapy, and corticosteroid injections for ulnar nerve palsy syndrome.

References

Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.

Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.

Wheeless’ Textbook of Orthopaedics: Flexor Digiti Minimi Brevis (http://www.wheelessonline.com/ortho/flexor_digiti_minimi_brevis)