Definition
By: Gregory R. Waryasz, MD
The flexor pollicis brevis muscle of the musculoskeletal system is characterized by its superficial and deep muscle bellies.
It is part of the thenar muscles. It consists of skeletal muscle fibers.
Its unique structural features include it being composed of a superficial and deep muscle belly. It is located medial to the abductor pollicis brevis. The deep belly is often referred to as the first palmar interosseous muscle
The origin is the flexor retinaculum and tubercles of the scaphoid and trapezium.
The insertion is the lateral side of the base of the proximal phalanx of the thumb.
The blood supply is from the arteries of the superficial palmar arch and venous drainage is from the accompanying veins.
The innervation is from the recurrent branch of the median nerve nerve to the superficial head. The deep head is innervated by the deep branch of the ulnar nerve.
The flexor pollicis 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 pollicis brevis is to flex the thumb at the proximal phalanx. The continued action flexes the 1st metacarpal and rotates it medially. It can aide in opposition. The synergists are the flexor pollicis longus and the adductor pollicis.
Common diseases include carpal tunnel syndrome.
Carpal tunnel syndrome is a compressive neuropathy of the median nerve at the wrist. It can lead to weakness in the hand and decreased sensation in the palm. Patients often report numbness and tingling in the palm and distribution of the median nerve. Long-standing carpal tunnel can lead to atrophy of the muscles innervated by the median nerve distal to the compressive neuropathy.
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 carpal tunnel syndrome. A carpal tunnel surgical release procedure can often reduce the compressive neuropathy.
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 Pollicis Brevis (http://www.wheelessonline.com/ortho/flexor_pollicis_brevis)