Definition
By: Gregory R. Waryasz, MD
The flexor digitorum profundus muscle of the musculoskeletal system is characterized by being the only muscle that can flex the distal interphalangeal joint.
It is part of the forearm. It consists of skeletal muscle fibers.
Its unique structural features include it being a thick muscle that covers the anterior ulna. The flexor digitorum profundus divides into four tendons that go to each of the four fingers by entering into the fibrous tendon sheath of the finger.
At the mid-palmar area, the flexor digitorum superficialis tendons are more volar than the flexor digitorum profundus. As the tendons become more distal, the flexor digitorum superficialis becomes more dorsal than the flexor digitorum profundus as the flexor digitorum profundus continues on to its more distal insertion site.
The origin is the proximal three-fourths of the medial and anterior surfaces of the ulna and interosseous membrane.
The insertion is the base of the distal phalanges of the medial four phalanges after passing trhough the flexor digitorum superficialis tendons.
The blood supply is from the anterior interosseous artery and venous drainage is from the accompanying veins.
The innervation is from the anterior interosseous nerve to the lateral part of the flexor digitorum profundus and from the ulnar nerve to the medial part of the flexor digitorum profundus.
The flexor digitorum profundus 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 digitorum profundus is to flex the distal phalanges of the four medial phalanges at the distal interphalangeal joint. The tendon also helps to flex the metacarpophalangeal joint and the wrist joint. The synergist is the flexor digitorum superficialis.
Common diseases include tendon rupture, tenosynovitis, and Jersey finger.
Tendon rupture can occur with trauma.
Tenosynovitis of the flexor tendons can lead to the trigger finger phenomenon.
Jersey finger occurs when the flexor tendon is avulsed from the bony insertion point of the flexor digitorum profundus. The tendon can retract into the palm or the bony fragment may prevent retraction.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, and MRI.
It is usually treated with rest, NSAIDs, physical therapy, splinting, and corticosteroid injection for tenosynovitis. Tenosynovitis causing a triggering phenomenon may require a release of the A1 pulley. Tendon rupture may require surgery. The Jersey finger can be treated with surgery. The type of surgical repair depends upon where the tendon retracts to in the finger or palm
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 Digitorum Profundus (http://www.wheelessonline.com/ortho/flexor_digitorum_profundus)