Definition

By: Gregory R. Waryasz, MD

The dorsal interossei of the musculoskeletal system is characterized by being 4 muscles.

It is part of the intrinsic hand muscles.  It consists of skeletal muscle fibers.

The unique structural features include being four separate muscles.

The origins are the adjacent sides of two metacarpals.

The insertions are the bases of the proximal phalanges and the extensor expansions of the 2nd through 4th digits.

The blood supply is from the arterial branches of the palmar arches and venous drainage is from the accompanying veins.

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

The dorsal interossei as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the dorsal interossei are to abduct the 2nd through 4th fingers from the axial line.  They act along with the lumbricals to flex the metacarpophalangeal joints and to extend the interphalangeal joints. The synergists are the lumbricals, palmar interossei, flexor digitorum profundus, and the flexor digitorum superficialis.

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.