orthopedic surgery app

ORTHOFIXAR | Orthopedic Surgery Learning App

orthopedic surgery app android orthopedic surgery app ios
Extensor Digitorum Communis Muscle Anatomy - Upper Limb

Hello Surgeon

X

How can we help you today?

Post

Extensor Digitorum Communis Muscle Anatomy – Upper Limb

Content List

The extensor digitorum communis muscle (EDC), the principal extensor of the medial four digits of the hand, occupies much of the posterior surface of the forearm. It’s located in the superficial compartment of the posterior forearm.

Extensor Digitorum Communis Muscle Anatomy

The extensor digitorum muscle arises from the lateral epicondyle of the humerus, by the common extensor tendon; from the intermuscular septa between it and the adjacent muscles, and from the antebrachial fascia.

See Also: Forearm Muscles Anatomy & Function

Proximally, its four tendons join the tendon of the extensor indicis to pass deep to the extensor retinaculum through the tendinous sheath of the extensor digitorum and extensor indicis (common extensor synovial sheath). On the dorsum of the hand, the tendons spread out as they run toward the digits.

Extensor Digitorum Communis Muscle Anatomy

Adjacent tendons are linked proximal to the knuckles (metacarpophalangeal joints) by three oblique intertendinous connections that restrict independent extension of the four medial digits (especially the ring finger). Consequently, normally none of these digits can remain fully flexed as the other ones are fully extended. Commonly, the fourth tendon is fused initially with the tendon to the ring finger and reaches the little finger by an intertendinous connection.

Extensor Digitorum Communis tendon - wrist

On the distal ends of the metacarpals and along the phalanges of the four medial digits, the four tendons flatten to form extensor expansions. Each extensor digital expansion (dorsal expansion or hood) is a triangular, tendinous aponeurosis that wraps around the dorsum and sides of a head of the metacarpal and proximal phalanx. The visor-like “hood” formed by the extensor expansion over the head of the metacarpal, holding the extensor tendon in the middle of the digit, is anchored on each side to the palmar ligament (a reinforced portion of the fibrous layer of the joint capsule of the metacarpophalangeal joints).

Extensor Digitorum Communis tendon hand

In forming the extensor expansion, each extensor digitorum tendon divides into a median band, which passes to the base of the middle phalanx, and two lateral bands, which pass to the base of the distal phalanx. The tendons of the interosseous and lumbrical muscles of the hand join the lateral bands of the extensor expansion.

See Also: Hand Anatomy, Bones & Muscles

The retinacular ligament is a delicate fibrous band that runs from the proximal phalanx and fibrous digital sheath obliquely across the middle phalanx and two interphalangeal joints. It joins the extensor expansion to the distal phalanx. During flexion of the distal interphalangeal joint, the retinacular ligament becomes taut and pulls the proximal joint into flexion. Similarly, on extending the proximal joint, the distal joint is pulled by the retinacular ligament into nearly complete extension.

extensor expansion

The extensor digitorum communis acts primarily to extend the proximal phalanges, and through its collateral reinforcements, it secondarily extends the middle and distal phalanges as well. After exerting its traction on the digits, or in the presence of resistance to digital extension, it helps extend the hand at the wrist joint.

OriginLateral epicondyle of humerus
InsertionExtensor expansions of medial four digits
InnervationPosterior interosseous nerve (C7 and C8)
The continuation of the deep branch of the radial nerve (C7, C8)
Blood SupplyInterosseous recurrent and posterior interosseous arteries
ActionExtends medial four digits at metacarpophalangeal joints;
Extends hand at wrist joint

Clinically

To test the extensor digitorum communis, the forearm is pronated and the fingers are extended. The person attempts to keep the digits extended at the metacarpophalangeal joints as the examiner exerts pressure on the proximal phalanges by attempting to flex them. If acting normally, the extensor digitorum can be palpated in the forearm, and its tendons can be seen and palpated on the dorsum of the hand.

References & More

  1. Clinically Oriented Anatomy – 8th Edition
  2. Clinical Anatomy by Regions, Richard S. Snell.
  3. Hu X, Suresh NL, Xue C, Rymer WZ. Extracting extensor digitorum communis activation patterns using high-density surface electromyography. Front Physiol. 2015 Oct 6;6:279. doi: 10.3389/fphys.2015.00279. PMID: 26500558; PMCID: PMC4593961. Pubmed
Angle Meter App for Android & iOS
  • Lifetime product updates
  • Install on one device
  • Lifetime product support
One-Click Purchase
Orthopedic FRCS VIVAs Quiz
  • Lifetime product updates
  • Install on one device
  • Lifetime product support
One-Click Purchase
Top 12 Best Free Orthopedic Apps
  • Lifetime product updates
  • Install on one device
  • Lifetime product support
One-Click Purchase
All-in-one Orthopedic App
  • Lifetime product updates
  • Install on one device
  • Lifetime product support
One-Click Purchase