. 2015 Jun 30;15(61):172–188. doi: 10.15557/JoU.2015.0015

Tab. 5.

Fourth Compartment. Anatomy review

Fourth compartment
ED – extensor digitorum (extensor digitorum communis and extensor indicis proprius) Origin: lateral epicondyle of humerus, common extensor tendon Insertion: extensor expansion of middle and distal phalanges of 2nd, 3rd, 4th and 5th fingers Blood supply: posterior interosseous artery Nerve: radial nerve Actions: extension of the phalanges (mainly the proximal phalanges), then the wrist, and finally the elbow. ED tends to separate the fingers as it extends them. Tips and tricks: 1. The middle and terminal phalanges are extended mainly by the interossei and lumbricales. 2. Mallet finger – injury of ED tendon at the distal interpharyngeal joint DIP. Mallet finger usually is caused by an object (e.g., a ball) striking the finger, creating a forceful flexion of the extended DIP. The extensor tendon may be stretched, partially torn, or completely ruptured or separated by a distal phalanx avulsion fracture.

Fourth compartment

Anatomy review

ED – extensor digitorum (extensor digitorum communis and extensor indicis proprius)
Origin: lateral epicondyle of humerus, common extensor tendon
Insertion: extensor expansion of middle and distal phalanges of 2nd, 3rd, 4th and 5th fingers
Blood supply: posterior interosseous artery
Nerve: radial nerve
Actions: extension of the phalanges (mainly the proximal phalanges), then the wrist, and finally the elbow. ED tends to separate the fingers as it extends them.
Tips and tricks:
1. The middle and terminal phalanges are extended mainly by the interossei and lumbricales.
2. Mallet finger – injury of ED tendon at the distal interpharyngeal joint DIP. Mallet finger usually is caused by an object (e.g., a ball) striking the finger, creating a forceful flexion of the extended DIP. The extensor tendon may be stretched, partially torn, or completely ruptured or separated by a distal phalanx avulsion fracture.