| Extensor indicis proprius | |
|---|---|
 | |
 Posterior surface of the left forearm. Deep muscles. Extensor indicis muscle is labeled in purple. | |
| Details | |
| Origin | Posterior distal third ofulna andinterosseous membrane |
| Insertion | Index finger (extensor hood) |
| Artery | Posterior interosseous artery |
| Nerve | Posterior interosseous nerve |
| Actions | Extendsindex finger,wrist |
| Identifiers | |
| Latin | musculus extensor indicis |
| TA98 | A04.6.02.052 |
| TA2 | 2515 |
| FMA | 38524 |
| Anatomical terms of muscle | |
Inhuman anatomy, theextensor indicis (proprius) is a narrow, elongatedskeletal muscle in the deep layer of the dorsalforearm, placed medial to, and parallel with, theextensor pollicis longus. Its tendon goes to theindex finger, which it extends.
It arises from the distal third of the dorsal part of thebody of ulna and from theinterosseous membrane. It runs through the fourth tendon compartment together with theextensor digitorum, from where it projects into the dorsalaponeurosis of the index finger.[1]
Opposite the head of thesecond metacarpal bone, it joins the ulnar side of the tendon of the extensor digitorum which belongs to the index finger.
Like theextensor digiti minimi (i.e. the extensor of the little finger), the tendon of the extensor indicis runs and inserts on the ulnar side of the tendon of the common extensor digitorum.[2] The extensor indicis lacks thejuncturae tendinum interlinking the tendons of the extensor digitorum on the dorsal side of the hand.[3]
The extensor indicis proprius does not show much variation. It exists as a single tendon most of the time.[4] Double tendons of the extensor indicis proprius was also reported.[2][5][6]
It is known that the extensor indicis proprius inserts to the index finger on the ulnar side of the extensor digitorum.[7] However, the insertion on the radial side of the common extensor digitorum infrequently seen, namely theextensor indicis radialis.[2] Split tendons of the muscle inserting on both ulnar and the radial side of the common extensor digitorum was also reported.[2]
Anomalous hand extensors including theextensor medii proprius and theextensor indicis et medii communis are often seen as variations of the extensor indicis[2] due to the shared characteristics and embryonic origin.[8]
The extensor indicisextends theindex finger, and by its continued action assists in extending (dorsiflexion) thewrist and themidcarpal joints.[1]
Because the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers.[3]
This article incorporates text in thepublic domain frompage 456 of the 20th edition ofGray's Anatomy(1918)
