The extensor indicis et medii communis is a rare anatomical variant in the extensor compartment of

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...

. This additional muscle lies in the deep extensor layer next to the

extensor indicis proprius In human anatomy, the extensor indicis roprius'' is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it ex ...

and the

extensor pollicis longus In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with ...

. The characteristics of this anomalous muscle resemble those of the

, with split tendons to the index and the middle finger. This muscle can also be considered as a variation of the aberrant

extensor medii proprius The extensor medii proprius (so called the ''extensor digiti medii'') is a rare anatomical variant in the extensor compartment of the forearm. The aberrant muscle is analogous to the extensor indicis with the insertion being the middle finger inst ...

Structure

The extensor indicis et medii communis originates from the distal third of

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

next to the

. After passing the wrist joint through the fourth extensor compartment, the tendon splits into two to insert to the

extensor expansion An extensor expansion (extensor hood, dorsal expansion, dorsal hood, dorsal aponeurosis) is the special connective attachments by which the extensor tendons insert into the phalanges. These flattened tendons (aponeurosis) of extensor muscles spa ...

of the index and the middle finger.

Prevalence

The extensor indicis et medii communis has an incidence between 0% and 6.5%.

Meta-analysis A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...

showed that the muscle was present in average of 1.6% of the total 3,760 hands, and was more prevalent in North American populations.

Structure

Prevalence

Function

See also

References

External links