open access

Ahead of Print
Case report
Published online: 2021-03-22
Submitted: 2020-11-05
Accepted: 2021-03-05
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Pointing in a different direction: a case of bilateral absence of extensor indicis

A. Ma, J. Kim, C. E. Miller, T. L. Mustapich, J. P. Abraham, S. A. Downie, P. L Mishall
DOI: 10.5603/FM.a2021.0030
·
Pubmed: 33778941

open access

Ahead of Print
CASE REPORTS
Published online: 2021-03-22
Submitted: 2020-11-05
Accepted: 2021-03-05

Abstract

Understanding anatomical variations, as well as, normal anatomy of the muscles and tendons of the hand is vital for successful clinical evaluation and surgery. A number of extensor muscle and tendon variations have been reported in the literature including duplication, triplication, and absence. We report a rare anatomical variation that includes bilateral absence of the extensor indicis (EI) muscles and bilateral duplication of the extensor digitorum (ED) tendon to the second digit in the forearm of an 83-year-old male cadaver during routine upper limbs dissection. In the present case, only three muscles were present in the deep compartment: extensor pollicis longus (EPL), extensor pollicis brevis (EPB), and abductor pollicis longus (APL) with bilateral absence of EI. The reported prevalence of bilateral absence of EI muscle and tendon ranges from 0.5 to 3.5%  [1, 26]. The prevalence of an additional index tendon arising bilaterally from the ED muscle belly is 3.2 % of the population [1]. Extension of the index finger is governed by the actions of EI and ED. However, the four tendons of ED are linked to each other by juncturae tendinum (JT), restricting independent extension of the digits in certain postures, e.g. when the hand is fisted. With fisted hand, EI controls extension of the index finger. Clinically, EI tendons are used for tendon reconstruction procedures to restore function to the hand and thumb after trauma or tendon rupture. This report highlights the importance of anticipating anatomical variations and conducting pre-operative evaluations to confirm the presence of EI when planning tendon transfer procedures.

Abstract

Understanding anatomical variations, as well as, normal anatomy of the muscles and tendons of the hand is vital for successful clinical evaluation and surgery. A number of extensor muscle and tendon variations have been reported in the literature including duplication, triplication, and absence. We report a rare anatomical variation that includes bilateral absence of the extensor indicis (EI) muscles and bilateral duplication of the extensor digitorum (ED) tendon to the second digit in the forearm of an 83-year-old male cadaver during routine upper limbs dissection. In the present case, only three muscles were present in the deep compartment: extensor pollicis longus (EPL), extensor pollicis brevis (EPB), and abductor pollicis longus (APL) with bilateral absence of EI. The reported prevalence of bilateral absence of EI muscle and tendon ranges from 0.5 to 3.5%  [1, 26]. The prevalence of an additional index tendon arising bilaterally from the ED muscle belly is 3.2 % of the population [1]. Extension of the index finger is governed by the actions of EI and ED. However, the four tendons of ED are linked to each other by juncturae tendinum (JT), restricting independent extension of the digits in certain postures, e.g. when the hand is fisted. With fisted hand, EI controls extension of the index finger. Clinically, EI tendons are used for tendon reconstruction procedures to restore function to the hand and thumb after trauma or tendon rupture. This report highlights the importance of anticipating anatomical variations and conducting pre-operative evaluations to confirm the presence of EI when planning tendon transfer procedures.

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Keywords

extensor indicis, forearm, congenital, index finger, hand

About this article
Title

Pointing in a different direction: a case of bilateral absence of extensor indicis

Journal

Folia Morphologica

Issue

Ahead of Print

Article type

Case report

Published online

2021-03-22

DOI

10.5603/FM.a2021.0030

Pubmed

33778941

Keywords

extensor indicis
forearm
congenital
index finger
hand

Authors

A. Ma
J. Kim
C. E. Miller
T. L. Mustapich
J. P. Abraham
S. A. Downie
P. L Mishall

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