Folia Morphologica

open access

Ahead of Print
CASE REPORTS
Published online: 2019-06-04
Submitted: 2019-03-05
Accepted: 2019-05-29
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Novel, bilateral, two-bellied muscles span the extensor forearm, thenar eminence to insert on the proximal phalanx of the thumb: clinical and embryological significance

Priti L. Mishall, Amber N. Marsh, Diana Perez, Xavier H. Quezada, Maximilian C. Stahl, Rachel E. Weinstock, Sherry A. Downie
DOI: 10.5603/FM.a2019.0067
·
Pubmed: 31169299

open access

Ahead of Print
CASE REPORTS
Published online: 2019-06-04
Submitted: 2019-03-05
Accepted: 2019-05-29

Abstract

Muscle and tendon variations in the forearm, wrist and hand are commonly reported in the anatomical and surgical literature. They are frequently the source of inflammatory conditions such as de Quervain’s tenosynovitis or carpal tunnel syndrome. During academic dissection, a cadaver presented with bilateral, additional muscles running parallel to the abductor pollicis longus muscles (APL) in the extensor compartment of the forearm. Both additional muscles had two bellies, one proximal and one distal, with an intervening tendon. The proximal bellies were separate and distinct from the adjacent APLs. The tendons traversed the first dorsal compartments with the tendons of the APLs and the extensor pollicis brevis muscles (EPB). The distal bellies lay adjacent to the abductor pollicis brevis (APB) muscles in the thenar compartments, and inserted onto the volar base of the proximal phalanges of the thumbs. Following a thorough search of the literature, we determined that these additional muscles constitute a previously unreported variation. This report details the variation, compares it with other reported variations, presents the related embryology, and reviews the significance of this variation as it relates to inflammatory conditions and surgical procedures.

Abstract

Muscle and tendon variations in the forearm, wrist and hand are commonly reported in the anatomical and surgical literature. They are frequently the source of inflammatory conditions such as de Quervain’s tenosynovitis or carpal tunnel syndrome. During academic dissection, a cadaver presented with bilateral, additional muscles running parallel to the abductor pollicis longus muscles (APL) in the extensor compartment of the forearm. Both additional muscles had two bellies, one proximal and one distal, with an intervening tendon. The proximal bellies were separate and distinct from the adjacent APLs. The tendons traversed the first dorsal compartments with the tendons of the APLs and the extensor pollicis brevis muscles (EPB). The distal bellies lay adjacent to the abductor pollicis brevis (APB) muscles in the thenar compartments, and inserted onto the volar base of the proximal phalanges of the thumbs. Following a thorough search of the literature, we determined that these additional muscles constitute a previously unreported variation. This report details the variation, compares it with other reported variations, presents the related embryology, and reviews the significance of this variation as it relates to inflammatory conditions and surgical procedures.

Get Citation

Keywords

novel muscles, extensor compartment forearm, de Quervain’s syndrome

About this article
Title

Novel, bilateral, two-bellied muscles span the extensor forearm, thenar eminence to insert on the proximal phalanx of the thumb: clinical and embryological significance

Journal

Folia Morphologica

Issue

Ahead of Print

Published online

2019-06-04

DOI

10.5603/FM.a2019.0067

Pubmed

31169299

Keywords

novel muscles
extensor compartment forearm
de Quervain’s syndrome

Authors

Priti L. Mishall
Amber N. Marsh
Diana Perez
Xavier H. Quezada
Maximilian C. Stahl
Rachel E. Weinstock
Sherry A. Downie

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