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A novel accessory muscle in the flexor compartment of anterior forearm inserting into the tenosynovium of the flexor pollicis longus
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, United States
- Department of Physical Medicine and Rehabilitation, Albert Einstein College of Medicine, Bronx, NY, United States
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY, United States
open access
Abstract
A common variant of accessory muscles in the anterior forearm is the Gantzer’s muscle (GM). GM arises as a muscle belly from flexor digitorum superficialis (FDS) or ulnar coronoid process to merge distally with the flexor pollicis longus (FPL) muscle. In the present case report, we describe a novel accessory muscle in the flexor compartment of the forearm. The proximal attachment was tendinous and came from three sources: FDS muscle, ulnar coronoid process, and the medial aspect of the proximal radius. The distal tendon of the novel accessory muscle ran parallel to FPL, passed through the carpal tunnel, and entered the palmar aspect of the hand. In the hand, the tendon thinned out and blended with the tenosynovium of the FPL, contributing to the sheath around the FPL tendon. This accessory muscle of the FPL is comparable to the frequently documented GM; however, the present case exhibited fundamental nuances that distinguish it from the previously described iterations of the GM in the following ways: 1) The novel accessory muscle is tendinous from its proximal origin and throughout the upper one-third of the forearm, and one component of its origin arose from the medial aspect of the radius. GMs with an origin on the radius have not been previously reported. 2) In the middle one-third, the tendinous proximal attachment transitioned to a muscle belly that passed through the carpal tunnel and entered the hand. 3) In the hand, the novel tendon widened, thinned, and merged with the tenosynovium of the FPL. Accessory muscles are a common finding in the anterior forearm during cadaveric dissection. In patients, they can be the cause of neuropathies due to compression of the anterior interosseous nerve. Awareness of variations is also important for clinicians who examine the forearm and hand, as well as hand surgeons.
Abstract
A common variant of accessory muscles in the anterior forearm is the Gantzer’s muscle (GM). GM arises as a muscle belly from flexor digitorum superficialis (FDS) or ulnar coronoid process to merge distally with the flexor pollicis longus (FPL) muscle. In the present case report, we describe a novel accessory muscle in the flexor compartment of the forearm. The proximal attachment was tendinous and came from three sources: FDS muscle, ulnar coronoid process, and the medial aspect of the proximal radius. The distal tendon of the novel accessory muscle ran parallel to FPL, passed through the carpal tunnel, and entered the palmar aspect of the hand. In the hand, the tendon thinned out and blended with the tenosynovium of the FPL, contributing to the sheath around the FPL tendon. This accessory muscle of the FPL is comparable to the frequently documented GM; however, the present case exhibited fundamental nuances that distinguish it from the previously described iterations of the GM in the following ways: 1) The novel accessory muscle is tendinous from its proximal origin and throughout the upper one-third of the forearm, and one component of its origin arose from the medial aspect of the radius. GMs with an origin on the radius have not been previously reported. 2) In the middle one-third, the tendinous proximal attachment transitioned to a muscle belly that passed through the carpal tunnel and entered the hand. 3) In the hand, the novel tendon widened, thinned, and merged with the tenosynovium of the FPL. Accessory muscles are a common finding in the anterior forearm during cadaveric dissection. In patients, they can be the cause of neuropathies due to compression of the anterior interosseous nerve. Awareness of variations is also important for clinicians who examine the forearm and hand, as well as hand surgeons.
Keywords
Gantzer, forearm, flexor pollicis longus, carpel tunnel
Title
A novel accessory muscle in the flexor compartment of anterior forearm inserting into the tenosynovium of the flexor pollicis longus
Journal
Issue
Article type
Case report
Pages
515-519
Published online
2021-04-09
Page views
6008
Article views/downloads
1099
DOI
Pubmed
Bibliographic record
Folia Morphol 2022;81(2):515-519.
Keywords
Gantzer
forearm
flexor pollicis longus
carpel tunnel
Authors
A. Gurvich
N. Shridhar
A. Felman
M. Shi
A. Pinkas
S. A. Downie
P. L Mishall
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