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ORIGINAL ARTICLES
Published online: 2018-10-03
Submitted: 2018-05-06
Accepted: 2018-06-24
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Accessory head of the flexor pollicis longus muscle: anatomical study and clinical significance

Daniel R. Ballesteros, Pedro L. Forero, Luis E. Ballesteros
DOI: 10.5603/FM.a2018.0091
·
Pubmed: 30299534

open access

Ahead of Print
ORIGINAL ARTICLES
Published online: 2018-10-03
Submitted: 2018-05-06
Accepted: 2018-06-24

Abstract

Background: The accessory head of the flexor pollicis longus (AHFPL) has an oblique trajectory from medial to lateral aspect of the forearm below the flexor digitorum superficialis muscle and then joins the flexor pollicis longus muscle. When the anterior interosseous nerve (AIN) courses underneath the muscle belly of the AHFPL an entrapment neuropathy may occur, known as anterior interosseous nerve syndrome (AINS).

Materials and methods: This descriptive cross-sectional study evaluated 106 fresh upper extremities. When the AHFPL was present, its fascicle was traced up to evaluate the origin site. The morphometric variables were measured using a digital micrometer (Mitutoyo, Japan). The relationship between the AHFLP and the AIN was evaluated.

Results: The AHFPL was found in 34 (32.1%) of the 106 forearms. The AHFPL arose from the flexor digitorum superficialis muscle in 16 forearms (47.1%), the medial epicondyle of the humerus in ten forearms (29.4%) and the coronoid process of ulna in eight forearms (23.5%). The average total length of the AHFPL was 94.11 ± 10.33 mm. The AIN was located lateral to the AHFPL in three forearms (8.8%), posterolateral in seven forearms (20.6%) and posterior in 24 forearms (70.6%).

Conclusions: This study performed in a South American population sample revealed a prevalence of the AHFPL in a lower range compared to previous studies in North Americans and Asians. The AIN coursed more frequently underneath the muscle belly of AHFPL. This finding has clinical significance in the onset of the AINS and the subsequent surgical procedure for the AIN decompression.

Abstract

Background: The accessory head of the flexor pollicis longus (AHFPL) has an oblique trajectory from medial to lateral aspect of the forearm below the flexor digitorum superficialis muscle and then joins the flexor pollicis longus muscle. When the anterior interosseous nerve (AIN) courses underneath the muscle belly of the AHFPL an entrapment neuropathy may occur, known as anterior interosseous nerve syndrome (AINS).

Materials and methods: This descriptive cross-sectional study evaluated 106 fresh upper extremities. When the AHFPL was present, its fascicle was traced up to evaluate the origin site. The morphometric variables were measured using a digital micrometer (Mitutoyo, Japan). The relationship between the AHFLP and the AIN was evaluated.

Results: The AHFPL was found in 34 (32.1%) of the 106 forearms. The AHFPL arose from the flexor digitorum superficialis muscle in 16 forearms (47.1%), the medial epicondyle of the humerus in ten forearms (29.4%) and the coronoid process of ulna in eight forearms (23.5%). The average total length of the AHFPL was 94.11 ± 10.33 mm. The AIN was located lateral to the AHFPL in three forearms (8.8%), posterolateral in seven forearms (20.6%) and posterior in 24 forearms (70.6%).

Conclusions: This study performed in a South American population sample revealed a prevalence of the AHFPL in a lower range compared to previous studies in North Americans and Asians. The AIN coursed more frequently underneath the muscle belly of AHFPL. This finding has clinical significance in the onset of the AINS and the subsequent surgical procedure for the AIN decompression.

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Keywords

flexor pollicis longus; anterior interosseous nerve; nerve compression syndromes, anatomic variation, orthopedic procedures

About this article
Title

Accessory head of the flexor pollicis longus muscle: anatomical study and clinical significance

Journal

Folia Morphologica

Issue

Ahead of Print

Published online

2018-10-03

DOI

10.5603/FM.a2018.0091

Pubmed

30299534

Keywords

flexor pollicis longus
anterior interosseous nerve
nerve compression syndromes
anatomic variation
orthopedic procedures

Authors

Daniel R. Ballesteros
Pedro L. Forero
Luis E. Ballesteros

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