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. 2017 Dec 19;18(1):539.
doi: 10.1186/s12891-017-1901-x.

Anatomical variations of the palmaris longus muscle including its relation to the median nerve - a proposal for a new classification

Łukasz Olewnik  1 , Grzegorz Wysiadecki  2 , Michał Polguj  3 , Michał Podgórski  4 , Hubert Jezierski  5 , Mirosław Topol  2
Affiliations

Anatomical variations of the palmaris longus muscle including its relation to the median nerve - a proposal for a new classification

Łukasz Olewnik et al. BMC Musculoskelet Disord. .

Abstract

Background: The palmaris longus (PL) muscle is characterised by high morphological diversity, and its tendon crosses the median nerve (MN) at different levels. Due to the fact that the palmaris longus tendon is routinely harvested for reconstruction of other tendons, knowledge of its morphological variations is clinically important. Therefore, the purpose of the study was to suggest a new morphological classification of the PL muscle and characterise the relationship of its tendon to the median nerve.

Methods: Standard dissection was performed on 80 randomised and isolated upper limbs (40 left and 40 right) fixed in a 10% formalin solution. Measurements of muscle belly and tendon were obtained. The course and location of tendon insertion, as well as its relationship to the median nerve, were noted.

Results: The palmaris longus muscle was present in 92.5% of specimens. Three types of palmaris longus muscle were identified based on the morphology of its insertion (types I-III) and these were further subdivided into three subgroups (A-C) according to the ratio of the length of the muscle belly and its tendon. The most frequent was type I (78.8%), where the tendon attached to the palmar aponeurosis, and subtype B, where the tendon-to-belly ratio was 1-1.5 (41.1%). The mean distance from the interstyloid line to the crossing between the median nerve and the palmaris longus tendon was 31.6 mm. In addition, two types of palmaris longus were described.

Conclusion: The presented classification of palmaris longus muscle types allows a better characterization of its diversity and may be useful in planning tendon grafting.

Keywords: New classification; Palmaris longus muscle; Palmaris longus tendon; Tendon grafts.

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Conflict of interest statement

Ethics approval and consent to participate

The protocol of the study was accepted by Bioethics Committee of Medical University of Lodz (resolution RNN/92/16/KE). The cadavers belong to the Department of Normal and Clinical Anatomy of the Medical University of Lodz. Each of the persons who died prematurely signed a notarial consent for the use of corpses for scientific and research purposes.

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Palmaris longus muscle. a Type I of the palmaris longus muscle. Right forearm. b Type II of the palmaris longus muscle. Left forearm. c Type III of the palmaris longus muscle. Right forearm. PL palmaris longus muscle, PA palmar aponeurosis, FCU flexor carpi radialis muscle, md medial division of the tendon of palmaris longus muscle, ld lateral division of the tendon of palmaris longus muscle
Fig. 2
Fig. 2
Insertion of the tendon of palmaris longus muscle. a Insertion of Type I of the palmaris longus muscle. Left forearm. b insertion of type II of the palmaris longus muscle. Left forearm. c Insertion of type III of the palmaris longus muscle. Right forearm. tPL tendon palmaris longus muscle, MN Median nerve, PA palmar aponeurosis, md medial division of the tendon of palmaris longus muscle, ld lateral division of the tendon of palmaris longus muscle, FCU Flexor carpii radialis
Fig. 3
Fig. 3
Muscle with low pinnate. The white arrowheads indicate the pennation. PM palmaris longus muscle, tPL tendon palmaris longus muscle
Fig. 4
Fig. 4
Relationship between median nerve (MN) and the tendon of the palmaris longus muscle (tPL)
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