Morphological Study of Palmaris Longus Muscle

Home , Forearm, Hand, Palmaris longus muscle, Pronator teres muscle, Thenar eminence

International International Archives of Medicine 2017 Medical Society Section: Human Anatomy Vol. 10 No. 215 http://imedicalsociety.org ISSN: 1755-7682 doi: 10.3823/2485

Humberto Ferreira Morphological Study of Palmaris Arquez1 Longus Muscle ORIGINAL 1 University of Cartagena. University St. Thomas. Professor Human Morphology, Medicine Program, University of Pamplona. Morphology Laboratory Abstract Coordinator, University of Pamplona.

Background: The palmaris longus is one of the most variable muscle Contact information: in the human body, this variations are important not only for the ana- tomist but also radiologist, orthopaedic, plastic surgeons, clinicians, Humberto Ferreira Arquez. therapists. In view of this significance is performed this study with Address: University Campus. Kilometer the purpose to determine the morphological variations of palmaris 1. Via Bucaramanga. Norte de Santander, longus muscle. Colombia. Suramérica. Tel: 75685667-3124379606.

Methods and Findings: A total of 17 cadavers with different age groups were used for this study. The upper limbs region (34  [email protected] sides) were dissected carefully and photographed in the Morphology Laboratory at the University of Pamplona. Of the 34 limbs studied, 30 showed normal morphology of the palmaris longus muscle (PL) (88.2%); PL was absent in 3 subjects (8.85% of all examined forearm). Unilateral absence was found in 1 male subject (2.95% of all examined forearm); bilateral agenesis was found in 2 female subjects (5.9% of all examined forearm). Duplicated palmaris longus muscle was found in 1 male subject (2.95 % of all examined forearm). The palmaris longus muscle was innervated by branches of the median nerve. The accessory palmaris longus muscle was supplied by the deep branch of the ulnar nerve. Palmaris longus is a muscle located Keywords in the superficial layer of the anterior compartment of the forearm. Anatomical Variation, Palmaris It has a small belly arising from the medial epicondyle of the hu- Longus Muscle, Accessory merus, and its long thin tendon inserts into the palmar aponeurosis Palmaris Longus Muscle, in the hand, the muscle has importance in medical clinic, surgery, Agenesis Palmaris Longus radiological analysis, in studies about high-performance athletes, in Muscle, Clinical Significance, genetics and anthropologic studies. Median Nerve, Ulnar Nerve.

Conclusions: The anatomical variations of the palmaris longus muscle must be documented of their clinical significance and their potential use in orthopaedic and reconstructive surgery.

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Introduction fleshy throughout or its tendon may be split and The Palmaris longus muscle (PL) belongs to the su- sometimes it may be degenerated to such an extent perficial flexor muscles of the forearm. The mus- it that may be simply represented by a tendinous cles of the forearm are: 1) the anterior or flexors; band. When it is tendinous proximally and has a 2) the posterior or abductors; and 3) the muscles fleshly distal belly it is called reverse PL or PL inver- of the radial area. All these muscles are muscular sus [8]. The objectives of the present study were to at the upper end and they are toggled into long determine the morphological variations of palmaris thin tendons that extend at the apex of the fin- longus muscle and clinical significance. gers. The PL muscle belongs to the anterior muscles of the forearm. The anterior muscles form three layers, two superficial and one deep. This muscle Methods belongs to the first superficial layer along with the This work was previously approved by the Ethics flexor carpi ulnaris, the flexor carpi radialis and the Committee in Research and Environmental Impact pronator teres muscles [1]. The PL muscle is a thin of the University of Pamplona, conformed by re- spindle shaped long slender and fusiform muscle solution 030 of January 16, 2014 and Resolution that is found between the flexor carpi ulnaris and No. 008430 of October 4 of 1993, issued by the flexor carpi radialis. It arises from the medial epicon- Ministry of Health of Republic of Colombia by dyle and epicondylar ridge of the humerus. It runs which regulates the scientific, technical and admi- downwards and terminates in a long, slender ten- nistrative norms for health research. This descrip- don which passes anterior to the transverse carpal tive cross-sectional study was designed to deter- ligament, crosses the retinaculum, becomes flat and mine the prevalence and morphologic features of enters the palmar aponeurosis of the hand, ante- the anatomical variations of the Palmaris Longus rior to the flexor retinaculum. Its innervation comes muscle in 34 upper extremities of 15 male and 2 from branches of the median nerve [2]. females embalmed adults cadavers in the labora- The PL muscle flexes the wrist weakly as an acces- tory of Morphology of the University of Pamplona. sory flexor muscle. Its main function is to serve as The flexor compartment of the upper limb were an anchor of the fascia, as it tenses the skin and the studied serially during the years 2014-2016. The palmar fascia of the hand, shearing the forces to the anatomical variation described was found during palmar aponeurosis in a distal direction. Another routine dissection performed by medical students use of the muscle is to abduct the thumb. This role of second semester in a 47-year-old male cada- is due to its slender move over the long adaptor of ver. Measurements were taken with assistance of the thumb. Generally, its role is negligible and this is a sliding Vernier caliper, accurate to 1 mm during the reason why it is lost in many operations without the course of the anatomical dissection. The data cost to the function of the forearm or the wrist [1-3]. thus obtained were recorded in a physical matrix A wide range of anatomical variations of the and were consigned in digital media using Excel muscles, vascular and nervous in the upper limb tables. Topographic details of the variations were has been reported in anatomical, clinical and ra- examined, recorded and photographed. diological studies [4-7]. Numerous variations of the PL muscle have been reported in both morphology and number. It may have a proximal tendon or a Results distal tendon, or have a fleshy central belly with Of the 34 limbs studied, 30 showed normal mor- proximal and distal tendons, it may be digastric or phology of the Palmaris longus muscle (PL) (88.2%);

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Figure 1: Anterior view of the left forearm.

BR: Brachiorradialis muscle; FCR: flexor carpi radialis muscle; FCU: Flexor carpi ulnaris; PL: Palmaris longus muscle, inserted into apex of palmar aponeurosis; Acc PL: Accessory Palmaris Longus muscle inserted in to flexor retinaculum

PL was absent in 3 subjects (8.85% of all examined llowed by a long tendon distally at the middle of forearm), of which: unilateral absence was found the forearm. The tendon coursed over the flexor in 1 male subject (2.95% of all examined forearm); retinaculum, finally inserting into the palmar apo- bilateral agenesis was found in 2 female subjects neurosis. The morphology of the Acc PL was quite (5.9% of all examined forearm). Duplicated PL mus- similar to that of the PL (Figure 1). cle was found in 1 male subject (2.95 % of all exa- The muscle belly measuring 110 mm in length mined forearm). and 11 mm in width was followed by the tendon distally at the middle of forearm, and finally inser- Palmaris longus and accessory palmaris ting into the flexor retinaculum (Table 1). longus muscle in the left forearm Table 1. Summary of Palmaris longus and Accessory The Accessory Palmaris Longus muscle (Acc PL) palmaris longus muscle in the left forearm was found ulnar to the Palmaris longus muscle (PL). Palmaris longus Accessory palmaris The bellies of both the Acc PL and PL were closely Morphology apposed with each other towards proximal; the muscle longus muscle tendons of both the Acc PL and PL were separated Length 125 mm Length 110 mm Muscle belly towards distal in 102 mm. The duplicate PL arose Width 12.6 mm Width 11 mm from a common tendinous origin of flexor mus- Length 145 mm Length 125 mm cles [PL, flexor carpi radialis muscle (FCR), flexor Tendon Width 6.2 mm Width 4.8 mm carpi ulnaris muscle (FCU), pronator teres muscle Thickness 1.3 mm Thickness 0.8 mm (PT) and a part of the flexor digitorum superficia- Origin Medial epicondyle Medial epicondyle lis muscle (FDS)] at the medial epicondyle of the Insertion Palmar aponeurosis Flexor retinaculum humerus. In the PL, the muscle belly measuring 125 mm in length and 12.6 mm in width was fo- Innervation Median nerve Ulnar nerve

The PL was innervated by branches of the median would affect the hand functions or not. Palmaris nerve in the proximal third of the forearm. The Acc longus was reported to play an important role in PL muscle passed superficial to the ulnar artery and thumb abduction through an extension onto the ulnar nerve, and was supplied by the deep branch thenar eminence [9-11]. It is also believed that a of the ulnar nerve. The branches to the FCR, PL and weak flexor of the wrist and divided palmaris lon- FDS arose as a common trunk from the median gus is of little importance and need not to be re- nerve, whereas those to the Acc PL and FDS arose paired. It has been determined that grip strength as another common trunk which branched distally. of the hand wrist was not affected in the absence of PL. It has been reported that patients requiring a palmaris longus tendon graft could be divided Discussions into two main groups depending on the functional The PL muscle has great clinical importance and is status of the donor’s upper extremity [10, 11]. In classified phylogenetically as a retrogressive muscle. the first group, the donor’s upper extremity was The reasons for its importance are: 1) its tendon normal and the palmaris longus was needed for is a great landmark to identify the median nerve reconstruction elsewhere, e.g., lip augmentation, during operations; 2) the PL tendon is used as an ptosis correction, management of facial paralysis, alternative transplant for various cosmetic and re- tendon reconstruction in the opposite extremity, constructive plastic surgery, hand procedures and etc. The second group of patients was those in as a tendon graft in various positions in otolaryn- whom the donor’s upper extremity was not nor- gology and ophthalmology (e.g. lip augmentation, mal. This group could further be subdivided into ptosis correction, management of facial paralysis, two subgroups: one where the primary pathology restoration of lip and chin defects, urinary inconti- did not involve the wrist flexors or thumb abductor nence, opponensplasty for severe carpal tunnel syn- muscles, e.g., ulnar collateral ligament reconstruc- drome and excisional arthroplasty for management tion, interposition tendon grafts, and carpometa- of Keinbock’s disease), repair of tendon calcanei, carpal (CMC) joint arthroplasty and the other sub- collapsed lunate replacement, auto graft for ruptu- group included those patients where the primary red extensor tendons, acute thenar injury–Camitz pathology involved the wrist flexors or thumb ab- opponensplasty [3]. PL muscle variations cause a ductor muscles, e.g., high ulnar and low median variety of clinical syndromes such as carpal tunnel nerve palsies. The probable effects of the palma- syndrome, Guyon’s syndrome or compartment syn- ris longus muscle on hand functions have been drome of the forearm or the wrist, may be associa- studied and no clinically significant difference was ted with the symptoms of Dupuytren’s contracture, observed [10,11]. Answer the question of whether accessory palmaris longus muscle that appeared to the functional value of the palmaris longus muscle compress the ulnar nerve during repeated contrac- bears a statistical value and significance in healthy tions and hypertrophy of the palmaris longus mus- subjects or not. To this end, reviewing both grip cle seen as an pseudomass of the forearm ; and 4) and pinch strengths. As for the grip strength, research of the PL muscle helps the understanding the presence or absence of the palmaris longus of the hereditary of genes responsible for the mus- muscle did not create a difference in general. In cles and their functions [3, 8]. both sexes, the palmaris longus muscle increased The frequent use of the palmaris longus ten- pinch strength in the fourth and fifth fingers of don by surgeons brings to mind the question of the hands (especially in the right hand). Based on whether the removal of the tendon of this muscle these findings, it can be concluded that thepal -

4 This article is available at: www.intarchmed.com and www.medbrary.com International Archives of Medicine 2017 Section: Human Anatomy Vol. 10 No. 215 ISSN: 1755-7682 doi: 10.3823/2485 maris longus muscle may impact the opposition Conclusion movement of the fingers [11]. The knowledge of these variations is significant for Some authors consider what functionally, though radiologist, orthopaedic, plastic surgeons, clinicians, the muscle is primarily a wrist flexor, acting as an therapists is important in clinical diagnosis and sur- adjunct to digital flexion at the metacarpophalan- gical practice, since these muscles have potential geal joint, observation lend credence to the obser- use in orthopaedic and reconstructive surgery and vation that the distal tendinous segments of the their variations may be implicated in the etiopatho- muscle aid in fixing the open-ended mobile end of logy of neuromuscular symptoms and morphologi- the long axis around which supination of forearm is cal alterations in the forearm. executed. Shifting of the distal terminus of the axis in the complex articulations of the supination - pro- Acknowledgements nation kinetics, is facilitated by the proximal, middle The author thanked to the University of Pamplo- and distal radio-ulnar joints through the divergent na for research support and/or financial support; fibrous extensions of the aponeurosis, by the ten- at National Institute of Legal Medicine and Foren- dinous insertion of the palmaris longus muscle [12]. sics Sciences and Erasmo Meoz University Hospital Several authors have described the PL muscle as a in Cúcuta, North of Santander, Colombia for the mere phylogenetically degenerate metacarpopha- donation of cadavers identified, unclaimed by any langeal flexor because of its clinical insignificance family, or persons responsible for their care, process and its numerous anatomical variations. However, subject to compliance with the legal regulations in the less common variants can lead to pathological the Republic of Colombia. conditions due to the narrow topographical relationship between the PL and the median nerve, cau- Competing interests sing median nerve compression. Understanding the None. anatomical variations of the PL is important because it often plays a crucial role during reconstructive Research Support and/or Financial surgeries due to its suitable length and diameter, Support ease of harvest and lack of donor site morbidity. It University of Pamplona is the responsible institution is essential to clinically examine reconstructive patients for potential PL anatomical variations to avoid inappropriate surgical procedures and prevent di- References sappointing surgical results [1]. 1. Murabit A, Gnarra M, Mohamed A. Reversed palmaris longus muscle: Anatomical variant - case report and literature review. The vascularity of the palmaris longus is most Can J Plast Surg. 2013; 21(1):55-6. Available from: https://www. commonly supplied by branches of the ulnar ar- ncbi.nlm.nih.gov/pmc/articles/PMC3891100/ tery, followed by branches of the brachial artery. 2. Yammine K. Clinical prevalence of palmaris longus agenesis: Branches of the median nerve supply innervation [1]. a systematic review and meta-analysis. Clin Anat 2013; 26(6):709-18. Available from: https://www.ncbi.nlm.nih.gov/ In the present study the PL was innervated by bran- pubmed/23825029 ches of the median nerve in the proximal third of 3. Ioannis D, Anastasios K, Konstantinos N, Lazaros K, Georgios the forearm. The Acc PL muscle passed superficial to N. Palmaris Longus Muscle’s Prevalence in Different Nations the ulnar artery and ulnar nerve, and was supplied and Interesting Anatomical Variations: Review of the Literature. by the deep branch of the ulnar nerve. Journal of Clinical Medicine Research. 2015; 7(11):825-30. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/ PMC4596262/pdf/jocmr-07-825.pdf

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