EPICONDYLO HAMARIS TRANSVERSALIS MUSCLE

1AMAR JAYANTHI A

&

2ARUNKUMAR K G

1Additional Professor of Anatomy, Government Medical College, Thrissur, Kerala, India.

2Junior Resident, Government Medical College, Thrissur, Kerala, India

ABSTRACT

During routine dissection, an accessory superficial muscle was detected in the right forearm of a female adult

cadaver. The accessory muscle attached to medial epicondyle, flexor retinaculum and hook of hamate was medial to Palmaris

longus. This variant muscle resembled a reverse Palmaris longus with distal attachment not extending to the palm. Variant

muscles are usually over looked and form incidental findings during surgery or dissection. Variant muscles with long tendons

can be used for tendon grafts and tendon transfer without producing any functional deformity.

KEY WORDS: Accessory Muscle, Hook of Hamate, Transversalis Muscle, Medial Epicondyle

INTRODUCTION

Different variations of flexor muscles of forearm have been reported in literature. The muscles that vary most are

muscles that are either appearing in the species and muscles that are disappearing in evolution [1]. Reports on supernumerary

and accessory muscles in forearm dates back to 1813 by Gantzer [2]. A variant muscle that arouse as a tendon from common

flexor origin and inserted into the flexor retinaculum was discovered in the right forearm of an adult female cadaver. The long

tendon and small muscle belly resembled that of Palmaris longus but differed from it in the case of insertion at the carpal bone.

CASE REPORT

During routine dissection of an embalmed adult female cadaver in the department of Anatomy, Government Medical

College, Thrissur, Kerala State, India, we came across a superficial muscle having fleshy fibers in the distal one third of right

forearm. The variant muscle was anterior to all the other forearm flexor muscles. The superficial muscles namely

brachioradialis, pronator teres, flexor carpi radialis, palmaris longus and flexor carpi ulnaris showed usual topography. In

addition to the usual flexor muscles a spindle shaped muscle with tendino – musculo – tendinous attachment from medial

epicondyle to the flexor retinaculum was observed (figure.1).

Figure 1: Illustration Shows the Variant Muscle Attached to Medial Epicondyle of Humerus and Hook of Hamate.

Palmaris Longus is Seen Lateral to the Variant Muscle.

International Journal of Medicine and

Pharmaceutical Sciences (IJMPS)

ISSN 2250-0049c

Vol.2, Issue 3, Dec 2012 9-12

© TJPRC Pvt. Ltd.,

10 Amar Jayanthi A & Arunkum K G

The muscle had its origin from medial epicondyle as a long tendon that changed into a spindle shaped muscle belly in

the middle of forearm and inserted into the proximal part of flexor retinaculum at the ulnar end by a slender tendon

encroaching onto the hook of hamate. The muscular portion was flattened antero posteriorly and was superficial to ulnar artery.

The muscle was lying medial to the tendon of palmaris longus and lateral to flexor carpi ulnaris with ulnar nerve and artery

between them at distal end of forearm. The ulnar artery was tortuous near the wrist. The hypothenar muscles were cut and

removed to expose the flexor retinaculum where the distal attachment was (figure 2).

Figure 2: Illustration Shows the Variant Muscle with Distal Attachment to Hook of Hamate. The Hypothenar Muscles

Were Removed to Expose Flexor Retinaculum and the Variant Muscle Is Picked up to Show its Insertion.

Ulnar artery and nerve were seen medial to the variant muscle and median nerve lateral to it. Nervous and arterial

supply to the variant muscle could not be traced.

DISCUSSIONS

Palmaris longus is a fusiform muscle attached to medial epicondyle and inserted through flexor retinaculum and

palmar aponeurosis into skin and fascia of palm. Palmaris longus is one of the most variable muscles of human body.

Common variations being, complete absence, duplication, triplication, variable location and accessory slips [3]. In addition

variations listed by Phillip E Wright include double Palmaris longus tendon, multiple insertions and associated aberrant

muscle[4]. Jeffery described anomalous muscle in the lower forearm in the absence of Palmaris longus[5]. A variant of

Palmaris longus with tendinous origin and thick muscle belly towards insertion was reported in a male cadaver by Oommen

[6].

The variant muscle reported here is not a substitute for any flexors of forearm. This variant muscle may appear similar

to variations published earlier but it differs from the rest due to shape of the muscle being spindle, antero- posteriorly flattened

and present in addition to Palmaris longus. Muscles derive their names from situation, direction of fibers, points of attachment,

shape ,uses and number of their division. This variant muscle mimicking a reversed Palmaris longus with long tendon and not

entering palm may be better named “epicondylo hamaris transversalis ” to denote the relationship to medial epicondyle of

humerus and hamate bone and the muscle fiber orientation.

The functional role of this muscle is at doubt as the fibers are oriented transversely. Accessory muscles and tendons

are surgically noteworthy. Since distally placed and superficial to other structures, where usually only tendons exist, over use

of this muscle can lead to muscle hypertrophy, median nerve compression may cause apparent carpal tunnel syndrome,

Epicondylo Hamaris Transversalis Muscle 11

compression of ulnar artery causes sluggish flow leading to thrombosis and Guyon’s syndrome. Three cases of distal belly of

Palmaris longus muscle compressing median nerve between itself and the underlying tendons was reported by KM Backhouse

and D Churchill Davidson where the usual pattern of Palmaris longus was absent [7]. Median nerve compression in the wrist

by anomalous Palmaris profundus muscle was reported by M F Fatah [8]. Careful evaluation of fibro osseous tunnels for an

accessory muscle may help to identify such a muscle as a causative factor in compression neuropathies in relation to carpal

tunnel and Guyon canal [9].

In primates and other mammals (pigs, foxes and marmots) the accessory heads of the flexor muscles are described as

a muscle belly that connects the origin of the flexor digitorum superficialis with the deep flexor muscles [2]. The accessory

muscle of forearm described in the present case arouse from medial epicondyle as a long tendon and inserted to carpal bone

again by a tendon with intermediary muscle belly. Limb myogenesis occurs by migration, proliferation and differentiation of

mesenchymal muscle precursor cells into the limb anlagen where they form individual muscles [10]. The embryological basis

for this variant muscle could be due to persistence of ventral muscle mass that are disappearing in evolution or could be due to

an unusual migration of myoblast during morphogenesis.

CONCLUSIONS

Majority of variant muscles are asymptomatic and form incidental findings during surgery, imaging or dissection.

However variant muscles may result in compression neuropathies or present as a palpable mass. We would like to state that,

the observations made by us in the present case will supplement our knowledge of muscular variations of use in forearm and

hand surgery.

ACKNOWLEDGEMENTS

The authors wish to thank the 30th

Osler students for their support and encouragement and Mr. Asok kumar T K,

Artist of Anatomy department for the illustrations.

REFERENCES

1. John V Basmajian & Charles E Slonecker. Grant’s method of Anatomy. 11th

Edn B I Waverly Rt Ltd. Waverly. 23 -

24.

2. Vollala V R et al [2008] Multiple accessory structures in the upper limb of a single cadaver-case report. Singapore

Med J ; 49(9)e 254-256.

3. Reimann A F et al.[1944] Palmaris longus muscle and tendon. A study of 1600 extremities. Anat Rec ; 89: 495 – 505.

4. Philip E Wright II. Flexor and extensor tendon injuries. Campell’s Operative Orthopaedics. 11th

Ed, Vol 4, 3886.

5. Engine Ciftcioglu et al.[2011] Accessory muscle in the forearm. Clinical and embryological approach. Anat Cell Biol

2011; 144: 160-163.

6. Oommen A [2002] Palmaris longus – Upside Down. JASI. 2002; vol 51.No.2: 232-233.

7. K M Back house and D Churchill Davidson. Hand. Feb 1975; vol 7 issue 1: 22-24.

12 Amar Jayanthi A & Arunkum K G

8. M F Fatah.[1984] Palmaris profundus of Frohse and Frankel in association with carpal tunnel syndrome. Journal of

hand surgery: British and European Volume; vol 9 issue 2: 142-144.

9. Paul A Sookur et al [2008]. Accessory muscles. Anatomy, Symptoms and Radiologic Evaluation. Radiographics; Vol

28 No.2: 481-495.

10. Bodo Christ et al [2002]. Limb muscle development. Int. J. Dev. Biol; 46: 905-914.