A unique anatomical variation of flexor digitorum superficialis muscle: a cadaveric case report

J S Nilojan,S Srishankar,N Ketheeswaran,S Udhayakumar

doi:10.4038/slaj.v5i1.136

Abstract

Anatomical variations of the flexor digitorum superficialis (FDS) muscle are uncommon and is related to evolution of muscle from amphibians to human. These variations are of academic interest and should be considered when facing variations in clinical examination, interpreting radiological images and in surgical procedures such as tendon graft. We report a case of unilateral variation of FDS muscle in the forearm with two muscle bellies: superficial and deep which has not been reported before. The humeroulnar and radial origins of the superficial belly united to form a single muscle belly, which divided in the upper part of forearm into two tendons, that passed through carpal tunnel and inserted into the middle phalanges of third and fourth digits. The deep belly originated from medial epicondyle of the humerus next to flexor carpi ulnaris, continued as a short tendon in the upper part of forearm and then formed a second muscle belly in the middle third of the forearm (two muscle bellies separated by an intermediate tendon). In the lower part of forearm deep muscle belly divided into two tendons which traversed the carpal tunnel and was inserted into middle phalanx of second and fifth digits. The report enhances the knowledge on variation of FDS and add a note to understand atypical findings on physical examination and during surgery.

Highlights

The flexor digitorum superficialis (FDS) is an extrinsic muscle of the hand
At the base of the proximal phalanx each tendon splits into 2 slips to allow the passage of flexor digitorum profundus (FDP) and are inserted into the sides of the shaft of middle phalanx of the Udhayakumar S, Nilojan JS, Ketheeswaran N, Srishankar S - A unique Anatomical variation of flexor digitorum superficialis muscle: a cadaveric case report corresponding digit
Elliot el al [10] reviewed the articles reporting the variations of FDS and they classified the variations of FDS into 5 types

Summary

Introduction

The flexor digitorum superficialis (FDS) is an extrinsic muscle of the hand It arises from two heads – humeroulnar and radial, which unite to form a singular muscle belly in the forearm between the superficial and deep muscle groups. The superficial belly had the usual humeroulnar and radial origins, which united to form a single muscle belly It bifurcated at the region of the upper and middle third of forearm, passed below the flexor retinaculum (Fig 1) and inserted into middle phalanx of 3rd and 4th finger (Fig 3). The deep belly bifurcated at middle and lower third of forearm These tendons passed deep to the tendons of superficial belly through carpal tunnel and insert into 2nd and 5th fingers (Fig 3). Udhayakumar S, Nilojan JS, Ketheeswaran N, Srishankar S - A unique Anatomical variation of flexor digitorum superficialis muscle: a cadaveric case report

Discussion

Mainland D