UNIQUE VARIATION OF FLEXOR DIGITORUM SUPERFICIALIS TO THE LITTLE FINGER - A CASE REPORT

Mohamed Thuslima, Dhivyalakshmi Gnanasekaran* and Raveendranath Veeramani

ABSTRACT

Flexor digitorum superficialis (FDS) is the largest of the superficial flexors of the forearm. It arises by humero ulnar and radial heads. The muscle usually separates into two strata. The superficial stratum joined laterally by the radial head, divides into two tendons for the middle and ring finger and the deep stratum for the index and little finger. Distal to the carpal tunnel the four tendons diverge and insert into the middle phalanx. During routine dissection, a unique variation of FDS was identified. The deep stratum divided very proximally into two muscle bellies and then ends in two tendons for the little finger and index finger. The tendon to the little finger (FDS V) presented an intermediate muscle belly at the distal forearm that was connected to the superficial stratum of FDS on its radial side. A thin tendinous slip of communication was noted between the proximal tendon of FDS V and the tendon of flexor digitorum profundus muscle, which merged with the later at the level of the middle of the forearm. Phylogenitically, these variations are considered to be due to either retrogressive remnants of connection between two strata or progressive occasional separation of the individual muscle belly. This additional tendon slips can be used as a separate motor unit in tendon transplant surgeries. The anomalous tendinous communication between flexor digitorum superficialis and flexor digitorum profundus tendon may limit finger independence and can produce restrictive flexor tenosynovitis. Surgeons should be aware of such variations to differentiate, diagnose and treat various disease conditions of distal forearm and hand.

Keywords: Flexor digitorum superficialis, flexor of forearm, flexor digitorum profundus, tendon graft, hand grip.