Bilateral Congenital Absence of Small Finger Flexor Digitorum Superficialis Tendons in a Trauma Patient.

The flexor digitorum superficialis (FDS) is the only muscle in the intermediate layer of the flexor compartment of the forearm. Its main function is flexion of the proximal interphalangeal (IP) joint. Variations of the FDS are common, and knowledge of these variations is necessary for hand surgeons because the little finger tendon of the FDS is commonly used in hand reconstruction surgery. Here we present a case of bilateral absence of the little finger tendon of the FDS in an 11-year-old Hispanic female trauma patient presenting to the Emergency Department with multiple traumatic injuries including bilateral hand lacerations sustained in a motor vehicle accident. On physical examination, flexion of the IP joint of the thumb, and metacarpal phalangeal, proximal IP, and distal IP joints of the little finger were absent bilaterally. In the operating theater, the lacerations were extended to evaluate the status of the tendons of the FDS and flexor digitorum profundus (FDP). On the right, a complete transection of the FDP tendons to the ring and little fingers were found and repaired. Upon further exploration, the FDS tendon to the ring finger was identified and repaired, whereas the little finger tendon was found to be absent. On the left, the FPL tendon was identified and repaired along with the FDP tendon to the little finger. The FDS was subsequently identified and found to be lacking the tendon to the little finger. Clinically, the absence of the FDS could lead to problems in hand reconstruction surgery and functional testing of the hand.