Anomalous flexor digitorum superficials and associated anomaly

Objective: To study the anomalous Flexor digitorum superficialis (FDS) muscle and discuss its clinical implications. Method: The anomalous FDS was observed incidentally in the left upper limb of human cadaver during routine dissection. Result: The FDS usually has two bellies but in the present case we observed the existence of three bellies. Interestingly, the Palmaris longus (PL) was also absent. The FDS originated from the usual site i.e. the medial epicondyle of the humerus but had three bellies instead of the normal two. The medial belly ended in a tendon which inserted into the anterior surface of the middle phalanx of the middle finger. The intermediate belly continued as tendon which inserted into the anterior surface of the anterior surface of the middle phalanx of the index finger. The lateral belly continued as a tendon which inserted into the anterior surface of the middle phalanx of the ring and the little finger. Conclusion: The absence of PL may be an accepted fact and the absence of the PL is also not known to cause any significant clinical symptom. The anomalous attachment of FDS tendon may alter the kinematics around the interphalangeal and metacarpophalangeal joints. Supernumerary tendons of the FDS may also be liable for compression beneath the Flexor retinaculum (FR). Knowledge of normal and abnormal anatomy of the FDS muscle may be important for hand surgeons planning tendon transplantation and clinicians diagnosing compressive neuropathies.