Multiple digit camptodactyly caused by anomalous ulnar sided flexor digitorum superficialis insertions

We report an anomalous insertion of the flexor digitorum superficialis (FDS) tendon causing multiple digit camptodactyly. The abnormal tendon was present in the ring and middle fingers, passing from the FDS tendon (proximal to the proximal interphalangeal-PIP-joint) to the extensor expansion (distal to the PIP joint). It was present on the ulnar aspect only, with no corresponding structure on the radial side. Division of the anomalous insertion corrected the fixed flexion deformity at the PIP joint. This anomaly has not been reported in clinical or cadaveric studies and could have been overlooked if a volar approach had been used.