Anatomy of the flexor digitorum profundus insertion

To describe the anatomical insertion of the flexor digitorum profundus (FDP) on the distal phalanx.

The FDP insertion to the index, middle, ring, and little fingers were dissected in 10 fresh-frozen cadavers. The FDP tendon was dissected off the volar plate, which was elevated from proximal to distal, before the distal phalanx was disarticulated. The distal phalanx was then inked and the FDP was sharply dissected from bone. The insertion length, width, and distance of the insertion from the joint were measured and the insertion surface area and centroid of the FDP insertion were calculated.

The average insertion length and width were 6.2 mm (range, 5.1-7.0 mm) and 7.9 mm (range, 6.9-8.4 mm), respectively. The average surface area of the distal phalanx occupied by the FDP tendon, for all fingers, was 20% (range, 15%-27%). The average distance from the most proximal insertion to the joint surface was 1.2 mm (range, 0.4-2.1 mm) and the calculated centroid of the FDP insertion from the distal interphalangeal joint was 3.6 mm (range, 2.5-5.1 mm) or approximately 20% of the distal phalangeal length.

These findings may aid anatomical attachment of the FDP tendon in the treatment of zone I injuries.

A better understanding of the anatomy of the FDP insertion may aid proper repair positioning in the treatment of zone I injuries.