section: 1/5 page: 1/8 next

1Principles

The distal phalanx is divided into three anatomical parts: most proximally, the metaphysis, followed by the diaphysis ...

Anatomy

The distal phalanx is divided into three anatomical parts: most proximally, the metaphysis, followed by the diaphysis (“waist”), and finally the ungual tuberosity (“tuft”).

The base of the distal phalanx has a prominent crest on the dorsal aspect with the insertion of the terminal extensor tendon. The tendon is adherent to the joint capsule.
On the palmar surface is the insertion of the flexor digitorum profundus tendon. This is adherent to the volar plate and to the periosteum.
The flexor tendon occupies the whole width of the base of the distal phalanx. It is made up of 2 different fibers. The superficial fibers attach to the lateral aspects of the phalanx. The deep fibers run centrally and attach more distal in the palmar aspect of the phalanx.
The volar plate is very flexible, allowing hyperextension of the DIP joint to allow pulp-to-pulp pinching, which is unique to humans. This flexibility is also facilitated by the absence of check reins, which might be attached to the middle phalanx.