- Tuft or ungual tuberosity
Distal phalanges of the middle and ring finger are similar in length.
It is followed by index and little finger. Except for little finger, width of all the disal phalanges is same.
On the dorsal aspect base flares out dorsally and centrally creating a ridge that separates the articular surface from the shaft.
Image modified from AO Foundation
The shaft is wide proximally and narrows distally with narrowest portion being just proximal to the tuft. The dosral portion of the shaft is slightly convex and rounded and it is slightly concave on palmar side. Medial and lateral surfaces are rounded.
Tuft is the terminal thick roughened crescent shaped wide portion of the distal phalanx.The tuft provides for attachement of septae that support, stabilize, and anchor the pulp of the digit to distal phalanx
A volar tubercle is present on volar side and two lateral tubercles [one on radial and one on ulnar side.
Ligaments pass from the distal margin of the widened lateral base to the expanded proximal margins of the tuft. The small branches of the proper digital artery that supply the dorsal arcade just proximal to the nail fold pass under these ligaments very close to the base of the shaft of the distal phalanx.
Digital pulp is a honeycomb structure of fibrous septae containing pockets of fat in each compartment. The proximal part of the pulp is thicker and more mobile than the distal pulp. Tuft is the anchoring point of the architecture of pulp.
The dorsal surface of the distal phalanx is the direct support for the germinal matrix and sterile matrix of the nail. The bone volarly and the nail plate dorsally create a three layered sandwich with the matrix in the middle.
Anatomy of Distal Interphalangeal Joint
Distal interphalangeal joint is a bicondylar ginglymus joint.
There are two types of collateral ligaments –
– The accessory collateral ligaments attach distally to the lateral margins of the volar plate.Distal interphalangeal joint stability is maintained by articular congruity, the dynamic balance of flexor and extensor tendons and ligaments.
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