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Middle Phalanges (Hand)

phalanges mediae manus

The four middle phalanges (absent in the thumb) articulate with the proximal phalanges above and the distal phalanges below at the interphalangeal joints, carrying the insertions of the flexor and extensor digitorum tendons.

Anatomical Data

Structure & Landmarks

Articulations	Proximal phalanges at the PIP joints Distal phalanges at the DIP joints
Landmarks	Base with central ridge Shaft Head (bicondylar) FDS insertion site
Ossification	Endochondral ossification with proximal epiphyses.

Clinical Relevance

Clinical Notes

Middle phalanx fractures are commonly associated with PIP joint dislocations and volar plate injuries. The attachment of the FDS at the sides of the middle phalanx and the central slip of the extensor mechanism at the base make the fracture displacement pattern complex and dependent on fracture level relative to these insertions. Condylar fractures of the middle phalanx producing lateral instability at the DIP joint require fixation to prevent permanent deformity.

Pathology

Common Injuries & Conditions

Volar Plate Avulsion Fracture

Hyperextension of the PIP joint, as in ball sports, avulses a fragment from the palmar base of the middle phalanx.

PIP Joint Fracture-Dislocation

Larger fractures of the base of the middle phalanx allow dorsal subluxation of the joint and often need surgical stabilisation.

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