Long Middle Phalanx Anatomy

  • The middle phalanges are small long bones of the fingers.
  • The base of the middle phalanx, which is part of the PIP joint, and the distal head, which is part of the DIP joint, are covered with articular cartilage.
  • The middle phalanx has five basic parts: The head or distal epiphysis, the neck or metaphysis, the shaft or diaphysis, the proximal metaphysis, and the base or proximal epiphysis.
  • The concave proximal ends of the middle phalanx articulate with the proximal phalanx.
  • The distal end of the 2nd, 3rd, 4th, and 5th middle phalanges articulate with the base of the 2nd, 3rd, 4th, and 5th distal phalanges.
  • Dorsally the central slip, which part of the extensor hood, inserts into a dorsal tubercle at the base of the middle phalanx.
  • Palmarly the FDS tendon inserts into the palmar aspect of the base of the middle phalanx.
  • Note the middle phalanx of the finger is located in the finger sections (2-5).
Diagrams & Photos
  • Bones of the fingers and hand.
    Bones of the fingers and hand
  • Dorsal anatomic view of the finger bones.
    Dorsal anatomic view of the finger bones.
Key Points
  • The fossae on the radial and ulnar sides of the middle phalanx head are the origin site of the DIP joint collateral ligaments.
  • The head of the middle phalanx has two condyles with a small shallow intercondylar groove.
  • In the growing child there is an epiphyseal plate in the base of the middle phalanx.
  • The middle phalanges of the fingers are displaced during PIP joint dislocations and complex dislocations and remain in their anatomic position during DIP dislocations.
  • Simple stable non-displaced fractures of the phalanges can be treated with splinting while fractures that are unstable due to displacement or comminution may require percutaneous pining or open reduction and internal fixation.
Anatomy References
Anatomic Abbreviations
Hand Surgery Resource Anatomy Diagnostic Guide (Chapter)