Mittelhand

Mittelhand refers to the metacarpus, the five long bones of the hand located between the carpal bones of the wrist and the proximal phalanges of the fingers. They are labeled I to V from the thumb side. Each metacarpal consists of a proximal base that articulates with the distal carpal row, a shaft, and a distal head that forms the metacarpophalangeal joint with the proximal phalanx. The bases connect with the carpal bones at carpometacarpal joints, and the heads form the knuckles at the metacarpophalangeal joints. The first metacarpal (thumb) is particularly robust and oriented to enable opposition; the second through fifth metacarpals contribute to the curved arch of the palm and hand grip. Small intermetacarpal joints connect adjacent metacarpals and allow limited movement.

Functionally, the Mittelhand bones transfer loads from the fingers to the wrist and forearm, providing the rigid framework of the palm. They act as levers for finger flexors and extensors and serve as attachment points for intrinsic hand muscles, including the interossei and lumbricals, as well as for tendons of extrinsic muscles. The metacarpals, together with the carpals, enable a wide range of grip and precision movements.

Clinical significance commonly involves metacarpal fractures and injuries. Fractures of the neck or shaft of metacarpals are frequent, with boxer's fracture referring to fractures of the neck of the fourth or fifth metacarpal. Carpometacarpal or metacarpophalangeal joint injuries, dislocations, and osteoarthritis at the thumb base are also clinically relevant. Understanding the Mittelhand is fundamental to describing hand anatomy, biomechanics, and related pathologies.