Overview
The metacarpus (ossa metacarpalia) is made of five metacarpal bones, numbered I (medial) to V (lateral). The cat is digitigrade: it stands on its digits only, with the metacarpus nearly vertical and raised off the ground, which functionally lengthens the limb.
Key features
- Metacarpal I: short, carries the first digit (dewclaw), which does not touch the ground.
- Metacarpals II to V: long and parallel; III and IV are the longest and most central and bear most of the load.
- Base: the proximal end, which articulates with the distal carpal bones and with neighbouring metacarpals.
- Head: rounded distal end with a sagittal ridge, articulating with the proximal phalanx. On its palmar side lie two proximal sesamoid bones per digit, in the tendons of the interosseous muscles.
- Metacarpal pad: a single, three-lobed pad lying palmar to the metacarpophalangeal joints.
Clinical relevance
- Metacarpal fractures: after trauma and crushing injuries; when one or two bones are involved they are often managed with a splint, while fractures of the central metacarpals or of several bones may need fixation.
- Polydactyly: extra digits, mainly on the medial side of the forepaw, inherited; it may come with extra or fused metacarpal bones.