Capitate bone
The largest of the carpal bones (sometimes referred to as the os magnum), the capitate sits at the centre of the distal carpal row. A distinctive head shaped bone, it has a protected position in the carpus. The capitate is the site of a number of ligamentous attachments and articulations.
Gross anatomy
Osteology
The capitate sits in a proximo-distal direction, with a waist that is proximal to the transverse midline. The head of the capitate sits proximally into the space allowed by the lunate and scaphoid bones of the proximal carpal bone row. Proximally, the capitate has rounded surface whilst the distal end has a triangular shape with a palmarly directed apex. The dorsal, radial and ulnar surfaces are concave with …show more content…
Variant anatomy
- The capitate usually has a small facet with the base of the fourth metacarpal, which is absent in approximately 14% of wrists
- Accessory bones from residual secondary ossification centres may be mistaken as fractures. Accessory bones may also be the result of trauma or synovial tag ossification.
Radiographic features
Plain film
Due to its protected position in the carpus, fractures of the capitate rarely occur. Fractures may be isolated, but are often associated with perilunate injuries and carpometacarpal fracture dislocation. Fractures may be non-displaced or may demonstrate rotation of the proximal fragment. Proximal pole osteonecrosis may develop.
Naviculocapitate syndrome
- Fracture of the capitate and scaphoid
- Rotated proximal capitate fracture with articular surface displaced
Development
Ossification
The capitate has one ossification centre and is generally the first of the carpal bones to ossify. Although ossification can begin at birth, in the capitate it usually commences in the second month. Several accessory bones may be associated if there is a failure of fusion from additional ossification
The largest of the carpal bones (sometimes referred to as the os magnum), the capitate sits at the centre of the distal carpal row. A distinctive head shaped bone, it has a protected position in the carpus. The capitate is the site of a number of ligamentous attachments and articulations.
Gross anatomy
Osteology
The capitate sits in a proximo-distal direction, with a waist that is proximal to the transverse midline. The head of the capitate sits proximally into the space allowed by the lunate and scaphoid bones of the proximal carpal bone row. Proximally, the capitate has rounded surface whilst the distal end has a triangular shape with a palmarly directed apex. The dorsal, radial and ulnar surfaces are concave with …show more content…
Variant anatomy
- The capitate usually has a small facet with the base of the fourth metacarpal, which is absent in approximately 14% of wrists
- Accessory bones from residual secondary ossification centres may be mistaken as fractures. Accessory bones may also be the result of trauma or synovial tag ossification.
Radiographic features
Plain film
Due to its protected position in the carpus, fractures of the capitate rarely occur. Fractures may be isolated, but are often associated with perilunate injuries and carpometacarpal fracture dislocation. Fractures may be non-displaced or may demonstrate rotation of the proximal fragment. Proximal pole osteonecrosis may develop.
Naviculocapitate syndrome
- Fracture of the capitate and scaphoid
- Rotated proximal capitate fracture with articular surface displaced
Development
Ossification
The capitate has one ossification centre and is generally the first of the carpal bones to ossify. Although ossification can begin at birth, in the capitate it usually commences in the second month. Several accessory bones may be associated if there is a failure of fusion from additional ossification