Carpal Bone Fractures

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Carpal bone fractures make up a significant proportion of injuries to the wrist. The complex bone shape and articulations make diagnosis more difficult and missed injuries more common. This article reviews carpal bone fractures excluding the scaphoid.

Section snippets

Hook fractures

The hook of the hamate protrudes off the hamate into the base of the hypothenar eminence and is palpable 2 cm distal and radial to the pisiform. The relatively thick layer of skin, palmar fibrofatty tissue, and palmaris brevis make palpation more difficult than that of the pisiform. There are multiple attachments to the hook of the hamate including the transverse carpal ligament radially, the pisohamate ligament ulnarly, and the flexor digiti minimi and opponens digiti muscles. The hamate marks

Triquetral fractures

The triquetrum is pyramid shaped. It articulates with the hamate distally, the triangular fibrocartilaginous complex proximally, and the lunate medially. Its palmar surface has an almost completely circular cartilaginous articulation with the pisiform. The triquetrum is well protected by ligamentous attachments on both the dorsal and volar side of the wrist. Triquetral fractures, however, make up the most common carpal bone fracture next to scaphoid fractures [26]. Triquetral fractures can

Pisiform fractures

The pisiform, like the patella, is a sesamoid bone enclosed in the sheath of the flexor carpi ulnaris tendon. It lies on the volar surface and articulates with the triquetrum. The pisiform is the last bone to ossify between ages 8 and 12 years. There may be multiple centers of ossification, giving it a fragmented appearance. This normal appearance must be distinguished from a fracture [32]. Acute pisiform fractures are reported as a source of ulnar-sided wrist pain [7]. If a fracture is

Capitate fractures

The capitate is the largest of the carpal bones and is well protected in the middle column of the wrist where it is surrounded by the other carpal bones and strong wrist ligaments. Fractures of the capitate are relatively rare. In one review, Rand and colleagues [36] found 11 capitate fractures in 978 carpal bone injuries for an incidence of 1.3%. The mechanism of injury of this fracture is debatable. It may involve a direct blow to the wrist, a fall with the wrist in dorsiflexion and ulnar

Lunate fractures

The lunate is shaped like a crescent. Its distal aspect is concave and articulates with the capitate; proximally it articulates with the lunate facet of the distal radius. In a normal situation, the lateral radiographic view shows the capitate, lunate, and distal radius collinear with the wrist in a neutral position. The lunate is integral in the flexion/extension arc and the radial/ulnar deviation arc at both the radiocarpal and midcarpal joints.

Fractures to the lunate are rare. Teisen and

Trapezium fractures

The trapezium forms a double-saddle articulation with the base of the thumb metacarpal allowing motion in two planes—both flexion/extension and abduction/adduction. The volar “beak” ligament from the metacarpal to the trapezium is a key structure in maintaining joint stability and resisting dorsal radial subluxation during key pinch. The trapezium body articulates with the carpal bones. The trapezial ridge is a volar structure that serves as a radial attachment for the transverse carpal

Trapezoid fractures

The trapezoid is tightly positioned between the base of the second metacarpal, capitate, scaphoid, and trapezium with strong intercarpal ligaments. It is wedge shaped, twice as wide dorsally as palmarly, and thereby forms the keystone of the carpal arch. It is the least commonly fractured carpal bone. Because of this position, the more commonly reported injuries include a dorsal dislocation [55]. Axially loading injuries leading to trapezoid fractures can occur [56]. Dislocations can be treated

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      Shear forces from taut flexor tendons during power grip contribute to the fracture and displacement along with direct compression.16 Hamate body fractures occur with high-energy axial load to the fourth and fifth digits, and can occur as a carpometacarpal fracture-dislocation.17,35 In the athlete, these can occur with a direct fall causing an axial load at the fourth and fifth carpometacarpal joints.

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