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The neck of a metacarpal is a common location for a boxer's fracture, but all parts of the metacarpal bone (including head, body and base) are susceptible to fracture. During their lifetime, 2.5% of individuals will experience at least one metacarpal fracture. Bennett's fracture (base of the thumb) is the most common. [4]
It presents on its base one facet on its superior surface, which is concavo-convex and articulates with the hamate, and one on its radial side, which articulates with the fourth metacarpal. On its ulnar side is a prominent tubercle for the insertion of the tendon of the extensor carpi ulnaris muscle .
The first metacarpal bone is short and thick with a shaft thicker and broader than those of the other metacarpal bones. Its narrow shaft connects its widened base and rounded head; the former consisting of a thick cortical bone surrounding the open medullary canal; the latter two consisting of cancellous bone surrounded by a thin cortical shell.
The metacarpal bone of the index finger has two centres of ossification: a primary centre in the shaft and a secondary centre in the head. This contrasts to the first metacarpal bone where the secondary centre is found in the base. The ossification process begins in the shaft during prenatal life, and in the head between 11th and 22nd months. [4]
It articulates with the third metacarpal bone (the middle finger) and forms the third carpometacarpal joint. The capitate bone is the largest of the carpal bones in the human hand . It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones ; a constricted portion or neck; and ...
The base is small and quadrilateral; its superior surface presents two facets, a large one medially for articulation with the hamate, and a small one laterally for the capitate. On the radial side are two oval facets, for articulation with the third metacarpal; and on the ulnar side a single concave facet, for the fifth metacarpal.
The collateral ligaments originate on depressions on each side of the metacarpal heads dorsal to axis of rotation. From there, they extend obliquely and distally to their insertions onto tubercles at the base of the proximal phalanx. The accessory collateral ligaments originate volar to the collateral ligaments and are inserted on the palmar ...
The Bennett fracture is an oblique intraarticular metacarpal fracture dislocation, caused by an axial force directed against the partially flexed metacarpal. This type of compression along the metacarpal bone is often sustained when a person punches a hard object, such as the skull or tibia of an opponent, or a wall. It can also occur as a ...