![]() Thumb metacarpal shaft fractures are treated similarly to the other four metacarpals. This fracture is similar to the Bennett's fracture, but with more comminution and shortening it is, therefore, a more severe injury. This fracture results in shortening and deformation of the thumb, due to lack of support from the bone and shear pull from the abductor pollicis longus.Īnother notable thumb injury is the Rolando's fracture (Figure 6), one with T or Y shaped intra-articular fracture line at the base of the thumb metacarpal. Metacarpal head fractures are rare and usually require surgical intervention.Ī notable thumb injury is the Bennett's fracture (Figure 5), a partial articular fracture of the first metacarpal base. Such a fracture seen in the 5th (or rarely, the 4th) metacarpal neck is called a "boxer’s fracture" (Figure 4). Metacarpal neck fractures are the most common type of metacarpal fracture. The pull of the interossei muscles and flexor tendons can deform shaft fractures leading to metacarpal shortening or angulation. These present respectively as transverse fractures (with comminution at times) and spiral fractures. Shaft fractures are most frequently the result of direct trauma, axial loading, or twisting injury. Metacarpal base fractures usually occur as a result of significant axial load to a flexed hand as seen in clenched fist injuries. Range of motion tests should be conducted, and the hand should be assessed for sensory changes to determine possible nerve damage.įractures within each of the four regions of the metacarpal bone – base (Figure 2), shaft (Figure 3), neck, and head – are considered distinctly. In a normal flexed hand, the fingertips should align and point towards the scaphoid tubercle on the radial volar aspect of the wrist. ![]() Physical examination of the hand may reveal deformities, decreased grip strength, and possible finger misalignment. Findings include pain (most intense over fracture site), oedema, a shortened finger or finger deformity (such as depressed or missing knuckle), and bruising. At times, a crush mechanism is responsible. Metacarpal fractures usually occur after a fistfight, car accident, or fall. The looser attachments of the fourth and fifth metacarpals allow them to oppose the thumb. The second and third metacarpals are more rigidly fixed upon the corresponding carpal bones than the fourth and fifth metacarpals. The first metacarpal is shorter and wider than the other metacarpals and has a more extreme angulation with the carpus. The head of the metacarpal receives its own blood supply from the collateral ligaments this arrangement predisposes the head to possible avascular necrosis with a ligament injury, as the ligament injury may disrupt perfusion. The dorsum of the head accommodates the extensor tendons while the palmar surface has a ridge for the flexor tendons. The metacarpal head articulates with the proximal phalanx of each finger, with tubercles on each side providing attachment for the collateral ligaments. The metacarpal neck lies just proximal to the head, distal to the shaft. The extensor tendons lie atop the flat dorsum of the metacarpal shaft. This attachment, along with the extensor and flexor muscles crossing (but not attaching to the metacarpal), produces the main deforming force that may displace shaft fractures. The medial and lateral surfaces provide attachment for the interossei muscles. ![]() There is a medial, lateral, and dorsal surface on the metacarpal shaft. The body (or shaft) of the metacarpal is concave with respect to the palmar surface. The metacarpal base is cuboidal in shape, and ligaments provide articulations between the metacarpal bones and the carpus at the carpometacarpal (“CMC”) joint. From radial to ulnar, the bones are numbered one (thumb) through five (small finger) and consist of a shaft, base, and head. The metacarpals consist of five tubular bones that articulate proximally with the carpus and distally with the phalanges (Figure 1). Figure 1: The 5 metacarpal bones are shown in red.
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