Finger Dislocation

Anatomy

In each finger, there are three bones, called phalanges: (1) the distal phalanx, which is located furthest from the wrist; (2) the middle phalanx; and (3) the proximal phalanx. The thumb contains only two phalanges: the proximal and the distal phalanx. Each proximal phalanx is joined to a specific metacarpal bone, one of the five bones that compose the middle part of the hand. Bones are linked to each other in joints: Finger dislocation may involve either the joint between two phalanges, which is called the interphalangeal joint, or the joint between the proximal phalanx and the metacarpal bone, which is called the metacarpophalangeal joint (see Figure 1).

Around the joints, there are ligaments and tendons. These structures stabilize the joint, holding the bones together, and allow the muscles to perform their movements. Ligaments are bundles of [Page 524]fibrous tissue that connect the extremities of different bones. In the hand, each interphalangeal and metacarpophalangeal joint is supported by the volar plate, which forms the floor of the joint, and two collateral ligaments. Tendons are ropelike structures that attach the muscle to the ends of one or more bones. Also, tendons lend further support to joints.

Figure 1 Finger Dislocations: A = Metacarpophalangeal Joint; B = Interphalangeal Joint

Injuries that cause bone misalignment can also provoke damage to ligaments and tendons. In fact, when bones lose their normal joint position, ligaments may disconnect from their attachment or tear, and tendons may suffer strains and tears. These injuries can cause further joint instability. Moreover, other soft tissues that surround the dislocation site may suffer damage, among them the muscles, periosteum (the tissue that covers the bones), nerves, blood vessels, and connective tissues.

Causes

Sports are among the most common causes of dislocations. A finger dislocation can result from falls and all accidents in which fingers are trapped between objects (e.g., equipment, such as helmets and pads), twisted sideways, and/or forced to hyperextension or hyperflexion. Hyperextension is a movement that extends the angle between the bones of a joint, so that this angle becomes greater than normal. For instance, this may occur when an athlete tries to catch a ball with his or her finger-tips. On the contrary, hyperflexion is a movement that decreases the angle between the bones of a joint, so that this angle becomes smaller than normal. These events occur frequently in sports and especially in martial sports. Dislocations may occur in predisposed athletes even in the absence of severe trauma: Such a predisposition is shown by participants whose ligaments are looser than normal—for instance, those who suffer from congenital ligamentous laxity.

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