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In industry and in the home, the hand is the most commonly injured part of the body. Disorders of the hand rarely jeopardize life but can significantly affect the ability to function.
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The prime functions of the hand are feeling (sensibility) and grasping (opposition). Sensibility is most important on the radial sides of the index, middle, and ring fingers and on the opposing ulnar side of the thumb, where one must feel and be able to pinch, pick up, and hold objects. The skin on the ulnar side of the small finger and its metacarpal, upon which the hand usually rests, must register the sensations of contact and pain to avoid noxious stimuli such as temperature extremes (burns) and other trauma. In addition, the hands make up a large portion of both motor and somatosensory homunculus.
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Mobility is critical for grasping. The upper extremity is a cantilevered system extending from the shoulder to the fingertips. It must be adaptable to varying rates and kinds of movements in three-dimensional space. The stability of proximal bones and their articulations are essential foundations for good skeletal control distally.
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The specialization of the thumb has allowed humans to have superior aptitudes for defense, work, and dexterity. The thumb has exquisite sensibility and is a highly mobile structure with well-developed adductor and thenar (pronating) musculature, giving the crucial ability of opposition. It is the most important digit of the hand, and every effort must be made to preserve its function.
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The position of function of the upper extremity favors reaching the mouth and perineum and achieves a comfortable, forceful, and unfatiguing grip and pinch. The elbow is held at or near a right angle, the forearm neutral between pronation and supination, and the wrist extended 30 degrees with the fingers flexed to almost meet the opposed (pronated) tip of the thumb (Figure 44–1A), as if one was holding a can of soda. This is the desirable position of the extremity especially in cases of arthrodesis or tenodesis, to allow for a functional extremity.
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If the hand must be immobilized, one should try to keep the ligaments around the joints taut as lax ligaments tend to contract. Hence, in most situations, the position of safety, similar to the position of function, is useful to prevent joint contractures. This features the wrist joint at 30 degrees of extension, metacarpophalangeal (MCP) joints flexed to 90 degrees, and the interphalangeal (IP) joints fully extended. This position keeps the collateral ligaments of the MCP and IP joints taut. In most cases, this is an appropriate position for splinting to avoid long-term stiffness.
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Seldom useful is the position of rest, in which the flexed wrist extends ...