In a Boxer's Fracture, the injury is most commonly seen at the fourth metacarpal, the "ring" finger, and the fifth metacarpal, the "pinky" finger.
Bony Structures
The hand is composed of:
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14 phalanx bones
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5 metacarpals
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8 metacarpals
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First row (proximal) from medial to lateral
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Scaphoid
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Lunate
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Triquetrum
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Pisiform
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Second row (distal) from medial to lateral
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Trapezium
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Trapezoid
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Capitate
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Hamate
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Metacarpals are classified as long bones. They each have a base, shaft, neck, and head.
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The base of the fourth metacarpal articulates with both the hamate and capitate and the third and fifth metacarpals on the ulnar and radial side respectively.
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The base of the fifth metacarpal articulates with the hamate and the base of the fourth on the ulnar side.
Muscular Attachment
Then hand is capable of
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Flexion, extension, abduction, and adduction of the fingers and thumb
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Opposition and circumduction of the thumb
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Flexion, extension, radial deviation, and ulnar deviation of the wrist
Both serve at important attachment sites for muscles of the hand.
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The fifth metacarpal serves as the attachment site for extensor carpi ulnaris, the fourth interosseous dorsalis, and little finger extensor tendons.
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The fourth metacarpal serves as the origin of the third interossei which assist the lumbricles in adduction and abduction of the digits.
Vasculature
Blood supply to the hand comes from the radial and ulnar arteries and travels to the phalanges via the common digital arteries.
Blood then leaves the phalanges from the dorsal digital veins and moves through the radial vein and the posterior ulnar vein towards the the cephalic and antebrachial veins.
Definition: muscles fully contained within the hand, responsible for fine motor movements. Intrinsic hand muscles are arranged in layers that are divided into thenar, palmar, and hypothenar muscles. They act on the carpometacarpal, metacarpophalangeal, and interphalangeal joints directly or via the extensor tendons. Most thenar intrinsic muscles are innervated by the median nerve; all other intrinsic hand muscles are innervated by the ulnar nerve. (Info Drugs.com) (Image from slideshare.net)
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Definition: muscles that arise outside of, but act on, the structure under consideration. Control gross movements, and produce a forceful grip. For example, flexor digitorum profundus originates on the the body of the ulna, interosseous membrane and deep fascia of the forearm but inserts on base of the distal phalanges of the fingers to provide DIP flexion. (Image from classroom.sdmesa.edu)
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