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The third metacarpal bone (metacarpal bone of the middle finger) is a little smaller than the second.. The dorsal aspect of its base presents on its radial side a pyramidal eminence, the styloid process, which extends upward behind the capitate; immediately distal to this is a rough surface for the attachment of the extensor carpi radialis brevis muscle.
The ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent. [1] Each metacarpal bone consists of a body or shaft, and two extremities; the head at the distal or digital end (near the fingers), and the base at the proximal or carpal end (close to the wrist).
intra articular comminuted fracture of base of first metacarpal: axial load along the metacarpal causing splitting of the proximal articular surface: Rolando's fracture at Wheeless' Textbook of Orthopaedics online Runner's fracture: Running: stress fracture of distal fibula 3–8 cm above the lateral malleolus: repeated axial stress on fibula
The distal surface is divided by two ridges into three facets, for articulation with the second, third, and fourth metacarpal bones, that for the third being the largest. [1] The dorsal surface is broad and rough. [1] The palmar surface is narrow, rounded, and rough, for the attachment of ligaments and a part of the adductor pollicis muscle. [1]
Primitively, each of the distal bones appears to have articulated with a single metacarpal. However, the vast majority of later vertebrates , including modern amphibians , have undergone varying degrees of loss and fusion of these primitive bones, resulting in a smaller number of carpals.
The distal row consisted of five elements sitting above the five metatarsals, which are denoted as distal carpals 1–5. The middle row is represented by a single element, the centrale. [27] [28] carpometacarpus The carpometacarpus is a bony element of the hand consisting of the fused carpals and metacarpals.
The distal part of the palmar ligament, called the palmar plate, is 2 to 3 millimetres (0.079 to 0.118 in) thick and has a fibrocartilaginous structure. The presence of chondroitin and keratan sulfate in the dorsal and palmar plates is important in resisting compression forces against the condyles of the proximal phalanx.
The third metatarsal is analogous to the third metacarpal bone in the hand [1] Like the four other metatarsal bones, it can be divided into three part: base, body and head. The base is the part closest to the ankle and the head is closest to the toes. The narrowed part in the middle is referred to as the body of the bone.