Bones Of Hand- Metacarpal
BONES OF HAND
The hand consists of:
- Carpal bones at wrist
- Metacarpal bones in the palm
- Phlangeal bones in the digits
- The metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm.
- Metacarpal bones are miniature long bones.
- Five in number and are numbered from lateral to medial side.
- Each metacarpal possesses a diaphysis and a single epiphysis (unique property among long bones as most of the long bones have two epiphysis).
- The epiphysis of all metacarpals are directed towards the head, except in the first where it is located towards the base.
- Heads of metacarpals articulate with proximal phalanges forming MP joints (Knuckles).
- 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).
- Body– The body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces: medial, lateral, and dorsal.
- Base– The base (basis) or carpal extremity is of a cuboidal form, and broader behind than in front.
- It articulates with the carpal bones and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.
- Head– The head (caput) or digital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side
- It articulates with the proximal phalanx.
- It is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.
- On either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal joint.
- the first with the trapezium;
- the second with the trapezium, trapezoid, capitate and third metacarpal;
- the third with the capitate and second and fourth metacarpals;
- the fourth with the capitate, hamate, and third and fifth metacarpals;
- and the fifth with the hamate and fourth metacarpal;
- 1st carpometacarpal joint is Saddle.
- Normal metacarpal index is 5.4 to 7.9.
- Short 4th metacarpal is a feature of Pseudohypoparathyroidism.
- Proximal interphalangeal, distal interphalangeal & 1st carpometacarpal joint involvement and sparing of wrist is a feature of Osteoarthritis.
- Bennett’s fracture is fracture dislocation of base of 1st metacarpal.
- Webbing of neck, increased carrying angle, low posterior hair line and short fourth metacarpal are characteristics of Turner syndrome.
- All the metacarpals in the hand have one epiphysis per bone which is in the head of the bone except the thumb, where it is in the base.
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