Bones of the Hand

The bones of the hand form the structural framework of the distal upper limb, enabling a wide range of precise and powerful movements. The hand consists of 27 bones divided into three groups: the carpals (wrist), metacarpals (palm), and phalanges (fingers). These bones work together to provide strength, flexibility, and dexterity for tasks ranging from grasping tools to fine motor skills like writing and typing.

Structure

The hand is organized into three major bone groups:

• Carpal bones: 8 small bones arranged in two rows, forming the wrist.
• Metacarpal bones: 5 long bones forming the palm, numbered I–V from thumb to little finger.
• Phalanges: 14 bones forming the fingers and thumb—3 in each finger and 2 in the thumb.

Carpal Bones

The carpal bones are arranged in a proximal and a distal row:

The scaphoid and lunate articulate with the radius at the wrist joint. The pisiform is a sesamoid bone embedded in the tendon of the flexor carpi ulnaris.

Metacarpals

• Each metacarpal consists of a base (proximal), shaft, and head (distal).
• They articulate proximally with the distal row of carpal bones and distally with the proximal phalanges.
• The first metacarpal (thumb) is shorter and more mobile than the others.

Phalanges

• Each finger has three phalanges: proximal, middle, and distal.
• The thumb has only two: proximal and distal.
• Each phalanx has a base, shaft, and head.

Location

The bones of the hand are located distal to the radius and ulna. The carpals form the wrist and articulate with the forearm bones. The metacarpals form the palm, and the phalanges form the digits.

Function

• Grip and manipulation: The bones provide the structural basis for gripping, holding, and manipulating objects with precision.
• Range of motion: Joints between carpal bones and between metacarpals and phalanges allow fine-tuned movements.
• Force transmission: The bones absorb and transfer mechanical forces during weight-bearing or impact (e.g., falls, pushing).
• Dexterity: Complex arrangement of joints and muscles allows independent finger movement essential for writing, typing, and tool use.

Development

The bones of the hand begin ossifying during the fetal period and continue into adolescence:

• Carpals: Each carpal bone ossifies from a single center after birth, beginning with the capitate and hamate (1–6 months of age). The pisiform ossifies last, around 9–12 years.
• Metacarpals and phalanges: Ossify from a primary shaft center and secondary epiphysis, which fuse by late adolescence.

Clinical Significance

• Scaphoid fracture: Most common carpal fracture; risk of avascular necrosis due to poor blood supply.
• Carpal tunnel syndrome: Compression of the median nerve under the transverse carpal ligament, affecting hand sensation and function.
• Boxer's fracture: Fracture of the neck of the 5th metacarpal, often from punching a hard object.
• Dislocations: Can occur at the carpometacarpal or metacarpophalangeal joints, especially in trauma.
• Osteoarthritis: Common in elderly patients, especially at the thumb base (first carpometacarpal joint).