Learning Objectives
By the end of this topic, students should be able to:
- Identify the three groups of bones of the hand.
- Name and classify the carpal bones into proximal and distal rows.
- Describe the articulations of the carpal, metacarpal, and phalangeal bones.
- Explain the structure and function of the carpal tunnel.
- Recognize common clinical conditions affecting the hand bones, including scaphoid and metacarpal fractures.
Overview
The bones of the hand provide structural support and enable fine, coordinated movements. They are classified into three groups:
- Carpal bones (proximal): Eight irregular bones forming the wrist.
- Metacarpals: Five long bones forming the palm, each associated with a digit.
- Phalanges (distal): The bones of the fingers and thumb. The thumb has two phalanges, while the remaining digits have three.
This section reviews the anatomy, articulations, and clinical relevance of the bones of the hand.
Carpal Bones
The carpal bones are arranged in two rows: proximal and distal.
Proximal row
- Scaphoid
- Lunate
- Triquetrum
- Pisiform (a sesamoid bone within the flexor carpi ulnaris tendon)
Distal row
- Trapezium
- Trapezoid
- Capitate
- Hamate (with the palmar hook of hamate)
The scaphoid and lunate articulate with the radius to form the radiocarpal joint. The distal row articulates with the metacarpals at the carpometacarpal joints.
Together, the carpal bones form a concave arch. The flexor retinaculum spans this arch, forming the carpal tunnel, which transmits tendons, the median nerve, and vessels into the palm.
Clinical Relevance: Scaphoid Fracture
The scaphoid is the most commonly fractured carpal bone, usually due to a fall on an outstretched hand (FOOSH).
- Presents with anatomical snuffbox tenderness
- Prone to avascular necrosis because its blood supply runs from distal to proximal
- Untreated fractures may lead to wrist osteoarthritis
Metacarpal Bones
The metacarpals connect the wrist to the fingers. They articulate proximally with the carpals and distally with the proximal phalanges.
| Metacarpal | Digit |
|---|---|
| I | Thumb |
| II | Index |
| III | Middle |
| IV | Ring |
| V | Little |
Each metacarpal has a base, shaft, and head and provides attachment for the interossei muscles.
Clinical Relevance: Metacarpal Fractures
- Boxer’s fracture: Neck of the 5th metacarpal; caused by punching a hard object.
- Bennett’s fracture: Base of the 1st metacarpal; caused by thumb hyperabduction and involves the carpometacarpal joint.
Phalanges
The phalanges form the digits.
- Thumb: proximal and distal phalanges
- Other digits: proximal, middle, and distal phalanges
Each phalanx consists of a base, shaft, and head.
