Trapezium

Anatomy of the trapezium bone in the human wrist

The trapezium is one of the eight carpal bones located in the wrist. It is situated in the distal row of carpal bones and plays a crucial role in the movement and stability of the thumb. The trapezium is distinguished by its irregular shape and is positioned adjacent to the trapezoid bone, with which it is often compared due to their similar names.

Comparison of the trapezium and trapezoid bones

Anatomy

The trapezium is located on the radial side of the wrist, directly beneath the base of the thumb. It articulates with four bones:

• The scaphoid bone proximally
• The trapezoid bone medially
• The first metacarpal bone distally
• The second metacarpal bone distally

The trapezium has a saddle-shaped articular surface that forms the carpometacarpal joint of the thumb, allowing for a wide range of thumb movements, including opposition, flexion, extension, abduction, and adduction.

Function

The primary function of the trapezium is to facilitate the movement of the thumb. Its unique saddle-shaped surface allows for the thumb's opposable movement, which is essential for grasping and manipulating objects. The trapezium also provides stability to the carpometacarpal joint of the thumb, contributing to the hand's dexterity and strength.

Clinical significance

Injuries or conditions affecting the trapezium can significantly impact hand function. Common issues include:

• Osteoarthritis of the carpometacarpal joint, often referred to as "basal thumb arthritis," which can cause pain and reduced mobility.
• Fractures of the trapezium, which may occur due to trauma or falls.

Treatment for trapezium-related conditions may involve physical therapy, splinting, or surgical intervention, depending on the severity of the condition.

Related pages

• Carpal bones
• Thumb
• Wrist
• Osteoarthritis