Trapezoid bone

Trapezoid Bone

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Palmar view of the trapezoid bone in the left hand

The trapezoid bone, also known as the os trapezoideum, is one of the eight carpal bones in the human wrist. It is situated in the distal row of the carpal bones and is the smallest bone in this row. The trapezoid bone plays a crucial role in the complex movements of the wrist and hand, contributing to the dexterity and functionality of the human hand.

Anatomy

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Illustration showing the position of the trapezoid bone

The trapezoid bone is located between the trapezium bone laterally and the capitate bone medially. It articulates with four bones: the second metacarpal bone, the trapezium, the capitate, and the scaphoid bone. The trapezoid bone is characterized by its wedge shape, with the broader end facing dorsally and the narrower end facing palmarly.

Surfaces

The trapezoid bone has six surfaces:

• Dorsal surface: This surface is rough and provides attachment for ligaments.
• Palmar surface: Also rough, it serves as an attachment point for ligaments.
• Lateral surface: Articulates with the trapezium.
• Medial surface: Articulates with the capitate.
• Proximal surface: Articulates with the scaphoid.
• Distal surface: Articulates with the second metacarpal.

Function

The trapezoid bone is integral to the stability and movement of the wrist. It helps in the transmission of forces from the hand to the forearm and allows for the intricate movements necessary for gripping and manipulating objects. The articulation with the second metacarpal is particularly important for the precision grip.

Development

The trapezoid bone ossifies from a single center, which appears between the ages of 4 and 6 years. This ossification process is part of the normal development of the carpal bones, which typically complete ossification by late adolescence.

Clinical Significance

Injuries to the trapezoid bone are rare due to its protected position within the carpal bones. However, fractures can occur, often as a result of direct trauma or severe wrist injuries. Such fractures may require immobilization or surgical intervention depending on the severity.

Images

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Animation of the trapezoid bone in the left hand

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Another animation of the trapezoid bone in the left hand

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Image of the trapezoid bone

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Posterior view of the trapezoid bone

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Diagram showing the trapezoid bone

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Lateral view of the trapezoid bone

Related Pages

• Carpal bones
• Trapezium bone
• Capitate bone
• Scaphoid bone
• Metacarpal bones