The wrist and hand contain numerous small bones, including the carpal bones, a group of eight bones forming the wrist. The trapezium bone is a small, yet important, member of this group.
Where is the Trapezium Bone Located?
The trapezium bone, sometimes referred to as the greater multangular bone, is situated on the radial, or thumb, side of the hand. It is part of the distal row of carpal bones, positioned directly at the base of the thumb. This bone forms connections with several surrounding structures, articulating with the first metacarpal bone of the thumb, the scaphoid bone proximally, and the trapezoid bone medially.
The trapezium has an irregular, four-sided shape, often described as cube-like. Its unique form includes a deep groove and a tubercle on its palmar surface, serving as attachment points for important muscles and ligaments of the hand. Its exact size can vary, but it typically measures around 19-23mm in length and 11-15mm in width and height.
How the Trapezium Bone Functions
The primary role of the trapezium bone lies in forming a specialized joint at the base of the thumb, known as the carpometacarpal (CMC) joint, or trapeziometacarpal joint. This particular joint is distinct from others in the hand due to its saddle shape, allowing the first metacarpal bone to move in multiple directions. This unique configuration provides the thumb with an extensive range of motion.
This exceptional mobility enables the thumb to perform opposition, the ability to touch the tips of the other fingers. Opposition is important for gripping, pinching, and grasping objects, supporting fine motor skills and hand dexterity. The trapezium also anchors various muscles, including the flexor retinaculum and several thenar muscles, which are important for controlling thumb movements.
Common Issues Related to the Trapezium Bone
Despite its robust design, the trapezium bone is susceptible to certain conditions, particularly due to the constant demands placed on the thumb joint. Osteoarthritis is a common issue affecting the carpometacarpal joint, often referred to as thumb basal joint arthritis. This condition results from the gradual degeneration of cartilage within the joint, leading to pain, stiffness, and reduced function. Symptoms typically include a dull aching pain at the base of the thumb, especially with activities like gripping or pinching, along with swelling and a possible clicking or grinding sensation. This type of arthritis is more frequently observed in individuals over the age of forty, and it is more common among women.
The trapezium bone can also sustain fractures, although these are less common than fractures in some other carpal bones. Such fractures often result from direct trauma or axial compression forces, such as falling onto an outstretched hand. While isolated trapezium fractures can occur, they are frequently associated with other injuries in the wrist or hand, including fractures of adjacent bones or dislocations of the carpometacarpal joint. Dislocations of the trapezium itself are rare and usually happen in conjunction with significant high-energy trauma.