Assistant
Definition
By Gregory R. Waryasz, MD
The trapezoid of the musculoskeletal system is characterized by its resemblance to a trapezium.
It is part of the upper limb. The trapezioid articulates with the 2nd metacarpal, trapezium, capitate, and scaphoid. It consists of bone and cartilage tissue once mature.
Its unique structural features include its wedge shape.
The articulation surface with the scaphoid is quadrilateral, smooth, and concave.
The articulation surface with the second metacarpal is convex from side to side and concave forwards and backwards.
The dorsal and palmar surfaces are rough to allow for ligament attachments.
The capitate articulation surface is concave and smooth.
The trapezoid ossifies at age 7. The trapezoid as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in embryo.
The function of the trapezoid is to articulate with the 2nd metacarpal, trapezium, capitates, and the scaphoid.
Common diseases of the trapezium include arthritis, fracture, and sprain
Arthritis can occur at any of the articulations. Common arthritis types that can occur at these locations include osteoarthritis and rheumatoid arthritis.
Fracture of the trapezoid can occur due to trauma.
Dislocation can occur if there is an axial load transmitted through the second metacarpal. There is associated capsular ligament disruption
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, MRI, bone scan, and CT scan.
It is usually treated with non-operative or operative approaches for fractures. Sprains are usually treated operatively. Arthritis is treated initially with physical therapy, NSAIDs, and steroid injections.
References
Elstrom J, Virkus W, Pankovich (eds), Handbook of Fractures (3rd edition), McGraw Hill, New York, NY, 2006.
Koval K, Zuckerman J (eds), Handbook of Fractures (3rd edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.