Assistant
Definition
By Gregory R. Waryasz, MD
The trapezium of the musculoskeletal system is characterized by its saddle-like articulation with the base of the thumb metacarpal.
It is part of the upper limb. The trapezium articulates with the 1st and 2nd metacarpals, the scaphoid, and the trapezoid. It consists of bone and cartilage tissue once mature.
Its unique structural features include its being four sided. It is located on the radial aspect of the hand.
The superior surface is has both smooth and rough surfaces.
The inferior surface is saddle shaped.
The dorsal surface is rough.
The palmar surface is narrow and rough. The flexor carpi radialis passes through a groove. The bony attachment for the muscles and the transverse carpal ligament occurs on the palmar surface of the trapezium.
The tubercle of the trapezium is a site where the abductor pollicis brevis muscle occasionally attaches.
The blood supply to the trapezium is through nutrient arteries on each of the non-articular surfaces. There is a strong network of intraosseous anastomoses.
The trapezium ossifies at age 6. The trapezium as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in embryo.
The function of the trapezium is to articulate with the thumb and serve as a potential site for muscle and ligamentous attachments.
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. Arthritis of the carpometacarpal joint is known as basal joint arthritis.
Fracture of the trapezium occurs usually as an avulsion fracture due to the anterior oblique ligament or vertical fracture of the body.
Sprain of the thumb carpometacarpal joint is seen commonly in skiers due to the ski pole and its position during falling.
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 of the basal joint 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.
Wheeless’ Textbook of Orthopaedics: Trapezium (http://www.wheelessonline.com/ortho/trapezium)