Assistant
Definition
By Gregory R. Waryasz, MD
The hamate of the musculoskeletal system is characterized by its being wedge shaped bone with a hook.
It is part of the upper limb. The hamate articulates with the lunate, 4th and 5th metacarpals, the triquetrum, and capitate. It consists of bone and cartilage tissue once mature.
Its unique structural features include its wedge shape and its hook like projection.
The articulation surface with the lunate is narrow, convex, and smooth.
The metacarpal articulation surface has concave facets separated by a ridge.
The dorsal surface is triangular shaped and rough to accommodate ligamentous attachments.
The volar surface has the hook-like process known as the hamulus. The hamulus is the site of attachment for the transverse carpal ligament, flexor digiti minimi, and the opponens digiti minimi.
The triquetrum articulation surface has an oblong facet.
The capitate articulation surface is smooth but this side of the bone has rough locations for ligament attachments.
Blood supply to the hamate is from two sites; hook radial base and the hook ulnar tip.
The hamate ossifies at 1 to 2 years. The hamate as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in embryo.
The function of the hamate is to articulate with carpal bones and metacarpals. It also has a function to serve as muscular and ligament attachment points. It helps to form Guyon’s Canal where the ulnar artery and nerve are protected.
Common diseases of the hamate includes arthritis and fracture.
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 hamate can occur due to trauma. It is usually a hairline fracture. The body of the hamate fractures with trauma. The hook of the hamate is common to athletes who are struck on the palm of the hand. Fractures of the hook of the hamate can cause neurovascular injury to the ulnar nerve or ulnar artery in Guyon’s canal.
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 to attain normal anatomic relationships. 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.
Wheeless’ Textbook of Orthopaedics: Hamate (http://www.wheelessonline.com/ortho/hamate)