Assistant
Definition
By Gregory R. Waryasz, MD
The scaphoid of the musculoskeletal system is characterized by being the floor of the anatomic snuff box. It is the largest bone in the proximal carpal row. It is also known as the navicular bone.
It is part of the upper limb. The scaphoid articulates with the radius proximally, trapezoid and trapezium distally, and the capitates and lunate medially. It consists of bone and cartilage tissue once mature.
Its unique structural features include its being a boat-shaped bone. It is approximately the shape of a medium sized cashew. The scaphoid is 80% covered with articular cartilage. The waist is the area in the middle of the bone.
The superior surface is convex, smooth, and triangular in shape.
The inferior surface is convex, smooth, and triangular in shape.
The dorsal surface is narrow with a rough groove to serve as an attachment site for ligaments.
The volar surface is concave and has a site for the attachment of the transverse carpal ligament and sometimes the abductor pollicis brevis.
The lateral surface is rough and narrow and has an attachment site for the radial collateral ligament.
The medal surface has two articulating facets; lunate articulation, and capitates articulation.
Ligament attachments to the scaphoid include radioscaphocapitate ligament and the dorsal intercarpal ligament.
The scaphoid receives its blood supply from the radial artery. The distal scaphoid is the site where the blood supply enters. Smaller vessels enter at the palmar tubercle.
The scaphoid ossifies at 5 years of age. The scaphoid as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in embryo.
The function of the scaphoid is help with wrist motion. The scaphoid exerts flexion/extension control over the lunate and the distal carpal row.
Common diseases of the scaphoid include arthritis, fracture, avascular necrosis, scaphoid impaction syndrome, and dislocation.
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 scaphoid can occur with trauma.
Dislocation of the scaphoid can occur with trauma.
Avascular necrosis is a condition where the blood supply is compromised to scaphoid.
Scaphoid impaction syndrome is a condition that occurs with repetitive hyperextension activities such as in gymnastics and weight lifting.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, MRI, bone scan, and CT scan.
It is usually treated with internal or external surgical fixation or non-operative approaches for fractures. Dislocations are usually treated operatively. Arthritis is treated initially with physical therapy, NSAIDs, and steroid injections. Scaphoid impaction syndrome is initially treated non-operatively, but may eventually require surgery.
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: Scaphoid/ Scaphoid Fracture (http://www.wheelessonline.com/ortho/scaphoid_scaphoid_fracture)