The scaphoid (os scaphoideum) is the largest of the proximal row of carpal bones and forms the radial portion of the carpal tunnel. It is important for stability and movement at the wrist and may be fractured after a fall onto a hyperextended hand. Scaphoid fractures may be radiologically occult in the acute setting and may result in avascular necrosis.
The scaphoid is the largest of the proximal row of carpal bones and sits on the radial side of the lunate. It is a boat-shaped bone that is orientated obliquely with its long axis aligned from the medial portion of the distal radius proximally to the articulation of the 1st and 2nd metacarpals distally.
The scaphoid can be divided into proximal and distal poles. The waist (between the two) is the commonest site of scaphoid fracture. The scaphoid tubercle is a bony prominence on the ventral surface of the lateral portion of the distal pole.
The scaphoid articulates with five bones: the radius, trapezoid, trapezium, lunate and capitate.
- proximal surface: radius
- distal surface: laterally with the trapezoid and trapezium; medially with the capitate
- ulnar surface: lunate
Proximally, the smooth convex surface of the scaphoid articulates with the distal radius.
The distal surface is split into two separate articular surfaces by a bony ridge. Radially, it articulates with the trapezoid and trapezium while on the ulnar side, it articulates with the capitate.
The medial surface has a concave appearance and articulates with the lunate.
There are no musculotendinous attachments to the scaphoid bone.
- dorsal surface: dorsal radiocarpal ligament
- radial surface: radial collateral ligament
- scapholunate ligament
- radioscapholunate ligament
- scaphocapitate ligament
The radial artery crosses the dorsal surface of the scaphoid.
The scaphoid forms the radial portion of the carpal tunnel and is therefore related to the structures that pass through it, namely fibres from flexor digitorum profundus and superficialis, the median nerve, flexor pollicis longus and flexor carpi radialis.
Also located in the vicinity are the muscles of the thumb and associated tendons.
Approximately 75% of the arterial supply is from branches of the radial artery through vascular perforations on the dorsal surface near the tubercle and waist 2. As vascular supply to the proximal pole is mainly retrograde, a fracture through the tubercle or the waist places the proximal pole at risk of avascular necrosis.
- bipartite scaphoid
- coalition with neighbouring bones (rare)
- scaphoid hypoplasia (as long as not associated with other skeletal dysplasias)
The scaphoid is the most radial of the proximal row of carpals, articulating with the distal radius, lunate and capitate. On the lateral view it is projected through the carpus.
The scaphoid has a single ossification centre, as do the trapezoid and trapezium. Ossification begins around the 4th year, and as with most ossification in the hand and wrist, it tends to occur earlier in females.
History and etymology
The term derives from the Greek word "skaphe" meaning boat.
The scaphoid may be visualised on a number of series of the distal upper limb including:
- 1.Sendher R, Ladd AL. The scaphoid. Orthop. Clin. North Am. 2013;44 (1): 107-20. doi:10.1016/j.ocl.2012.09.003 - Pubmed citation
- 2. Phillips TG, Reibach AM, Slomiany WP. Diagnosis and management of scaphoid fractures. Am Fam Physician. 2004;70 (5): 879-84. Am Fam Physician (link) - Pubmed citation
- 3. Slutsky D, Slade IJ. The Scaphoid. TNY. ISBN:B006367EKY. Read it at Google Books - Find it at Amazon
Anatomy: Upper limb
skeleton of the upper limb
- carpal bones (mnemonic)
- accessory ossicles of the upper limb
- accessory ossicles of the shoulder
- accessory ossicles of the elbow
- accessory ossicles of the wrist (mnemonic)
- joints of the upper limb
- sternoclavicular joint
- acromioclavicular joint
- glenohumeral joint
- scapulocostal joint (scapulothoracic joint)
- suprahumeral joint
- associated structures
- blood supply - scapular anastomosis
- ossification centres
- proximal radioulnar joint
- associated structures
- blood supply - elbow anastomosis
- wrist joint
- hand joints
- shoulder joint
- spaces of the upper limb
- pectoral region
- rotator cuff interval
- quadrangular space
- lateral triangular space
- medial triangular space
- cubital tunnel
- cubital fossa
- anatomical snuff box
- carpal tunnel
- Guyon's canal
- space of Poirier
- space of Parona
- extensor compartments of the wrist
- muscles of the upper limb
- shoulder girdle
- anterior compartment of the arm
- posterior compartment of the arm
- anterior compartment of the forearm
- posterior compartment of the forearm (extensors)
- thenar muscles
- hypothenar muscles
- intermediate muscles
- accessory muscles
- blood supply to the upper limb
- subclavian artery (mnemonic)
- axillary artery
- brachial artery (proximal portion)
- common interosseous artery
- posterior ulnar recurrent artery
- anterior ulnar recurrent artery
- proper dorsal digital artery
- deep palmar brach of the ulnar artery
- palmar carpal branches
- superficial palmar arch
- persistent median artery of the forearm
- radial artery
- innervation of the upper limb
- intercostobrachial nerve
brachial plexus (mnemonic)
- branches from the roots
- branches from the trunks
- branches from the cords
- terminal branches
- lymphatic drainage of the upper limb