Scaphoid bone
Encyclopedia
The scaphoid bone is one of the carpal
bone
s of the wrist
. It is situated between the hand and forearm on the thumb-side of the wrist (also called the lateral or radial side). The scaphoid bone is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward. It is approximately the size and shape of a medium sized cashew
.
of the hand, since there is also a bone in a similar position in the foot, called the navicular.
In reptiles, birds, and amphibians, this bone is instead commonly referred to as the radiale, because of its articulation with the radius
.
The inferior surface, directed downward, backward and laterally is also smooth, convex, and triangular, and is divided by a slight ridge into two parts, the lateral articulating with the greater multangular, the medial with the lesser multangular.
On the dorsal surface is a narrow, rough groove, which runs the entire length of the bone, and serves for the attachment of ligaments.
The volar surface is concave above, and elevated at its lower and lateral part into a rounded projection, the tubercle, which is directed forward and gives attachment to the transverse carpal ligament and sometimes origin to a few fibers of the Abductor pollicis brevis.
The lateral surface is rough and narrow, and gives attachment to the radial collateral ligament
of the wrist.
The medial surface presents two articular facets; of these, the superior or smaller is flattened of semilunar form, and articulates with the lunate bone
; the inferior or larger is concave, forming with the lunate a concavity for the head of the capitate bone.
The distal convex surface articulates with trapezium and trapezoid.
. It receives its blood supply primarily from lateral and distal branches of the radial artery
. Fortunately, it is relatively difficult to break, but is the most commonly fractured bone in the carpus, particularly because of its unique anatomy and position within the wrist. Approximately 60% of carpal fractures are scaphoid fracture
s.
The scaphoid primarily receives its blood from the distal end. Failure to heal of the fracture ( non union ) will lead to post traumatic osteoarthritis
of the carpus. Healing of the fracture with a non anatomic deformity ( frequently a volar flexed "humpback" ) can also lead to post traumatic arthritis . Non unions can result in loss of blood supply to the proximal pole which can result in avascular necrosis
of the proximal segment.
A condition called scapholunate instability can occur when the scapholunate ligament
(connecting the scaphoid to the lunate bone
) and other surrounding ligaments are disrupted.
Fractures of the scaphoid must be recognized and treated quickly, as prompt treatment by immobilization or surgical fixation increases the likelihood of healing in anatomic alignment avoiding mal union or non union. Delays may compromise healing. Even rapidly immobilized fractures may require surgical treatment, including use of a headless compression screw such as the Herbert screw
to bind the two halves together.
at the base of the anatomical snuff box
. It can also be palpated in the volar (palmar) hand/wrist. Its position is the intersections of the long axes of the four fingers while in a fist, or the base of the thenar eminence
. When felt in this position, the bone will feel to slide forward during radial deviation (wrist abduction), and flexion.
Clicking of the scaphoid, or no anterior translation can indicate scapholunate instability.
Carpus
In tetrapods, the carpus is the sole cluster of bones in the wrist between the radius and ulna and the metacarpus. The bones of the carpus do not belong to individual fingers , whereas those of the metacarpus do. The corresponding part of the foot is the tarsus...
bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s of the wrist
Wrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...
. It is situated between the hand and forearm on the thumb-side of the wrist (also called the lateral or radial side). The scaphoid bone is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward. It is approximately the size and shape of a medium sized cashew
Cashew
The cashew is a tree in the family Anacardiaceae. Its English name derives from the Portuguese name for the fruit of the cashew tree, caju, which in turn derives from the indigenous Tupi name, acajú. It is now widely grown in tropical climates for its cashew nuts and cashew apples.-Etymology:The...
.
Etymology
The etymology of the scaphoid bone is derived from the Greek skaphe which means "a boat," and the Greek eidos which means "form". This refers to the shape of the bone, supposedly reminiscent of a boat, and in older literature on human anatomy the scaphoid is referred to as the navicular boneNavicular bone
The navicular bone is a small bone found in the feet of both humans and horses.- Human anatomy :The navicular bone is one of the tarsal bones, found in the foot. Its name derives from the bone's resemblance to a small boat, caused by the strongly concave proximal articular surface...
of the hand, since there is also a bone in a similar position in the foot, called the navicular.
In reptiles, birds, and amphibians, this bone is instead commonly referred to as the radiale, because of its articulation with the radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
.
Surfaces
The superior surface is convex, smooth, of triangular shape, and articulates with the lower end of the radius.The inferior surface, directed downward, backward and laterally is also smooth, convex, and triangular, and is divided by a slight ridge into two parts, the lateral articulating with the greater multangular, the medial with the lesser multangular.
On the dorsal surface is a narrow, rough groove, which runs the entire length of the bone, and serves for the attachment of ligaments.
The volar surface is concave above, and elevated at its lower and lateral part into a rounded projection, the tubercle, which is directed forward and gives attachment to the transverse carpal ligament and sometimes origin to a few fibers of the Abductor pollicis brevis.
The lateral surface is rough and narrow, and gives attachment to the radial collateral ligament
Radial collateral ligament (wrist)
The radial collateral ligament extends from the tip of the styloid process of the radius and attaches to the radial side of the scaphoid , immediately adjacent to its proximal articular surface and some fibres extend to the lateral side of the trapezium The radial collateral ligament (external...
of the wrist.
The medial surface presents two articular facets; of these, the superior or smaller is flattened of semilunar form, and articulates with the lunate bone
Lunate bone
The lunate bone is a carpal bone in the human hand that may be distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row of the carpus region between the fore arm and hand...
; the inferior or larger is concave, forming with the lunate a concavity for the head of the capitate bone.
The distal convex surface articulates with trapezium and trapezoid.
Clinical significance
The scaphoid can be slow to heal because of the limited circulation to the boneBone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
. It receives its blood supply primarily from lateral and distal branches of the radial artery
Radial artery
In human anatomy, the radial artery is the main blood vessel, with oxygenated blood, of the lateral aspect of the forearm.-Course:The radial artery arises from the bifurcation of the brachial artery in the cubital fossa. It runs distally on the anterior part of the forearm...
. Fortunately, it is relatively difficult to break, but is the most commonly fractured bone in the carpus, particularly because of its unique anatomy and position within the wrist. Approximately 60% of carpal fractures are scaphoid fracture
Scaphoid fracture
A scaphoid fracture is the most common type of wrist fracture. Scaphoid fractures usually cause pain at the base of the thumb accompanied by swelling in the same area. Scaphoid fractures usually cause pain and sensitivity to palpation in the anatomic snuffbox at the base of the thumb accompanied...
s.
The scaphoid primarily receives its blood from the distal end. Failure to heal of the fracture ( non union ) will lead to post traumatic osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
of the carpus. Healing of the fracture with a non anatomic deformity ( frequently a volar flexed "humpback" ) can also lead to post traumatic arthritis . Non unions can result in loss of blood supply to the proximal pole which can result in avascular necrosis
Avascular necrosis
Avascular necrosis is a disease where there is cellular death of bone components due to interruption of the blood supply. Without blood, the bone tissue dies and the bone collapses...
of the proximal segment.
A condition called scapholunate instability can occur when the scapholunate ligament
Scapholunate ligament
The scapholunate ligament is a ligament of the wrist.The scapholunate ligament is an intraarticular ligament binding the scaphoid and lunate bones of the wrist together. It is divided into three areas, dorsal, proximal and palmar, with the dorsal segment being the strongest part. It is the main...
(connecting the scaphoid to the lunate bone
Lunate bone
The lunate bone is a carpal bone in the human hand that may be distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row of the carpus region between the fore arm and hand...
) and other surrounding ligaments are disrupted.
Fractures of the scaphoid must be recognized and treated quickly, as prompt treatment by immobilization or surgical fixation increases the likelihood of healing in anatomic alignment avoiding mal union or non union. Delays may compromise healing. Even rapidly immobilized fractures may require surgical treatment, including use of a headless compression screw such as the Herbert screw
Timothy Herbert
Timothy James Herbert is an orthopaedic surgeon specializing in hand surgery. He was born in Sheffield . He is known for his work with the scaphoid bone and related invention, the Herbert screw....
to bind the two halves together.
Palpation
The scaphoid can be palpatedPalpation
Palpation is used as part of a physical examination in which an object is felt to determine its size, shape, firmness, or location...
at the base of the anatomical snuff box
Anatomical snuff box
The anatomical snuffbox is a triangular deepening on the radial, dorsal aspect of the hand—at the level of the carpal bones, specifically, the scaphoid and trapezium bones forming the floor...
. It can also be palpated in the volar (palmar) hand/wrist. Its position is the intersections of the long axes of the four fingers while in a fist, or the base of the thenar eminence
Thenar eminence
The thenar eminence refers to the group of muscles on the palm of the human hand at the base of the thumb...
. When felt in this position, the bone will feel to slide forward during radial deviation (wrist abduction), and flexion.
Clicking of the scaphoid, or no anterior translation can indicate scapholunate instability.
See also
- Bone terminology
- Terms for anatomical location
- Preiser diseasePreiser diseasePreiser disease, or avascular necrosis of the scaphoid, is a rare condition where ischemia and necrosis of the scaphoid bone occurs without previous fracture. It is thought to be caused by repetitive microtrauma or side effects of drugs in conjunction with existing defective vascular supply to...
- Scaphoid fractureScaphoid fractureA scaphoid fracture is the most common type of wrist fracture. Scaphoid fractures usually cause pain at the base of the thumb accompanied by swelling in the same area. Scaphoid fractures usually cause pain and sensitivity to palpation in the anatomic snuffbox at the base of the thumb accompanied...
- Watson's testWatson's testWatson's test is a diagnostic test for instability between the scaphoid and lunate bones of the wrist.-Test procedure:To perform the test, the examiner grasps the wrist with their thumb over the patient's scaphoid tuberosity which is on the palmar side of the wrist...
External links
- SCAPHOID FRACTURES - FAQ - Navicular Fracture