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The scaphoid bone, also known as the os scaphoideum, is the largest of the proximal row of carpal bones. It is located on the radial side of the wrist and is crucial for stability and movement at the wrist. The scaphoid is involved in the movement of the wrist, along with the lunate and distal surfaces of the radius and ulna. It forms the radial border of the carpal tunnel and serves as an attachment site for various ligaments and muscles. While there are no direct musculotendinous attachments to the scaphoid, it is influenced by extrinsic musculotendinous structures. The scaphoid receives its blood supply primarily from the radial artery, which accounts for around 70-80% of its vascularity.
| Characteristics | Values |
|---|---|
| Musculotendinous attachments | None |
| Ligamentous connections | Proximally, toward the distal radius; distally, toward the distal carpal row; ulnarly, toward the adjacent lunate |
| Radial artery | Crosses the dorsal surface of the scaphoid; provides 70-80% of blood supply |
| Vascular supply | Predominantly retrograde |
| Flexor tendons | Fibers from flexor digitorum profundus and superficialis, flexor pollicis longus, and flexor carpi radialis |
| Extensor tendons | Extensor carpi radialis brevis and longus |
| Position | Between the proximal and distal rows of carpal bones; radial side of the wrist; lateral most of the carpal bones in the proximal row |
| Shape | Boat-like; triangular proximal surface; narrow lateral surface; concave palmar surface with a distal tubercle; narrow dorsal surface |
| Function | Stability and movement at the wrist; forms the radial portion of the carpal tunnel |
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What You'll Learn
The scaphoid has no direct muscle attachments
The scaphoid bone, also known as the os scaphoideum, is the largest of the proximal row of carpal bones. It forms the radial portion of the carpal tunnel and is crucial for stability and movement at the wrist. The scaphoid serves as a link between the two rows of carpal bones and is involved in the movement of the wrist, along with the lunate bone, by articulating with the radius and ulna.
Despite its important role in the wrist's mechanical integrity, the scaphoid has no direct muscle attachments. However, it does have ligamentous connections and articulates with several other bones. The scaphoid has three separately directed ligamentous connections: proximally toward the distal radius, distally toward the distal carpal row, and ulnarly toward the adjacent lunate. The palmar radiocarpal ligament consists of three distinct fibre complexes, two of which insert on the scaphoid. The radial collateral ligament is attached to its lateral surface.
The scaphoid also articulates with the radius, lunate, trapezoid, trapezium, and capitate. The palmar surface of the scaphoid is concave and forms a distal tubercle, providing an attachment site for the transverse carpal ligament. The proximal surface is triangular, smooth, and convex, while the lateral surface is narrow and attaches to the radial collateral ligament. The medial surface has two facets: a flattened semi-lunar facet articulating with the lunate bone and an inferior concave facet articulating with the head of the capitate bone.
The scaphoid is located on the radial side of the wrist, adjacent to the styloid process of the radius. It is positioned at the intersections of the long axes of the four fingers when in a fist or at the base of the thenar eminence. The bone can be palpated at the base of the anatomical snuff box or in the volar (palmar) hand/wrist. The word "scaphoid" is derived from the Greek word "skaphe" meaning boat, referring to the boat-like shape of the bone.
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The bone is involved in wrist movement
The scaphoid bone, also known as the os scaphoideum, is the largest of the proximal row of carpal bones. It is important for stability and movement at the wrist. The scaphoid is situated between the proximal and distal rows of carpal bones. It is located on the radial side of the wrist, adjacent to the styloid process of the radius. It articulates with the radius, lunate, trapezoid, trapezium, and capitate. Over 80% of the bone is covered in articular cartilage. The word "scaphoid" comes from the Greek word "skaphe," meaning boat, and refers to the bone's boat-like shape.
The scaphoid is one of the eight carpal bones of the hand. It is classified as a short bone and is the lateral-most of the carpal bones in the proximal row. Together with the lunate and triquetrum, its proximal surface articulates with the distal end of the radius to form the radiocarpal (wrist) joint. This joint is crucial for wrist movement and stability. The scaphoid serves as a link between the two rows of carpal bones, and with wrist movement, it can flex from its position in the same plane as the forearm to perpendicular.
The scaphoid has a prominent tubercle on its lateral palmar surface, which serves as an attachment point for the abductor pollicis brevis and the flexor retinaculum. The radial collateral ligament is also attached to its lateral surface. The palmar radiocarpal ligament consists of three distinct fiber complexes, two of which insert on the scaphoid. The dorsal radiocarpal ligament passes the proximal pole of the scaphoid without direct attachment. The scaphoid is also acted on by flexor and extensor tendons, such as the Flexor Carpi Radialis Tendon and the Extensor Carpi Radialis Brevis and Longus.
The scaphoid is involved in wrist movement along with the lunate bone, as they articulate with the radius and ulna to form the major bones involved in this action. The scaphoid is the most radial of the proximal row of carpals, articulating with the distal radius, lunate, and capitate. It forms the radial border of the carpal tunnel and is related to the structures that pass through it, including the median nerve and flexor muscles. The scaphoid is crucial in the wrist's mechanical integrity, and fractures of the scaphoid are common due to its connections with the two rows of carpal bones.
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It forms the radial border of the carpal tunnel
The scaphoid bone is the largest of the proximal row of carpal bones, providing structural support to the hand and wrist. It is situated on the radial side of the wrist, below the radius, and is involved in wrist movement. The scaphoid is also referred to as the os scaphoideum, derived from the Ancient Greek word "skaphe" meaning boat, due to its boat-like shape.
The scaphoid forms the radial border of the carpal tunnel, which is crucial for the stability and movement of the wrist. The carpal tunnel is a passageway in the wrist that houses and protects several important structures, including tendons and nerves. The radial border, formed by the scaphoid, is the thumb-side boundary of this tunnel. This positioning of the scaphoid bone is integral to the overall function of the wrist.
The scaphoid bone serves as a link between the two rows of carpal bones, allowing for a wide range of wrist movements. It articulates with several surrounding bones, including the radius, lunate, trapezoid, trapezium, and capitate. This articulation with the radius and ulna, in particular, is crucial for wrist movement. The scaphoid can flex from its position in the same plane as the forearm to a perpendicular position during wrist movement.
The radial border of the carpal tunnel, formed by the scaphoid, is also important for the passage of various structures. These include fibres from the flexor digitorum profundus and superficialis, the median nerve, flexor pollicis longus, and flexor carpi radialis. Additionally, the muscles and tendons associated with the thumb are located in close proximity to the radial border.
The scaphoid bone is susceptible to fractures, which are the most common type of carpal bone injuries. This is due to its connections with the two rows of carpal bones. Fractures of the scaphoid can occur following a fall onto a hyperextended hand. Given the limited circulation to the bone, healing can be slow, and prompt treatment is crucial to ensure proper alignment during the healing process.
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The scaphoid is the largest bone in the proximal carpal row
The scaphoid has a prominent tubercle on its lateral palmar surface, which serves as an attachment point for the abductor pollicis brevis and the flexor retinaculum. It also provides an attachment site for the radial collateral ligament. The bone has three ligamentous connections: proximally toward the distal radius, distally toward the distal carpal row, and ulnarly toward the adjacent lunate. The scaphoid is also acted on by flexor and extensor tendons, such as the flexor carpi radialis tendon and the extensor carpi radialis brevis and longus.
The scaphoid is crucial in maintaining the wrist's mechanical integrity. It is the most radial of the proximal row of carpals, articulating with the distal radius, lunate, and capitate. It also articulates with the trapezoid, trapezium, and the head of the capitate bone. The scaphoid serves as a link between the two rows of carpal bones and can flex from its position in the same plane as the forearm to perpendicular with wrist movement.
The scaphoid is susceptible to fractures, which are the most common injury among the carpal bones due to its connections with the two rows of carpal bones. These fractures must be recognized and treated quickly to increase the likelihood of the bone healing in anatomic alignment. The bone's vascular supply is predominantly retrograde, receiving its blood supply primarily from the radial artery (70-80%).
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It is susceptible to fractures and avascular necrosis
The scaphoid bone is the most commonly fractured carpal bone. It is located on the radial side of the wrist, below the radius, and is involved in wrist movement. The scaphoid is susceptible to fractures due to its position and connections with the two rows of carpal bones. Fractures typically occur as a result of a fall on an outstretched hand, with the wrist hyperextended, or with direct axial compression.
The scaphoid receives its blood supply from branches of the radial artery, with the dorsal branch supplying 70-80% of blood, travelling in a retrograde fashion from distal to proximal. This tenuous blood supply means that fractures can easily compromise it, leading to avascular necrosis (AVN) and degenerative wrist disease. The more proximal the fracture, the higher the risk of AVN.
Avascular necrosis is a common complication of scaphoid fractures, occurring in around 30% of cases. It arises when the fracture disrupts the blood supply, leading to the death of bone tissue due to oxygen deprivation. The risk of AVN is particularly high in fractures of the proximal third of the scaphoid, with the middle third being the most frequent fracture site and having a moderate risk of AVN. Fractures in the distal third rarely result in AVN.
Non-union is another complication of scaphoid fractures, where the bone fails to heal properly due to inadequate blood supply. This can lead to wrist osteoarthritis, causing symptoms such as aching, decreased range of motion, and pain during activities. Treatment for non-union may involve anti-inflammatory medications, wearing a splint, steroid injections, or surgery.
Prompt recognition and treatment of scaphoid fractures are crucial to improving the likelihood of the bone healing in proper alignment and reducing the risk of complications such as avascular necrosis and non-union. Treatment options include immobilisation with a cast or splint, surgical fixation, and screw fixation for unstable fractures.
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Frequently asked questions
The scaphoid is one of the eight carpal bones of the hand. It is the largest carpal bone in the proximal carpal row and is crucial to the wrist's mechanical integrity.
There are no musculotendinous attachments to the scaphoid bone. However, the abductor pollicis brevis and the flexor retinaculum attach to the scaphoid tubercle.
The scaphoid has three ligamentous connections: proximally toward the distal radius, distally toward the distal carpal row, and ulnarly toward the adjacent lunate. The palmar radiocarpal ligament also attaches to the scaphoid.
The scaphoid functions as a link between the proximal and distal carpal rows through ligamentous attachments and articular mechanics. It is important for stability and movement at the wrist.
The scaphoid receives 70-80% of its blood supply from the radial artery. The remaining 20-30% comes from the dorsal carpal branch and the superficial palmar/volar branch.
