There are eight wrist bones, including the scaphoid bone, which is often fractured.
The scaphoid is a bone in the wrist. It is part of the first row of wrist bones, but it helps to link the two rows of wrist bones together.
Most of the scaphoid is covered with cartilage which contacts five other bones in the wrist and forearm.
The part of the scaphoid without cartilage is attached to ligaments and has blood vessels that come from the radial artery.
Bones need blood flow to heal. A broken or fractured scaphoid can have difficulty healing, or may never heal, because of a disruption of blood flow through the scaphoid.
An intact scaphoid is important and necessary for proper wrist function because of how it interacts with the other wrist bones.
The lunate is a bone in the middle of the wrist in the first row of wrist bones.
Like most of the wrist bones, it is almost entirely covered in cartilage.
This bone has a crescent shape when seen from the side and its large cartilage surface allows for significant wrist motion.
It is uncommon to break the lunate, but the lunate can be involved with dislocations of the wrist and can rub against the ulna if the ulna is too long compared to the radius bone.
The triquetrum is a bone on the small finger side of the wrist in the first row of wrist bones.
This bone adds stability to the wrist, gives the wrist a larger surface to bear weight transmitted from the hand, and makes a joint with other carpal bones including the pisiform.
This is a roughly trapezoidal-shaped bone in the second row of wrist bones and primarily holds the index finger metacarpal bone in place.
This bone is uncommonly injured.
The trapezium is a saddle-shaped bone in the second row of wrist bones, and it is the main place where the thumb metacarpal connects to the wrist.
This bone has an odd shape that allows the thumb to move in multiple directions, yet it stabilizes thumb as well.
There are two main problems seen with this wrist bone:
- Breaking (fracturing) the bone
- Arthritis developing between the trapezium and the bones it sits next to in the wrist and thumb.
The capitate is a large bone in the center of the second row of wrist bones. It forms joints with multiple bones in the wrist and hand.
It sits primarily under the middle finger metacarpal bone.
This bone makes an important contribution to wrist motion.
The hamate is a large, unusually shaped, bone that has an almost triangular shape when seen from the top and is located in the second row of wrist bones.
As with the other wrist bones, it serves as attachment points for multiple ligaments and works with multiple other bones.
It is one of the attachment points for the ligament involved in carpal tunnel syndrome.
It holds up the ring and little finger metacarpal bones.
The hamate can be injured in more than one way. Frequently, the hamate can break when people use the hand for punching.
Also, the hook of the hamate can fracture during a fall or if struck directly, such as when a baseball player swings a bat or golfer swings a golf club.
The pisiform is a small sesamoid bone (a bone within a tendon) that sits in the wrist and is in the flexor carpi ulnaris tendon.
Like other sesamoid bones, it changes the direction of pull of the tendon to which it is attached.
Occasionally, the pisiform can break or can have arthritis in the joint it makes with the triquetrum.
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