Wrist bones – structure, functions, injuries and contusions. Fracture of the scaphoid bone of the wrist

Proven content

The function and structure of the wrist is one of the most complex in our body. The purpose of our wrists is to enable a wide range of motion. The wrist is made up of many joints, bones, ligaments, and tendons that work together to allow the wrist to move sideways, back and forth, up and down, rotate, and bend. Read the bones of the wrist and its most common injuries.

Wrist bones – structure and functions

The wrist bones are the bones that connect the distal parts of the radius and ulna bones of the forearm to the base of the five metacarpal bones of the hand. There are eight wrist bones, which are divided into two ranks:

1. proximal series,
2. distal series. 

The proximal row of wrist bones includes the bones:

1. boat-shaped,
2. lunar,
3. triangular,
4. pea-shaped.

In turn, the following series, counting in the same order:

1. quadrilateral greater,
2. quadrilateral smaller,
3. capitate,
4. hooked.

These bones make up most of the wrist skeleton and enable the various neurovascular structures and tendons that enter the wrist to reach certain muscle groups and bone structures, respectively, and provide the innervation and blood supply necessary for their function.

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Wrist bones – scaphoid fracture

A scaphoid fracture, while a relatively common wrist injury, is often ignored, overlooked, or mistakenly attributed to a wrist sprain. This is largely due to the subtleties of its symptoms. Unlike most other broken bones, the area around the scaphoid may not be noticeably swollen or intensely painful.

Due to the relatively harmless symptoms of a scaphoid fracture, they can be mistaken for a sprain and left undiagnosed for months or years, leading to long-term consequences of painful arthritis.

A scaphoid fracture is usually caused by a fall on an outstretched arm and is most common in young, active people. Often, an injury occurs during sporting events such as skiing or snowboarding, although it can also occur as a result of a car accident or a simple fall.

The reason why scaphoid fractures are difficult to heal is due to the anatomy of the blood supply to the bone. Most bones are covered with cartilage, the smooth shiny material that forms the joints and allows the bones to move. Blood vessels cannot pass through cartilage, they only pass through bone.

Since the scaphoid bone is mostly covered with cartilage, there is a limited area where arteries can enter the bone. In the scaphoid bone, the blood supply to the bone enters from the distal end, that is, the end towards the toes. This can be a problem in healing as most fractures occur in the middle or bottom of the bone. The blood supply to the proximal part, the part towards the elbow, may then be restricted.

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Scaphoid Fracture – Who Is At Risk?

Scaphoid fractures account for approximately 60 percent of all wrist fractures. They usually occur in men between the ages of 20 and 40, and are less common in children or the elderly. A rupture usually occurs when you fall on an outstretched hand. It is a common injury in sports and car accidents. The angle at which the hand hits the ground determines the injury. Here is the rule of thumb: if the wrist is bent at an angle of 90 degrees or more, the scaphoid bone will fracture, if the angle is less than 90 degrees, the forearm bone will break.

Fracture of the scaphoid bone – symptoms and signs

The main symptoms of a scaphoid fracture are:

1. pain and tenderness on the side of the thumb
2. movement (grasping) can be painful
3. there may be swelling on the back and thumb on the wrist side,
4. the pain may go away and then come back as a deep, dull pain
5. marked sensitivity to pressure on the “anatomical snuffbox” (the triangular area on the side of the hand between the two tendons leading to the thumb).

See: How to heal a pinched finger?

Scaphoid fracture – diagnosis

Diagnosis is based on a history of a wrist injury (usually a fall or accident), a clinical examination showing tenderness in the scaphoid area, and a painful Watson test (a maneuver to move the wrist back and forth with the examiner’s thumb on the scaphoid), and an x-ray examination showing the fracture . Sometimes a fracture is not visible on an x-ray. In some cases, even a CT scan is needed to diagnose the problem. Usually, with a background history and clinical examination, diagnosis will be made on the basis of a probable scaphoid fracture.

Scaphoid fracture – treatment

Treatment depends on the site of the fracture, the degree of displacement, and any associated injuries.

Plaster treatment: many scaphoid fractures are treated by immobilization in a cast that immobilizes the elbow, wrist, and thumb for six weeks, followed by just the wrist and thumb for an additional six weeks. However, healing time can range from six weeks for fractures in the upper part (towards the fingers) to six months or longer for fractures in the lower part (towards the wrist). The plaster should be checked regularly to make sure it fits snugly and prevents movement. After removing the plaster, rehabilitation helps to restore the range of motion and strength of the wrist,

Surgical treatment: some fractures are shifted by about 1 mm. They usually require surgical treatment. Scaphoid fractures accompanied by other injuries, usually a distal radius fracture, also require surgery. Moreover, with newer techniques, the risk of surgery is quite low. Some patients choose surgery because it usually means that they will not have to use plaster at all, but the splint.

Sometimes a bone graft is used to aid healing. There are two types of bone grafts. One is to use your own bone, often from the radius of your forearm. This could yield new bone cells to help fill the gap. Another type of bone graft is to take a bone fragment from a radial bone and transfer it to a scaphoid vessel attached to a microscopic blood vessel. There are certain times to do one or the other that we can discuss in the office.

Boat-shaped fractures often take a long time to heal. An untreated scaphoid fracture can lead to severe arthritis and eventually require surgery to fix or replace the joint.

Wrist bones – other injuries and contusions

Wrist injuries are common and there are many different types of injuries you can get, including wrist sprain, wrist fracture or ligament rupture. Most often, a wrist sprain is caused by a fall or sudden twist of the wrist. It is sometimes difficult to determine how serious a wrist injury is, as many of these injuries have similar symptoms. A twisted wrist means a ligament stretch or rupture. Ligaments connect many bones in the wrist.

Here are some signs of a wrist sprain:

1. edema,
2. pain when moving your wrist
3. bruises.

If your doctor confirms that you have sprained your wrist, you may have damaged one of the many ligaments in your wrist, but the two most commonly damaged ligaments in your wrist are the navicular ligament (inside the wrist) and the TFCC (outside the wrist), which is a triangular complex of fibrous cartilage. The TFCC is an extremely important structure in the wrist. It helps to connect the bones of the forearm with the little finger, ultimately stabilizing the entire side of the wrist.