DR HQ: Anatomy 101—Fractured wrists

When a player suffers a fractured wrist, the most common bone fractures are the hamate, pisiform or scaphoid bones. They make up part of the carpal bones in the wrist.

courtesy: www.sportsinjuryclinic.net


Hamate Bone
(All three bone write-ups from Wisegeek.com.)

The hamate bone is one of eight bones in the wrist known as the carpal bones. It is sometimes referred to as the unciform bone. Unciform means hook-shaped, and the hamate has a hook-like section protruding from the main, triangle-shaped bone which is known as the body. The hook sticks up into the palm, where it is sometimes injured, either as the result of a fall or during sports such as golf or tennis, where a club or racquet is gripped and swung in a way that can place stress on the bone and cause a fracture. Hamate fractures may be treated using a cast, but surgery may be needed in more complex cases.

courtesy: www.sportsinjuryclinic.net

Types of Fractures
Two different types of fractures may affect the hamate bone. In the first type, the hook breaks away from the body of the bone, perhaps following repeated use of a bat or racquet, or as the result of a direct blow during a fall or a single, forceful swing of a golf club. With the second type of hamate fracture, the body of the hamate is broken, and this can follow a direct blow or crushing injury involving the wrist. Symptoms of a broken hamate bone include pain, a weak grip, and if the ulnar nerve, which runs nearby, is also damaged, the fourth and fifth fingers may tingle and feel numb. Sometimes, ligaments and muscle tendons rub against the fractured bone causing possible fraying, and even tearing, if the injury is not treated.

Hamate bone fractures can be difficult to diagnose on an X-ray, as the wrist bone may be hidden by its neighbors. A CT, or computerized tomography, scan is sometimes used to obtain a better image of the injured hamate. When a fracture involving the hook of the hamate is treated early, simply immobilizing the arm in a cast may be enough to allow the bone to heal. Sometimes, especially if a person does not seek treatment straight away, there is a risk that part of the hamate bone could die off and the hook might have to be removed. While hook removal is the more commonly performed operation, an alternative procedure exists which involves opening up the wrist and fixing the hamate bone together with screws. Downtime can be anywhere from 4-8 weeks depending on the severity of the injury.


Pisiform Bone

The pisiform is a bone in the human hand located in the wrist. It is also referred to as the lentiform bone. It is located below the pinky finger on each hand.

Courtesy: www.accessmedicine.ca

More specifically, it is located where the ulna, which is the forearm's inner bone that meets up with the carpus cluster. The bone is about the size and shape of a pea — pisiform is Latin for "pea-shaped." Although the bone is very small, it is still a little bit larger than the smallest bone in the body, the stirrup bone located in the ear.

The pisiform is a sesamoid bone, which means it is located within a tendon. In humans most sesamoid bones are found in the hand, foot or knee and they help to increase flexibility and movement. This bone is unique to other wrist bones in that it does not work with other bones in the joints of the wrist. Its sole function seems to be to increase torque and rotation in the wrist and the hand.

Types of Injuries
Pisiform fractures are usually linear fractures and happen most often when the bone is struck directly. Other hand injuries and fractures are usually present when the pisiform is broken. This can lead to injuries of the pisiform bone being overlooked or misdiagnosed, as they are so rare that they are sometimes missed completely by doctors who are focused on more common bone breaks.

Effects of the bone break can be nerve or ligament damage in the surrounding area. Injuries in the hand may also lead to the bone being dislocated, although this is also uncommon. When the bone is injured or broken, wrist and grip strength can be affected.

Often with a break of this bone, treatment includes completely excising it. Leaving the broken bone in the hand usually leads to chronic hand and wrist pain. After the bone is excised the pain usually goes away, and side effects to the removal are marginal. While the wrist, hand and grip strength are adversely effected by its removal, the difference between the wrist with the bone or without it is usually nominal. A player can miss between 4-6 weeks with this injury depending on the type and what else was damaged.


Scaphoid Bone

The scaphoid bone, also called the navicular bone, is the largest bone in the proximal row of the wrist, the highly flexible region between the forearm and the hand. The flexibility of the wrist can be largely attributed to its unique and complex composition, marked by two horizontal rows of small bones called carpals. The scaphoid bone belongs to the proximal row of carpals, or the row closest to the trunk of the body and farthest from the fingertips. The term proximal is a comparative anatomical term that refers to the point closest to the midline of the body, as opposed to distal, which refers to the point farthest from the midline. When comparing the elbow and the fingertips, for example, the elbow is proximal and the fingertips are distal.

Courtesy: ericksonhandsurgery.com

Types of Injuries
The scaphoid bone is the most commonly broken bone in the wrist and is difficult to heal because of limited circulation, or blood flow. These breaks are usually the result of a patient trying to break a fall with an outstretched palm. If a break is suspected, patients should seek prompt medical attention, as improper healing can lead to complications such as avascular necrosis, in which the bone dies from lack of blood supply. Symptoms of a scaphoid bone fracture may include pain and swelling in the wrist, particularly near the base of the thumb. A physician will feel the wrist to determine the source of the pain and then take an X-ray, an exam used to take an image of bones, to diagnose the break.

If the physician diagnoses a fracture, he will likely recommend several weeks in a cast and schedule follow-up visits with the patient to check the progress of the healing through X-ray. If the fracture does not heal, it is considered a non-union and may require an electrical stimulator. The electrical stimulator is worn like a wristband and transmits electrical currents into the wrist to aid the healing process. If the injury is old or other treatments aren’t working, the physician may recommend surgery on the scaphoid bone. This usually involves fusing the bone together with a bone graft, which inserts bone tissue from another part of the body into the fracture, and a metal pin to secure the bone.

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  For more information about the terms used in this article, see our Glossary Primer.