POSTED: October 14, 2008

The Scaphoid - Most Frequently Injured and Hardest to Heal Carpal Bone

MotoGP world champion Casey Stoner is all too familiar with the delicacy of the scaphoid bone after reopening a break he experienced five years earlier. Stoner reported there had been no impact to cause the fracture to reopen; he was simply adjusting his back protector when he experienced a pain in the wrist. X-rays revealed that the bone he broke in 2003 had re-opened.

Casey Stoner's situation is not uncommon. Scaphoid fractures are recognized for their unpredictable and often complicated healing. Accounting for nearly sixty percent of all wrist fractures, the scaphoid is one of eight small bones that comprise the carpal bones in the wrist. The small cashew shaped bone located at the thumb side of the wrist is almost completely covered in articular cartilage and acts as a ball bearing within the wrist joint - allowing fluid movement between bones.

The scaphoid is a difficult bone to break. In fact, twice as much force is required to break the scaphoid than it takes to break one of the substantially larger forearm bones. This injury is most often the result of the strong force experienced in sports, such as basketball, football, riding a motorcycle. It is also seen in automobile and falling accidents, as an outstretched arm helps cushion the impact of a force or a fall consequently hyper extending the wrist joint.

Men are ten times more likely to fracture this bone than women. Scaphoid fractures generally occur in men between the ages of 20 and 40 years of age.

Adding to the complications of a scaphoid fracture is the difficulty in identifying a small break even when an injury is reported. Often times patients visit a physician only after a previous fracture of the scaphoid has healed improperly and is causing wrist pain - in some cases years later.

Since pain typically decreases quickly and bruising and swelling are rare, the fracture is often mistaken for a wrist sprain. Misdiagnosis combined with its very fragile blood supply makes a scaphoid fracture particularly precarious. The fracture often cuts off normal blood circulation to pieces of the bone.

The scaphoid has a unique and limited blood supply that can be easily disrupted by a fracture. The scaphoid's blood flow comes from a small vessel that enters the most distant part of the bone and flows back through the bone to give nutrition to the bone cells. Because there is only one, small blood supply, a fracture in the center of the bone can sever blood flow to the proximal portion of the bone. Since the blood supply cannot sufficiently reach the injury to facilitate adequate healing, the bone experiences avascular necrosis - which can result in bone and joint deterioration.

Scaphoid fractures are determined by a physical examination and x-rays. Magnetic resonance imaging (MRI) may also be performed to determine if there is other tissue damage. If the fracture is identified immediately, it will be treated with immobilization in a splint or cast. The severity of the fracture determines the length of time that a splint or cast is required. Even though immobilization is used, there is still a risk the fracture may not heal well and become classified as a non-union - a fracture that does not heal within several months. Scaphoid nonunions require special attention in order to avoid joint deterioration and osteoarthritis.

Scaphoid fractures are also classified as either complete or incomplete. Incomplete fractures do not extend across the entire bone. Complete scaphoid fractures extend across the entire bone and may require more casting and possibly an arthroscopic or open surgical procedure to stabilize the bone with a scaphoid bone screw, Kirshner wire or other fixation device.

Scaphoid fractures take a while to heal properly. Delay in treatment increases the risk of poor healing and the probability of more problems later in life. An untreated scaphoid fracture can lead to severe arthritis and may eventually require surgery to fuse or replace the joint.

Dr. Evan Collins is a leading orthopedic surgeon specializing in the hand and upper extremity, as well as a member of the leading orthopedic team of Houston Methodist Hospital - the official healthcare provider of the Houston Astro's and Texans. To learn more about scaphoid fractures or other injuries and conditions affecting the hand and upper extremity, log onto Or, call 713-441-3535 today.