When the thumb is sprained, people have difficulty grasping objects between their thumb and index finger, and the thumb is painful and swollen.
Doctors diagnose a thumb sprain by examining the thumb, sometimes after giving the person an anesthetic to make the examination less painful.
Most thumb sprains are immobilized with a thumb spica splint, but sometimes surgery is needed.
Most thumb sprains involve the main ligament at the base of the thumb on the inside of the hand. This ligament is often sprained when people fall on their hand while holding a ski pole. Thus, this injury is often called skier's thumb. This ligament may also be injured by jamming the thumb backward on a hard surface when falling or on a ball as when catching a baseball. Repeated overstretching of the joint can also tear the ligament, as occurred in English gamekeepers, who broke the necks of rabbits with their hands. Thus, this injury is sometimes called gamekeeper's thumb.
Sometimes when the ligament tears, it pulls a small piece of bone from the bottom of thumb bone (called an avulsion fracture).
To determine whether the ligament is torn and, if so, how badly, doctors ask the person to move the injured thumb in various ways. Doctors then move the thumb in various directions while holding the rest of the hand still (called stress testing). If the thumb joint is loose, a sprain is likely. Sometimes before doctors examine the thumb, a local anesthetic is injected near the injured thumb to make the examination less painful. Doctors may also examine the uninjured thumb and compare it with the injured thumb.
X-rays are taken from several angles to check for fractures. X-rays may be taken while the doctors applies pressure to the injured thumb (called a stress x-ray).
For most sprains, the thumb is immobilized with a thumb spica splint. The splint is worn for several weeks until the ligament heals. After a few weeks, people may take the splint off to do strengthening exercises, then put the splint back on. People should continue this regimen for 2 to 3 weeks.
If the ligament is badly torn or if a piece of broken bone needs to be put back in place, surgery is needed. Surgery is also needed if the ligament does not heal after being splinted for several weeks. After surgery, people need to wear a thumb spica cast for 6 to 8 weeks. A thumb spica cast is rigid. Like the thumb spica splint, the thumb spica cast prevents the thumb from moving. It covers the wrist and forearm and keeps the thumb in a neutral position (as shown in thumb spica split, above).