Sprained Thumb
Scenario:
Rounding a corner on the South Mountain race loop, your tires begin to dig into the soft
shoulder. For a second, you think you're going to pull it out. But then the bike flips
sideways, and you're flying off the trail. As you catch yourself, your thumb hangs up in
the soft dirt and bends down towards your wrist.
Description:
A sprain is a stretching of ligaments -- the tissues that hold two bones together. In the
thumb, you have these ligaments on the inner and outer sides of each joint, and on the
underside of each joint. When an accident bends the joint in a direction it's not supposed
to go (most commonly, bending backwards), it injures the ligament. Ligament injuries come
in three degrees of seriousness: 1st degree = stretching, 2nd degree = partial tear, and
3rd degree = complete rupture.
If the spraining force bends the thumb straight back (in the direction of the thumbnail), the sprain usually won't be serious. But it forces the thumb laterally downward (force on the side of the thumb that faces the index finger, pulling it down towards the wrist), it can rupture the ulnar collateral ligament, making the thumb unstable.
Concerns:
A rupture of the ulnar collateral ligament (located on the side of the thumb right where
it meets the skin fold coming over from the index finger) is serious. Of course, the same
forces that sprain a thumb can also cause dislocation, tendon rupture, fracture, or volar
plate injury. So you should assess careful for the signs of serious injury. Only if the
injury seems trivial should you self-diagnose a sprain.
See the doctor for an injured finger if:
there's significant swelling or deformity
there's pain when the thumb is resting (after the first hour)
you can't move the joint fully
there's severe pain with motion of the thumb
there's numbness or weakness
there's weakness at the base of the thumb with pinching motion
the thumb can be bent outward at either knuckle
Immediate care:
Rest, Ice, Compress, and Elevate. Immediately elevate the injured part and apply an ice
bag. If the distant knuckle is injured, splint it. If the pain is at the first knuckle,
you'll probably need to see the doctor for adequate splinting. (And maybe an x-ray.)
Your doctor may do a stress test for ruptured ulnar collateral ligament: pulling downward on the side of the thumb while bracing the MCPJ with the thumbtip. Compare to the normal side. The thumb can bent outward if the ligament is ruptured.
Ongoing care:
For the first 48 hours, repeat ice and elevation 1/4 of the time (for example, 30 minutes
of ice every two hours). Continue splinting for a few days. As the pain subsides, return
to activities. Often you can protect the injured finger by "buddy taping,"
taping it to an adjacent bigger stronger finger. It will take about three weeks for the
sprain to heal. As you resume sports, remember the rule: "If it hurts, don't do
it." If the finger becomes increasingly swollen, or remains weak or painful in
routine use, go to the doctor.
Finger rehab:
After the first few days of splinting, start range of motion exercises.
Range of motion: Warm the finger for 10 minutes (heating pad or sink of warm water).
Gently bend the finger until it begins to feel uncomfortable, then hold the stretch for 30
seconds. Rest for a minute, then do it again. Repeat 10 times. Now straighten the finger
and hold for 30 seconds, rest a minute, and repeat 10 times. If the finger has increased
discomfort after the exercises, ice the wrist for 20 minutes after the exercises. Do the
exercises twice a day.
Watch for:
If the injured area doesn't improve promptly, see the doctor.
