FLEXOR TENDON LACERATION
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What is a Flexor Tendon Laceration?
A laceration to the palm or finger can cut one of our finger tendons. Our tendons attach our muscles to bones so that we can move our fingers. In a flexor tendon laceration, we lose the ability to bend the finger. A flexor tendon allows you to grip with your fingers (while an extensor tendon allows you to straighten out your finger).
Our finger tendons run a long distance. The muscles that control our fingers actually start in our forearm, and then they turn into tendons (thick bands) at the wrist, and these tendons then travel to the tips of our fingers and attach to the bone.
Cutting the tendon at different locations along its path will affect how its treated. There are 5 zones where the tendon can be cut. Zone 5 is from the muscle to the wrist. Zone 4 is within the carpal tunnel. Zone 3 is within the hand. Zone 2 is from the beginning of the finger to the middle of the finger, and Zone 1 is to the tip of the finger (a Zone 1 injury is also known as a Jersey finger, see talk). In zone 1 and 2 the tendon is covered by a flexor sheath, and lined by the epitenon which allows for gliding and must be maintained for good motion.
How is a Flexor Tendon Laceration diagnosed?
Injury to a flexor tendon will prevent you from bending the affected finger. A person will come to the emergency room or office with a cut on the palm of their finger, hand or wrist and will say that they cannot fully bend their finger.
Sometimes the cut tendon can be seen directly. Sometimes the diagnosis is made by examining the fingers and evaluating their function. Doctor look for tenodesis effect: by extending the wrist the flexor tendons are pulled tight and this bends the fingers. If a finger does not bend with this maneuver, there is a high chance the tendon is torn.
Its also important to see if the artery or nerve of the finger has also been cut. The arteries and nerves travel along the sides of each finger and are often injured from a laceration that cuts the tendon.
How is a Flexor Tendon Laceration treated?
Treatment depends on the severity of the tendon injury. If the laceration involves less than 50% of the tendon, then we immobilize the hand for a few days to give time for healing and then start early passive motion. The splint is kept for 6 weeks, then another 6 weeks of wearing the splint sometimes.
If the tendon is torn more than 50% it needs to be repaired.
Repair is typically not an emergency and can be done within a few weeks of the injury, but sooner the better (to minimize finger stiffness and tendon contracture).
As long as the tendon is repaired within a few weeks of injury, the surgery involves tying the two ends back together. The tendons are tied using suture. The center of the tendon is tied together typically with 4 stitches (core sutures), and the outside of the tendon is also tied (epitendonous repair).
What is the long term outcome?
There is a significant concern for complications with this surgery, particularly the development of stiffness after surgery. This is becomes as the tendon heals, theres a good chance scar tissue forms between the tendon and the sheath which prevents smooth gliding of the tendon. Motion of the tendon prevents scar from forming, however, by moving the tendon you are placing stress across the stitches that repaired the tendon, and you risk re-tearing. Therefore, a compromise as been achieved, where the fingers are moved by someone else (without flexing your muscles) which reduces the strain across the healing tendon but allows for motion.