The extensor tendons are the structures on the back of your hand that extend the fingers (Figure 10). The tendons are like ropes that connect the muscles to the finger bones. The extensor tendons are often cut when the back of the hand or the back of the finger is lacerated. The seriousness of extensor tendon injuries have classically been underestimated. However, over the past decade or so it has become clear that extensor tendon injuries are complicated problems with at least as many problems as flexor tendon injuries. The extensor tendon system of the hand is actually even more complicated than the flexor tendon system. If extensor tendon repairs are not done well there are at least as many complications as following flexor tendon repairs, if not more. Extensor tendon lacerations should optimally be fixed within a couple of weeks although delays are not quite as problematic as for flexor tendon injuries. The repair itself is not an emergency, and is best done after a few days, once the wound is healing without any evidence of infection.
If over 50% of an extensor tendon is cut, it needs to be repaired. Extensor tendon lacerations of less than 50% do better if not repaired. This is because repairs of smaller extensor tendon lacerations create scar that hinders gliding and lead to stiffness for no significant gain in tendon strength. 50% of the extensor tendon is strong enough, and all that is needed.
The main problem with any extensor tendon injury is stiffness. This is especially common when the extensor tendon is lacerated in the finger. In the finger, the extensor tendon is very flat and thin. Because the extensor tendon is thin, it’s not very strong and, after surgery, the finger must often be immobilized, usually by pinning it, to protect the delicate repair. Repairs around the distal interphalangeal (DIP) joint (the smallest joint nearest the finger tip) are often pinned for 6 weeks. Repairs about the proximal interphalangeal (PIP) joint (the middle joint of the finger) are often pinned for about 3 weeks, following which a special hinged splint with a spring or rubber band in it are worn for another 3 weeks.
Because the extensor tendon is flat in the finger, it has a very large surface area that quickly scars to the underlying bone. Because it is important to balance motion with protection of the repair, it is crucial to have a good certified hand therapist (i.e. not just any therapist) supervise the post-operative rehabilitation of extensor tendon injuries and repairs. Even so, it is not uncommon to require a second surgery to release scar tissue to regain finger motion.
The extensor tendon is usually big enough over the hand itself so that when it’s repaired, early controlled motion can be started and no pinning is required. A dynamic splint (splint with rubber bands to help extend the fingers and take the stress off of the extensor tendon) is worn for 4-6 weeks to protect the repair.
Extensor Tendon Repair
The extensor tendon system is very complex, with tight tolerances. If the tendon is shortened even 2-3 mm, then the ability to close the finger and make a fist can be lost. If the tendon is lengthened even 2-3 mm, then full finger extension will not be achieved. That’s why these injuries should probably always be repaired in the operating room, not the emergency room, by a fellowship-trained hand surgeon, not a generalist.
While extensor tendon lacerations are very serious injuries, if the time and effort is put into therapy supervised by a skilled certified hand therapist and restrictions are observed, good results are common. After surgery, the wound should be kept clean and dry for 3 days. Bathing is safer than showering, because the hand can be kept out of the bath tub. Wrap a towel around the hand and then place it inside a plastic bag secured with rubber bands. If a bathtub is not available, the best cast protector is made by Walgreens. After 3 days the wound can get wet in the shower, blotted dry, and band-aids or a light dressing that will not limit motion can be applied. Please do not get the wound dirty, or submerge it under water, until the stitches come out, 2-3 weeks after surgery.