Extensor Tendon Lacerations
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.
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.
The Extensor Tendons