I’m lecturing Friday on hand lacerations: injuries to the flexor tendons, extensor tendons, nerve and arteries of the fingers and hand. One of the biggest changes in the treatment of hand lacerations is related to the extensor tendons. When I was training in the 1990’s, extensor tendon lacerations were not very respected. The most junior resident would simply repair them under local anesthesia in the emergency room. However, hand surgeons have learned that the extensor tendon system of the hand is even more complex than the flexor tendon system and that, if not done well, extensor tendon repairs have as many, if not more, complications than flexor tendon repairs.
The extensor tendons are the structures on the back of your hand that extend your fingers. They are often cut when the back of the hand is lacerated. If over 50% of a extensor tendon is cut, it needs to be repaired. Extensor tendon lacerations of less than 50% do better if not repaired. Repairs of smaller extensor tendon lacerations hinder gliding and lead to stiffness for no significant gain in tendon strength. 50% of the extensor tendon is strong enough, and all you need.
Because the extensor tendons are small in the finger, if they’re cut here the finger often needs to be pinned to protect the repair. Repairs around the distal interphalangeal (DIP) joint (the smallest joint nearest the finger tip) are pinned for about 6 weeks. Repairs about the proximal interphalangeal (PIP) joint (the middle joint of the finger) are 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.
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 usually used. 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 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. However, the repair itself is not an emergency, and is best done once the wound is healing without any evidence of infection. The optimal time for repair is probably within 14 days following laceration.
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 be immobilized to protect the delicate repair. Because the extensor tendon is flat, 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 (ie. not just any therapist) supervise the 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.
While they are often problematic, extensor tendon lacerations will have the best chance for a good result in a motivated patient who is treated by an experienced hand surgeon, with the rehabilitation supervised by a skilled certified hand therapist.