Extensor substitutions are performed as a surgical treatment for clawing of the toes 2, 3, 4, and 5 (the lesser toes). When excessive pull of the tendons that pulls the toes upwards (long extensor tendons) occurs, these toes will tend to flex up which predisposes them to the claw toe deformity. The extensor substitution is designed to alleviate and decrease the pull from the extensor tendons.
The procedure itself involves making an incision over the top of the forefoot, often at the oblique. The extensor tendons are identified and are then cut. These tendons are then often sutured into the mid foot or the tendon on the side of the foot, so that the pull from the muscles will still serve to flex up the ankle joint but not the toes. The far ends of the tendons are then attached to the smaller extensor tendons that originate in the foot extensor digitorum longus (EDB) tendons. This is performed so that the tendons are in a more lengthened position. This has two effects; First, there is lengthening of the extensor tendons so that the clawed toes tend to fall back into a more neutral position; Second, the smaller muscle belly in the foot is not as strong, and therefore there is not going to be as much dynamic force on the toes. This makes it less likely for the deformity to recur.
Indications for this procedure are clawtoe deformities of the lesser toes. This is procedure is often performed when the clawtoe deformities are flexible (the toes can still be straightened) and a less powerful correction is indicated.
Recovery from this procedure requires a six-week period of relative immobilization of the toes. This is often done by pinning the toes in a straight position. This allows the tendon repairs to heal. During this time, patients may be allowed to weight bear through the heel, but they are often encouraged to significantly limit their weight bearing activities.
Complications that are specific to the extensor substitution procedure include:
- Failure of the tendon transfers to knit together. This may result in limited or absent extension of the involved toe.
- Incomplete or over correction of the toe deformity. It can sometimes be quite difficult to get the lesser toes perfectly aligned and to ensure that the tension from the new muscle unit that has been transferred into the tendon is working appropriately. Therefore, the toes may not line up in a perfectly even manner.
- Nerve injury. There can be injury to the sensory nerves that supply the top of the foot with resulting numbness or burning sensation over the top of the foot, extending into the toes.
Edited June 6, 2017