Index finger extension and strength after extensor indicis proprius transfer.

We reviewed the long-term morbidity of the donor index finger following extensor indicis proprius tendon transfer in 34 patients with an average follow-up period of 8 years. An extension lag of the donor index was found to present in 24 patients. In all patients a reduced extension strength of the donor index finger was noticed, either measured dependently (with concurrent long finger extension) or independently (without long finger extension). Despite these findings, 30 of the patients described no limitations in their daily life activities. In nearly all patients the dependent extension strength was superior to the independent extension strength. To prevent an extension lag, the surgeon should avoid surgical trauma to the dorsal aponeurosis ("hood") by sectioning the index tendon proximal to the hood.