Sensory recovery after toe-to-finger transplantation: A three-year observation with quantitative sensory and functional sensibility tests

Nerve regeneration and functional recovery after toe-to-finger transplantation were studied by quantitative sensory and functional sensibility tests for a follow-up period of three years. There were 82 patients with a mean age of 32.4±9.7 years. A total of 135 toe transplantations were performed and the mean interval between injury and transplantation was 9.1±8.1 months. Quantitative sensory tests included pressure, pinprick, warm, cold, heat pain, cold pain, and pressure pain, whereas functional sensibility tests included light touch detection, 2-point discrimination, tactile localization, tactile discrimination, and movement detection. These tests were performed at 1,2,3,6,9,12,24 and 36 months after toe transplantation. Controls were the opposite corresponding normal fingers and normal toes. The onset of sensory return was related to the length of transplanted toes while the eventual recovery was related to the interval between injury and toe transplantation. The first appearance of sensations occurred at one month after toe transplantation in a small percentage of transplanted toes. The calculated mean rates of early nerve regeneration were 1.31 mm/day and 1.29 mm/day, respectively, for pressure and pinprick. The time course of the sensory function recovery showed three phases: an initial phase of about one month after toe transplantation when the sensations began to occur; an acceleratory phase of the following 4-6 months when there were a great increase in the number of responses and also an improvement in threshold and detection; and finally a plateau phase when the functional recovery became stable. The eventual sensibility of the transplanted toes was characterized by (1) Simple sensations were often better or equal to those of normal toes, but always less sensitive than those of normal fingers; (2) Discriminatory and localizing functions were satisfactory but apparently impaired; and (3) Sensations related to noxious stimuli exhibited a persistent hypersensitivity. The present date seem to indicate that toe-to-finger transplantation provides an alternative but good model to study nerve regeneration and functional recovery. This study also provides an opportunity to look into the functional transformation between structurally similar but functionally different body parts in man.