Patterns of recovery of sensibility in free flaps transferred to the foot: a prospective study

In a prospective study, the recovery of mechanical sensibility in five free flaps transferred to the foot was assessed qualitatively and measured with a quantitative method. The detection thresholds for 20, 80, and 240 Hz vibration frequencies were determined preoperatively from the recipient area and postoperatively from the flap at intervals of two to six months up to 14 to 21 months. Detection thresholds to mechanical vibration could be measured in the flaps immediately after operation before any sensory innervation could have taken place. The immediate postoperative thresholds were similar to the preoperative values obtained from an existing full-thickness defect; and where surgery had created a considerably deeper defect, they were elevated. The recovery of mechanical sensibility in the transferred flaps was found to be slow and incomplete. In three patients, after one year of follow-up, the flaps showed qualitative improvement in sensibility accompanied by a moderate lowering of detection thresholds obtained with 240 Hz vibration frequency. In two other flaps, there was no improvement in sensibility. In the reconstructions that had good soft-tissue stability, the flap was resistant to breakdown even before sensory recovery.