No abstract

Recovery of sensitivity to cold, warmth and pain caused by excessive heat in various types of free microvascular flaps was studied psychophysically in 27 patients who had undergone such operations four months to four years earlier. A thermal stimulator based on the Peltier principle and controlled by a microprocessor was used to measure the sensitivity to temperature in the transplants. The results were compared with the measured thresholds in the opposite sites in corresponding normal body areas. The present study showed that sensitivity to cold, warmth, and pain caused by excessive heat did return to some free microvascular flaps. According to the measurements the sensation started to return after 6 months in some flaps, and all types of thermal stimuli were felt by one patient as early as 10 months after operation. The return was more pronounced in younger people and in smaller flaps. If the hands, feet, or head defects were reconstructed with a thin skin flap (posterior aspect of thigh, dorsum of foot, or subscapular) the recovery of sensitivity was verified. Sensation returned to the musculocutaneous and osteomusculocutaneous transfers if they were on the hands or the head, or if they were sutured to healthy tissue with normal sensation. The main advantage of the psychophysical sensory testing method that we used is that it gave exact numerical data that made it possible to compare results among the different patient groups and even those obtained at different clinics and laboratories.

A clinical study of touch, pain, warm and cold stimuli and two-point discrimination was performed in 27 free flaps four months to four years after the microsurgical procedure. There were 5 free skin flaps (2 with nerve suture), 15 musculocutaneous, 4 muscle-covered with split skin grafts and 3 osteomusculocutaneous flaps transplanted to various sites on the body. The results show full or nearly full recovery of touch and pain sensation in all free skin flaps. The musculocutaneous and osteomusculocutaneous free flaps developed good sensation if firmly grown onto the healthy recipient skin with normal sensation. Muscle flaps covered with split skin grafts and all flaps surrounded by scar tissue had a clinical absence of sensation. This study and our earlier findings of the regeneration of nerves in free skin grafts, in skin flaps and in experimental free flaps, lead us to suggest that the healthy denervated skin of the free flap provides a strong neurotrophic stimulus to the cut cutaneous nerves in the edges of the recipient skin. Cutaneous nerves freely regenerate in the loose subcutaneous tissue of the flap. We therefore conclude that all free flaps with skin islands have a potential for developing sufficient protective touch and pain sensation and even some superficial sensitivity.

The regeneration of adrenergic nerves in free microvascular groin flaps in the rat was investigated. The adrenergic nerves were revealed with glyoxylic acid-induced fluorescence and with formaldehyde-induced fluorescence methods. In the control specimens taken from the contralateral groin, adrenergic nerves were seen in the erector pili muscles and as networks around arteries and arterioles. In the free flap four weeks postoperatively, a few regenerating adrenergic nerves were observed at the margins under the flap and following the pedicle. Eight weeks postoperatively many tiny regenerating nerves were observed to invade the flap at the margins and under it. Many regenerating nerves were observed to reinnervate the artery and vein, forming a nerve plexus in the pedicle. The number of single nerve fibres invading the flap at the margins decreased sixteen weeks postoperatively, but more nerves were observed along arterioles in the flap and pedicle. Twenty-four weeks postoperatively some regenerating adrenergic nerves were observed around arteries and arterioles in different areas in the flap and in erector pili muscles. A rich network of nerves remained around the pedicle. However, the reinnervation of the vasculature of the flap remained patchy and inadequate, and many arteries and arterioles remained without innervation.