A novel experimental model for studying efficacy of cryosurgery in keloids.

BACKGROUND: Intralesional cryosurgery is effective in the treatment of keloids; however, clinical studies have presented diversified results. OBJECTIVE: A novel, reproducible model for biophysical studies on intralesional cryosurgery of keloids is presented. METHODS: Triplicate studies with a cryosurgical needle on 37°C-heated potatoes, which exhibit identical specific heat and similar heat conductivity with human skin, were performed. RESULTS: No complete potato freezing resulted through a cryosurgical needle. The limited tissue damage achieved had a double concave form. The needle induced lower temperature and stronger tissue damage at the distal exit than the proximal entrance site. The concave form of tissue damage flattened with time at the area under the needle. Needle freezing with puncture distances of 0.5, 1.0 and 1.5 cm from the potato surface only revealed freezing temperatures within the 0.5 cm range. At any needle depth, tissue damage was detected at only an area to about 1 cm under the needle. CONCLUSION: Clinical extrapolation of these experimental findings indicates a proper needle positioning towards the keloid basis, shows keloid volume freezing limitations by a single needle and corroborates the observations of minor epidermal and deep dermal damage induced by intralesional cryosurgery.