Cryotherapy models provide valuable information for the treatment of skin warts

Viktor A. Zouboulis1, Christos C. Zouboulis2

1MINT Grün student, Technical University Berlin, Berlin, Germany
2Departments of Dermatology, Venereology, Allergology and Immunology, Dessau Medical Center, Dessau, Germany

One of the most common and effective methods used in the treatment of warts is cryotherapy. The present study investigated the validity of cryotherapy models on predicting the effectiveness of the procedure on skin warts. Two small commercial cryotherapy devices (units A and B) were administered for 10"-60" on tomatoes and potatoes heated to local human skin temperature and used as skin wart models. Frozen surface and depth were evaluated by standardized photography and computer analysis. Tissue temperature at depths of 0.1-10 mm was assessed during treatment by an electronic thermometer. Cryotherapy induced a transient freezing of the tomato surface. The devices produced similar tomato tissue temperature reduction at all depths examined. At 5 mm, unit B induced lower tissue temperatures than A. Both devices induced potato tissue destruction to a depth of 0.5-1.2 mm at 40” and 50”. Unit A induced a maximum destruction at 40”, unit B led to a partially linear destruction depth with freezing time. The devices produced similar reduction of potato tissue temperature at all depths tested. Unit A induced more rapidly lower temperatures (1.5 mm, 10”, p=0.001). Unit B induced lower tissue temperatures with time (0.1 mm, 50”, p=0.025; 60”, p=0.039; 5 mm, 60”, 0.05). None of the devices reached the lethal temperature of -22°C. Both cryotherapy devices produced sufficient tissue damage, at least in the potatoes, to a depth of 0.5-1.2 mm when applied for 40”, which is the commercially proposed treatment time. In conclusion, the selected models were found to be valid for the prediction of the effectiveness of cryotherapy devices on skin warts.