title: Effect of skin surface temperature on skin pigmentation during contact and intralesional cryosurgery of keloids.
abstract: BACKGROUND
  This 15-month study was designed to compare the effect of skin surface temperature on skin pigmentation following a single intralesional or contact cryosurgical treatment of keloids.
  
  
  METHODS
  Thirty Caucasian patients with 45 keloids present for more than 6 months were included in this study. Twenty-one keloids were treated by the contact method while the remaining 24 scars were managed using an intralesional cryosurgery technique. The skin surface temperature at the keloids was measured and recorded using a Ni/Cd thermocouple. Four variables of the thermal history were evaluated with the contact and the intralesional methods, namely cooling rate, hold time, end temperature and thawing rate. Assessment of the local hypopigmentation was performed 6 months after the treatment using a pigmentation scale.
  
  
  RESULTS
  Significantly slower cooling (6.09 +/- 4.56 degrees C/min) and thawing rates (54.52 +/- 32.17 degrees C/min) were recorded with the intralesional cryosurgery method when compared with the cooling rates (13.47 +/- 9.04 degrees C/min) and thawing rates (89.00 +/- 86.42 degrees C/min) of the contact method (P < 0.000001). The end temperature of the contact technique was significantly cooler (-46.77 +/- 14.74 degrees C) when compared with that of the intralesional method (-15.55 +/- 6.77 degrees C) (P < 0.000001). There was a trend for the hold time of intralesional cryosurgery to be longer (82.67 +/- 138.03 s) than that of the contact method (16.86 +/- 23.49 s) (P < 0.059). A significant difference in skin pigmentation was demonstrated between the two cryosurgical methods. In 91.7% of the keloids treated by the contact technique a significant hypopigmentation was noticed, while no marked hypopigmentation was detected in the skin surface of the keloids treated by the intralesional method (P < 0.0001).
  
  
  CONCLUSIONS
  We hypothesize that the thermal history of the skin surface during the intralesional cryosurgery technique provides a better survival environment for the melanocytes than the contact method, thus producing a lower rate of permanent hypopigmentation and disfiguring.
authors.affiliation: Department of Plastic Surgery, Linn Medical Center, The Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel. yaron07@yahoo.com
authors.forename: Y
authors.initials: Y
authors.lastname: Har-Shai
authors.forename: E
authors.initials: E
authors.lastname: Dujovny
authors.forename: E
authors.initials: E
authors.lastname: Rohde
authors.forename: C C
authors.initials: CC
authors.lastname: Zouboulis
mesh_terms: D000328:Adult; D003452:Cryosurgery / Q000379:methods*; D005260:Female; D006801:Humans; D017496:Hypopigmentation / Q000209:etiology / Q000517:prevention & control; D007627:Keloid / Q000601:surgery*; D008297:Male; D012880:Skin Pigmentation; D012881:Skin Temperature; D018709:Statistics, Nonparametric