Comparison of two devices for the treatment of keloid scars with the use of intralesional cryotherapy: An experimental study.
BACKGROUND
Intralesional (IL) cryotherapy is a new technique for the treatment of keloid scars, in which the scar is frozen from inside. Two cryodevices are available, which were recently evaluated. Both devices showed promising results, but differed in clinical outcome. To explain these differences, more understanding of the working mechanism of both devices is required.


OBJECTIVE
This experimental study was designed to investigate and compare the thermal behavior of an argon gas- and a liquid nitrogen-based device. Thermal behavior constitutes: (1) minimum tissue temperature (°C), (2) the freezing rate (°C/min). The thermal behavior was measured inside and on the outer surface of the scar. Both devices were tested ex vivo and in vivo.


RESULTS
Ex vivo, when determining the maximum freezing capacity, the argon gas device showed a higher end temperature compared to the liquid nitrogen device (argon gas: -120°C, liquid nitrogen: -140°C) and a faster freezing rate (argon gas: -1300°C/min, liquid nitrogen: -145°C/min). In vivo, measured inside the keloid, the argon gas device showed a lower end temperature than the liquid nitrogen device (argon gas: -36.4°C, liquid nitrogen: -8.1°C) and a faster freezing rate (argon gas: -14.7°C/min, liquid nitrogen: -5°C/min). The outer surface of the scar reached temperatures below -20°C with both devices as measured with the thermal camera.


CONCLUSIONS
In conclusion, the argon gas device displayed a lower end temperature and a faster freezing rate in vivo compared to the liquid nitrogen device. Although this resulted in lower recurrence rates for the argon gas device, more hypopigmentation was seen compared to the liquid nitrogen device following treatment. Finally, the low outer surface temperatures measured with both devices, suggest that some hypopigmentation following treatment is inevitable.
Department of Plastic and Reconstructive Surgery, VU University Medical Center, Amsterdam, The Netherlands. Electronic address: mc.vanleeuwen@vumc.nl.
Michiel C E
MC
van Leeuwen
Department of Plastic and Reconstructive Surgery, VU University Medical Center, Amsterdam, The Netherlands.
Anne Eva J
AE
Bulstra
Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.
A J
AJ
van der Veen
Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.
W B
WB
Bloem
Department of Surgery, VU University Medical Center, Amsterdam, The Netherlands.
P A M
PA
van Leeuwen
Department of Plastic and Reconstructive Surgery, VU University Medical Center, Amsterdam, The Netherlands.
F B
FB
Niessen
D016115:Albinism, Oculocutaneous / Q000209:etiology; D001128:Argon / Q000627:therapeutic use*; D017679:Cryotherapy / Q000009:adverse effects / Q000295:instrumentation*; D005615:Freezing; D006801:Humans; D017496:Hypopigmentation / Q000209:etiology; D007627:Keloid / Q000628:therapy*; D009584:Nitrogen / Q000627:therapeutic use*; D016896:Treatment Outcome
D001128:Argon; D009584:Nitrogen
Argon gas; Cryosurgery; Intralesional; Intralesional cryotherapy; Keloid scars; Scar treatment