The use of smartphone thermography to more safely unmask and preserve circulation to keystone advancement flaps in the lower extremity.

[BACKGROUND] The keystone perforator flap is a simple, popular form of advancement flap that can solve many defects of the lower extremity that can avoid consideration of a microsurgical tissue transfer. The actual circulation to this local flap subtype has not yet been delineated. The recent introduction of inexpensive thermal imaging cameras that can be coupled with a SmartPhone allows thermagrams of these flaps where "hot spots" are known to correspond to the location of pertinent perforators that will provide the requisite flap vascularization.

[METHODS] Over the past year, 10 patients were considered for a keystone flap of the lower extremity in lieu of a skin graft or free flap. All patients had a "cold challenge" or thermal stress followed by a thermal recovery recorded by serial thermography to determine perforator "hot spot" location as well as their absence or "cold spots." Flaps were designed and harvested according to these findings.

[RESULTS] In one patient, inadequate "hot spots" were found in all adjacent donor regions that could have allowed a keystone flap alternative. Instead, more safely a skin graft was done. The other 9 patients had 10 flaps. Intra-operative thermagrams predicted 100% flap survival for 9 flaps and marginal ischemia for 1 flap, and was a correct assessment in all cases. Dehiscence occurred in the latter flap that healed by secondary intention, while the rest healed uneventfully.

[CONCLUSION] The use of the SmartPhone for thermography is a simple, rapid, cheaper means for the evaluation of viability of keystone flaps in all surgical phases. This provides a safe method for checking not only flap circulation, but also identification of "cold spots" or flap regions where means to augment advancement by deep fascia interruption or undermining will not interfere with flap perfusion. There is virtually no learning curve in acquiring the skills to use this device, which should now allow anyone to raise actually any kind of local perforator flap as they find suitable.