At what diameter does a scar form after a full-thickness wound?

DENVER – A clinically identifiable scar occurs after full-thickness skin wounds greater than 400-500 mcm in diameter, while wounds of smaller diameter heal with no clinically perceptible scar.

Dr. Amanda H. Champlain

The findings come from a small pilot trial that set out to determine the biopsy size limit at which healing occurs without a scar, as well as demonstrate the safety of performing multiple skin microbiopsies. “The broader purpose of this work is to contribute to the development of techniques for harvesting skin tissue with less morbidity than conventional methods,” lead study author Amanda H. Champlain, MD, said in an interview in advance of the annual conference of the American Society for Laser Medicine and Surgery. “The size threshold at which a full-thickness skin wound can heal without scarring had not been determined prior to this study.”

Dr. Champlain, a fellow at Massachusetts General Hospital and The Wellman Center for Photomedicine, both in Boston, and her colleagues designed a way to evaluate healing responses and safety after collecting skin microbiopsies of different sizes from preabdominoplasty skin. According to the study abstract, the concept “is based on fractional photothermolysis in which a multitude of small, full-thickness thermal burns are produced by a laser on the skin with rapid healing and no scarring.” Measures included the Patient and Observer Scar Assessment Scale (POSAS), donor site pain scale, subject satisfaction survey, and an assessment of side effects, clinical photographs, and histology.

Preliminary data are available for five subjects. The POSAS-Observer scale ranges from 5 to 50 while the POSAS-Patient scale ranges from 6 to 60. The researchers observed that average final POSAS-Observer scores were 5.6 for scars 200 mcm in diameter, 5.2 for scars 400 mcm in diameter, 7.0 for scars 500 mcm in diameter, 6.8 for scars 600 mcm in diameter, 8.2 for scars 800 mcm in diameter, 9.6 for scars 1 mm in diameter, and 13.2 for those 2 mm in diameter. Meanwhile, the average final POSAS-Subject scores were 6.0 for scars 200 mcm in diameter, 6.0 for scars 400 mcm in diameter, 6.6 for scars 500 mcm in diameter, 6.4 for those 600 mcm in diameter, 7.2 for scars 800 mcm in diameter, 7.4 for scars 1 mm in diameter, and 10.0 for those 2 mm in diameter.

The maximum donor site pain reported was 4 out of 10 in one subject. “The procedure was very well tolerated by the subjects,” Dr. Champlain said. “They healed quickly, and the majority were happy with the cosmetic outcome regardless of the diameter of the microbiopsy used.”

The most common side effects of the study procedures included mild bleeding, scabbing, redness, and hyper/hypopigmentation. “The majority of study participants strongly agree that the study procedure was safe, tolerable, and cosmetically sound,” she said.

Dr. Champlain does not have any disclosures, but she said that the study was funded by the Department of Defense.

dbrunk@mdedge.com