Undermining during cutaneous wound closure for wounds less than 3 cm in diameter: a randomized split wound comparative effectiveness trial

Undermining is thought to improve wound outcomes; however, randomized controlled data regarding its efficacy are lacking in humans. The objective of this randomized clinical trial was to determine whether undermining low to moderate tension wounds improves scar cosmesis compared to wound closure without undermining. Fifty-four patients, 18 years or older, undergoing primary linear closure of a cutaneous defect with predicted postoperative closure length of ≥ 3 cm on any anatomic site were screened. Four patients were excluded, 50 patients were enrolled, and 48 patients were seen in follow-up. Wounds were divided in half and one side was randomized to receive either no undermining or 2 cm of undermining. The other side received the unselected intervention. Three months, patients and 2 masked observers evaluated each scar using the Patient and Observer Scar Assessment Scale (POSAS). A total of 50 patients [mean (SD) age, 67.6 (11.5) years; 31 (64.6%) male; 48 (100%) white] were enrolled in the study. The mean (SD) sum of the POSAS observer component scores was 12.0 (6.05) for the undermined side and 11.1 (4.68) for the non-undermined side (P = .60). No statistically significant difference was found in the mean (SD) sum of the patient component for the POSAS score between the undermined side [15.9 (9.07)] and the non-undermined side [13.33 (6.20)] at 3 months. For wounds under low to moderate perceived tension, no statistically significant differences in scar outcome or total complications were noted between undermined wound halves and non-undermined halves. Trail Registry: Clinical trials.gov Identifier NCT02289859. https://clinicaltrials.gov/ct2/show/NCT02289859.