The influence of wound geometry on the measurement of wound healing rates in clinical trials

Purpose: The comparison of wound healing rates in clinical trials presents a challenging problem. Wound healing typically has been expressed as a change in area over time or a percent change in area over time. These methods are inaccurate, however, when applied to wounds of varying size and shape. A relatively small amount of healing in a large wound will produce a greater change in area than in a smaller wound. Conversely, measurement of the percent change in area of a wound will tend to exaggerate the healing rates of smaller wounds. A method of calculating average linear healing of the wound edge toward the center of the wound has been proposed that should not be influenced by wound size: D = Delta A divided by (P) over bar, where D = linear healing, Delta A = change in area, and (P) over bar = mean perimeter. The purpose of this study was to examine linear healing of the wound edge as a method of measuring wound healing in clinical trials. Methods: We observed 39 patients with venous stasis ulcers. The area, perimeter, length, and width of each wound were calculated with computerized planimetry. Change in area per day and linear healing rate of the wound edge per day were calculated. Multiple linear regression analysis was used to explore factors that influence wound healing as measured by these methods. Results: The change in area per day was significantly and independently influenced by initial area (p < .0001), perimeter (p < .0001), length (p < .00055), and width (p < .0175). Linear healing per day was not influenced by any geometric variable, including area, perimeter, length, width, and ratio of width to length. Conclusion: Linear healing per day is a valid means of comparing wound healing rates in wounds of different dimensions. Linear healing per unit of time should be preferred to measurements of change in wound area to quantify wound healing rates in clinical trials.