Each method of wound area measurement has its own strengths and weaknesses. According to a prospective, comparative trial22 of hand measurements using standardized wound models with known area, hand measurements are fast, inexpensive, and can accommodate circumferential wounds, but they are also inaccurate, imprecise, and risk contamination of the wound. In addition, the many ways to measure wound area by hand adds to the imprecision. Some practitioners multiply the largest length and width of the wound regardless of orientation, while others take the longest length and the longest perpendicular width; the longest width head-to-toe and the longest width side-to-side also can be measured.22 All of these methods overestimate wound area because they assume that wounds are perfect squares or rectangles.22 A retrospective analysis23 of 2768 wounds demonstrated that hand measurements overestimated wound area by 44%. Large wounds and irregularly shaped wounds exacerbate the inaccuracy.3 This measurement technique is considered to be simple but not very reliable for irregular or large wounds.3 Although research is limited in this area, it seems plausible that when patients have irregular wounds, hand measurements may be insufficient to accurately measure percent area reduction.
Acetate tracing is another low-tech method of wound measurement. A 2-layer, transparent sheet with a square centimeter grid is placed on top of the wound, and the border is traced; the area inside the border then can be calculated by square counting.24 Digital planimetry works the same way but requires retracing the wound onto a tablet computer, which then calculates the wound area.24 The advantages of this system are relatively accurate and precise wound measurements. However, it can be a time-consuming procedure, and the results can vary slightly based on the subjective interpretation of the wound border, the use of excessively thick markers, or the use of too much pressure on the wound, which can alter the outline.24 Additionally, according to literature reviews,8 acetate tracing may damage or contaminate the wound bed and may be painful.
In noncontact planimetry, a target scale is placed in the same plane as the wound and a high-resolution photo is taken, after which specialized software analyzes the wound area based on the captured image.8 In a comparative trial25 of digital planimetry versus contact tracing of 11 shapes using 4 observers, the 2 techniques demonstrated similar wound measurement accuracy with a correlation coefficient of >0.8. Although noncontact planimetry is clinically expedient in comparison to contact planimetry, it has limitations. The technique cannot account for the natural curvature of the body, subjecting larger wounds to inaccuracies, and in larger circumferential wounds, the entire wound may not be able to fit within the confines of a single photograph.8
Laser-assisted wound measurement devices are relatively new but attempt to improve upon noncontact planimetry by using both a digital camera and projected laser beams. This allows measurement of the curvature, depth, and irregularity of a wound surface. An initial picture is taken, and the operator outlines the wounds. The system then can calculate wound area and volume. The laser device used in the current analysis has been validated (average interclass correlation coefficient of 0.988) for interrater reliability in a study17 of 7 nurses involved in wound care. The device’s measurements also were validated for wound area and wound volume in 12 wounds on a porcine model18 and for area and volume measurements on clay models of diabetic wounds.16 It also has been trusted for multiple Phase I to Phase IV clinical trials, including multicenter and multinational studies.15 Laser-assisted measurements have distinct benefits: they have the potential to be more accurate than noncontact planimetry because they take into account the curvature of the body and can measure both wound volume and area.8 However, the overall process is more time consuming than hand measurements and requires bulky peripherals such as the laser device itself and computers for assessment. Additionally, this device is not able to calculate circumferential wounds because the entire wound cannot fit within the confines of a single photograph.
The 3D wound measurement device used in this study has been validated in artificial wound models, animal models, and diabetic foot ulcers12-14 but had not been examined for use in other wound types. The interrater reliability of the device is considered to be high; in a study by Anghel et al,12 45 wounds were previously assessed by 2 raters using the 3D device with an interclass correlation coefficient of 0.998 for wound area.
In the current study, both devices showed significant differences in area in comparison to hand measurements in a patient population with multiple wound etiologies including pyoderma gangrenosum, venous leg ulcers, diabetic foot ulcers, and traumatic ulcers. This is not surprising given the anecdotally high level of inaccuracy of hand measurements. No significant difference was found between the measurements obtained using the 3D device and the laser device, suggesting the 3D device exhibits similar accuracy for wound measurement in comparison to laser devices in a clinical setting.
This accuracy is important in the clinical setting because wounds with irregular borders are difficult to measure accurately with hand measurements, making calculations of percent area reduction unreliable. Additionally, the 3D device is quick and efficient in clinical settings. Anecdotally, the device was found to have a friendly user interface that requires minimal training. Instead of outlining the wound directly, the user simply needs to broadly circle the wound so the software can algorithmically determine healthy versus wound tissue. This process anecdotally is fast in comparison to noncontact planimetry or laser devices. Previous wound measurements are easily accessible to trace the patient’s progress over time. Additionally, the information can be automatically synced with the product’s HIPAA-compliant cloud server, allowing the physician to access this data anywhere. Another advantage is mobility; a clinician can carry the tablet in a lab coat to each clinical encounter. However, the 3D device has important limitations. It captures a single image so it is unable to measure large circumferential wounds. Additionally, the device cannot take into account wounds with significant undermining. In cases of wounds with substantial undermining, various hand measurement techniques can be used to determine undermining depth.