Current Methods of Measuring Ulcers. A Review

Abstract

Following a critique of the literature concerning two-dimensional and three-dimensional measurement of ulcers, the authors describe an interrater and intrarater reliability study on linear measurement of an ulcer. Analysis of the results infers that neither method is reliable.

Accurate and repeatable methods of recording the size and shape of ulcers would enable clinicians to record treatment progress. However, from the literature there seems to be no consensus as to the most valid and reliable means of measuring plantar ulcers. The purpose of this study was to review current literature of measuring methods of ulcers in an attempt to determine a good practice method for practitioners. A pilot study was performed to ascertain interrater and intrarater reliability of linear measurement of the plantar ulcer.

Background

Methods used to measure ulcers can be divided into two categories, ie, two-dimensional and three-dimensional methods. The former can be divided into the tracing method and the photographic method. Griffen et al. [1] described a tracing technique where ulcer margins were outlined onto a transparency sheet using an indelible pen. The surface area of the ulcer was calculated using a digitizer interfaced with a computer. Cutler et al. [2] traced the ulcer margins onto a piece of plastic sheet; then using a planimeric device, calculated the surface area of the lesion. A further modification to the methodologies above was described by Etris et al. [3].

Using a transparency tracing, an x-ray film was made and the plate scanned using a planar morphometry program. Griffen et al photographed the ulcer, then outlined the margins on a projected slide. Using computer digitization and planimetry, the surface area of the ulcer was calculated. Cutler et al. described similar methodologies. No one method was considered superior when measuring two dimensions of the ulcer. Linear assessment also failed to measure depth and volume.

Johnson [4] described the three-dimensional volumetric method. A graduated swab stick was placed into the base of the ulcer through a sheet of plastic flush with the skin’s surface. The volume of the ulcer was calculated using a mathematical formula. A major potential source of error reported was the tendency to place the swab stick in a different area of the ulcer’s base. This was considered to give a false representation of the healing rate of the ulcer.

Plassman et al. [5] described three other volumetric measurements. The saline method involved injecting saline solution through a transparent, elastic film. The fluid was injected with a calibrated syringe and the amount of saline needed to fill the cavity was considered a direct measure of the ulcer’s volume. A second technique described required casting the cavity of the ulcer with impression material. The volume of the ulcer was calculated by either multiplying the weight of the impression by its density, or measuring the water displaced in a graduated cylinder. The authors were critical of the saline technique and believed accuracy was compromised, especially if the ulcer surface absorbed saline or the practitioner was unable to level flush to the previous skin structure. Disadvantages of the impression method were the tendency to overfill the cavity and the physical difficulty of producing a smooth surface to the skin. Concerns were also expressed about the ethics of disturbing healing membranes; however, the authors did consider this method the most preferable.

Another method used to measure the size and depth of an ulcer was the image-processing method that used a projector to illuminate sensitive skin strips laid over the ulcer surface. A digital camera detected contours and produced a computer-generated three-dimensional representation of the skin surface. Digital pictures could be stored and used for later reference. While this technique was considered the most reliable, it had limitations when used to measure deep and large ulcerations.

Methodology

A pilot study was performed to ascertain the interrater and intrarater reliability of linear measurement. Six raters were required to measure the linear distance across a photographed ulcer six times. To avoid unethical risks, assessment of an actual ulcer was eliminated by using a life-size photograph of a venous ulcer located distal to the medial malleolus. Raters were required to use a metric ruler to measure to the nearest half millimeter the widest and longest dimensions of the presenting ulcer. Each subject repeated the measurements at three intervals each day for 2 days. Data on the record sheet were concealed to circumvent subjects from rerecording previous measurements.

Results

Using analysis of variance, both interrater and intrarater reliability were poor (

Table 1. Analysis of Variance for Measurement and Width of the Ulcer. 

).

Discussion

From the literature, there seems to be no consensus as to the most valid and reliable means of measuring plantar ulcers. While linear measurement may be easy to perform in the clinical setting according to this pilot study, the technique is unreliable. The findings of this study were constant with the literature reviewed. Linear techniques also fail to record depth and volume of lesions, which may provide critical information. Other common methodologies used to measure were reviewed and the general consensus was that no one method was accurate, repeatable, or reliable. All methods provide clinicians with some information concerning the ulcer’s dimension. However, with regard to a good practice method, the authors recommend collecting a wider range of data other than linear measurement alone. In conclusion, the authors acknowledge the need for further study into methods of measuring ulcers.