Clinical Evaluation of a Wound Measurement and Documentation System

     Abstract: Wound measurement is essential in assessing the progress of wound healing. The most commonly used tools include wound tracings, width and length measurements, and digital photography. These methods have been useful in clinical practice but have some limitations, such as lack of accuracy, difficulty of use, and often entail wound contact. More advanced equipment tends to be bulky, heavy, and expensive. The following reviews the authors’ experience with a new wound measurement and documentation system, the ARANZ Medical Silhouette Mobile™ (ARANZ Medical, Christchurch, New Zealand). This innovative device combines a digital camera and structured lighting in the form of 2 laser beams to automatically correct for image scale and skin curvature, allowing rapid and accurate measurements of the wound surface area and depth. The scanner unit plugs into a standard personal digital assistant to form a portable device that can be easily held and operated using 1 hand. The scanner has been used in clinical practice trials in patients with venous leg ulcers, diabetic foot ulcers, and in the community setting. The scanner was found to be accurate and reliable, easy to learn and use, portable, and compact. The results presented suggest that this device may be a viable choice in the management of different types of chronic wounds.      Accurate and reliable wound measurement is an essential component of wound assessment within clinical practice. Such measurement provides objective data that assists in establishing wound healing progress, alerts the clinician to evidence of deterioration, enhances communication between healthcare providers as well as healthcare providers and patients, aids in the selection of advanced treatment modalities and provides a concise account of the patient’s progress.¹ There is also an increasing demand for practitioners to validate their interventions, thus providing robust rationale to support their practice. Emerging technologies, such as more portable devices with dedicated software are providing healthcare professionals with new tools to support their practice by improving the efficacy of wound measurement and documentation.² Assessment of any wound should begin with the determination of the extent of the area involved. Repeated systematic assessment is required because the extent of a wound is a dynamic process. The total wound extent is based on the wound dimensions and the tissue level involved. The clinical evaluation of the extent of tissue involvement due to a skin lesion and the way a lesion evolves over time are often assessed according to the common sense and memory of the clinician. Evaluations are in general performed based on clinical experience using basic, low-tech equipment to make objective measurements. The determination of the extent of a wound may also be accomplished by noninvasive and invasive technologies. Noninvasive wound assessment includes the measurement of perimeter, maximum dimensions of length and width, surface area, volume, and determination of tissue viability.³      The following introduces the ARANZ Medical Silhouette™ Product Suite (ARANZ Medical, Christchurch, New Zealand), provides preliminary repeatability information for measurements made by the system, and discusses clinical application of the system in different clinical settings.      Hand-held mobile device.The ARANZ Medical SilhouetteMobile™ is a secure electronic, hand-held, noncontact wound measurement and documentation device that is used to accurately measure both wound surface area and depth.^4–6 The device consists of a scanner head that attaches to a standard Personal Digital Assistant (PDA). The scanner comprises a digital camera used to capture an image of the wound and structured lighting that includes 2 fan laser beams. The device’s software runs on the PDA allowing the user to operate the scanner, and performs all the necessary computation at the patient’s side.      The process begins with the user identification on the PDA software via a login procedure, selecting the appropriate patient, and recording the location of the wound on the body. A photographic image of the wound is taken to capture the wound surface area. The operator traces the wound margin on the image displayed on the PDA’s touch screen using the PDA stylus (Figure 1). The structured lighting enables a 3-dimensional model of the patient to be created, thereby compensating for the skin curvature; the distance and orientation of the camera from the wound and scale and perspective distortions in the image. An unwrapped or morphed photographic image is then created, akin to unwrapping the anatomy onto a flat surface, thus enabling an accurate and repeatable measurement of surface area to be made (Figure 2). Wound depth is captured by a second image where the laser beam is repositioned along the wound base with the profile of depth through the wound being recorded by the system (Figure 3). The system then computes wound volume from the measurements of wound surface area and wound depth. As historic data from earlier assessments are stored on the PDA, the results from the current assessment can be compared to those of the previous assessments in the form of a graph showing progress over time.      The software produces a comprehensive report containing digital images of the wound, wound measurements (surface area, depth, and volume), a graph of changes over time, and progression notes recorded on the wound assessment tool. The report can then be downloaded into the patient’s electronic notes or printed for filing in paper notes.      The practicalities of equipment in the clinical setting require that they are efficient and user friendly in order for them to be adopted. The device is easy to operate and can be easily transported in both hospital and community settings. It also provides immediate clarification of wound progress in the form of graphs and a standardized wound assessment tool.      Once data are collected on the PDA, it can be transferred (ie, downloaded or synchronized) to a database on the clinic’s computer network. The included software tool performs the synchronization function and stores all the information in a secure database. The software tool also transfers information pertaining to any patient to the PDA that may have been collected by another user on a different PDA or entered into the system through a web interface. Thus, patient information is seamlessly transferred between users (Figure 4).      System repeatability. The mobile device was used to collect wound planimetry in 30 patients affected by venous leg ulcers attending the wound healing outpatient clinic at the Department of Dermatology of the University of Pisa. To estimate the repeatability and the reproducibility of wound assessment, 2 female nurses participated in this study. The intra- and inter-rater reliability of measurement were observed using intra-class correlation coefficients (ICC) and Bland-Altman test.

Results

     The measured total areas and volumes for independent raters and for subsequent measures of 1 rater are displayed in Table 1. No statistically significant differences were found between scans evaluated by the 2 investigators about wound area and volume. The relative error and the intra-class correlation coefficients are shown in Table 2. The ICC values were excellent either for intra- or inter-rater reproducibility with a very low relative error value. The intra- and inter-rater measurement demonstrated its reliability as indicated by high ICC values (> 0.80). The mean ± SD time for a full scan acquisition on the wound area and depth was 2.6 ± 1.2 minutes.      Clinical use in the community setting. The Wound Care Specialist service at Nurse Maude (Christchurch, New Zealand) serves a population of approximately 400,000. The multidisciplinary team to improve outcomes for chronic nonhealing wounds.      The device is used within the service to capture data and monitor progress within the 4 clinics, and can be employed in the patient’s home.      The following case demonstrates how immediate, objective data can benefit the patient and improve outcomes.      Ms. K, age 33, was referred for specialist wound assessment of a Grade IV sacral pressure ulcer. She sustained the wound during a holiday overseas 9 months earlier and has since had a District Nurse (Home Care Nurse) visiting to re-dress the wound using vacuum- assisted therapy.      Ms. K has tetraplegia caused through a motor vehicle accident 5 years previously. She lives in her own home with 24-hour care support. Despite her bed rest, an alternating airwave mattress, and frequent turns, the wound was failing to progress at the expected rate causing Ms. K to become frustrated and angry.      On assessment the main factors affecting healing were identified as her severe frustration, inadequate pressure relief and inadequate intake of protein. The wound appeared dull and odorous suggesting heavy bacterial colonization, and was measured with the mobile device (Figure 5). Ms. K explained she was unable to tolerate bed rest and felt it had a minimal effect toward her healing.      The heavily colonized wound was managed with a topical antimicrobial dressing, in the form of a silver contact wound layer, applied beneath the negative pressure dressing. It was agreed fortnightly wound measurements would be recorded. The management plan would be reviewed if progress was not maintained.      Four weeks later the wound had shown significant improvement. The mobile device provided objective data for both patient and nurse demonstrating a reduction in depth and the objective proof Ms. K needed to support her continuation with the treatment plan.      The report showing surface area, depth, and the graphed progress enabled both the nurse and Ms. K to pinpoint changes in her care. In one instance, over the course of a week Ms. K significantly increased the time she spent sitting at the computer, corresponding with an increased depth of the wound. This objective data resulted in concordance with the plan of care.      Since using the mobile device, Ms. K states that she feels more involved and has control of her care enabling her to work in partnership with the nursing team. Using the photographs and progress graphs she can make informed decisions in relation to her activities of daily living.      Clinical use in diabetic foot clinic. The diabetic foot clinic or wound healing center is a specialized center where all aspects of the ulcer can be managed with advanced techniques and in a multidisciplinary setting. There are many products available to treat wounds at varying stages and some are quite costly. To adequately determine if a product or device is improving, precise wound measurements must be documented at each visit. Many centers use “standard of care” treatment protocols for the first 4 weeks to determine the need for advanced products. If the wound fails to heal by 50% area in 4 weeks, it has a 91% negative predictive value of healing at 12 weeks.⁷ In these particular cases, more advanced and expensive products are necessary. This emphasizes the importance of accurate wound assessments. Manual length x width measurements of wounds are not accurate. Length x width assessments are mathematically accurate for measuring the area of a square, but not a circular or otherwise irregularly shaped wound.      The mobile device product suite offers the diabetic foot clinic the ability to accurately measure wounds, chart progress on a graph, manage/store data, and print reports. These enhancements can improve appropriate utilization of advanced products and outcomes.      Patient A has an uninfected, nonischemic plantar diabetic foot ulcer that received regular debridement and appropriate offloading. In 4 weeks this ulcer decreased in size from 4.8 cm2 to 1.1 cm² (78%). In this case, the wound was predicted to heal within 12 weeks, at which point the current treatment would be continued (Figure 6).      Patient B has diabetes and a venous leg ulcer. The ulceration initially decreased in size over 2 weeks, but then stagnated for the following 2 weeks. This would require a change of treatment to attain wound closure (Figure 7).      The mobile device allows wound-healing professionals to noninvasively track wounds and direct advanced treatments to wounds that would not heal with standard care alone, thus conserving costs to the healthcare system and diabetic foot clinic.

Discussion

     Over the years, there have been numerous applications of technology attempting to perform measurements of the wound, utilizing both off-the-shelf and custom-made 3-dimensional scanning equipment or range-finding cameras.^8,9 While many such solutions may be appropriate for users performing research, for routine clinical use, such systems are too complex, cumbersome, and expensive.¹⁰ With this mobile device there is no need to transfer data from the image capturing equipment to a computer in order to perform the wound measurements. Instead, the user interaction is done immediately following image capture on the hand-held PDA, and results can be obtained immediately. Therefore, simultaneous measurements can be obtained easily as well. Furthermore, the hand-held unit is small, lightweight, and is relatively inexpensive. Another common approach to the wound measurement is photographic-based digital planimetry, involving scaling a photographic image based on the identification of a known target such as a ruler, which is visible in the photograph.¹¹ Such techniques influence various assumptions such as the wound lies in a plane, that the photograph was captured with the camera lens perpendicular to the wound, or that the target is in the plane of the wound.¹² Deviations from these assumptions can introduce significant errors.¹³ The device’s structured lighting, in the form of 2 laser planes, help correct for the position and orientation of the digital camera from the wound. Furthermore, they are used to build a 3-dimensional model of the underlying anatomy, thereby overcoming the limitation of assuming the wound is in a plane, which is an inherent limitation of photo planimetry.

Conclusion

     The hand-held scanner device was found to be reliable and easy to use. Its portability and accuracy lend itself to quick assessment of wound size and for tracking wound-healing progress. The results presented suggest that this device may be a viable choice in the management of different types of chronic wounds.