How to Measure a Wound: A Quick Guide

Accuracy in wound measurement is important, as it helps practitioners determine the type of treatment needed and if a wound is healing. However, you might be surprised to learn that the measurement error rate is around 44%, ultimately leaving patients vulnerable to adverse and costly complications. Factors like a provider’s experience, the tools they use, and even the wound shape play a role in what measurement one comes up with and the clinical decisions one makes. 

Because inconsistent measurements can have undesirable results, we wanted to take a deep dive into how to measure a wound. In this wound measurement guide, you’ll discover the different measurement methods used, why measuring is essential, and more. 

What Is Wound Measuring? 

The answer to this question seems self-explanatory, right? Even someone who doesn’t work with wounds would probably describe it as a technique used to identify the precise size of an injury, and they’d be correct. However, this explanation just scratches the surface. 

Measurement of a wound involves examining its length, width, and depth, and it’s an important factor in diagnosing and treating wounds. This is a key component of the initial assessment, giving clinicians a baseline of the wound’s state. Although other components of the assessment, like the type of wound, its location, color, and degree of injury, are essential, a wound care specialist must observe the size to make informed decisions. 

Wound measuring remains an integral action when completing reassessments at regular intervals. It’s also one of the first steps taken when a wound has seemingly changed in appearance or odor. 

Why Is Measuring a Wound Important? 

Now that we’ve established what wound measuring is, let’s discuss why it’s so important. 

Healing Progress Indicator

One of the main reasons skilled practitioners measure wounds is to monitor a patient’s wound journey. Measurement is one of the most objective tools used during wound assessments, giving providers a quantifiable way to monitor progress (as opposed to qualitative measures, like color and odor). Clinicians can consistently review a wound’s measurements and compare them to different time points, even across multiple healthcare professionals. The measurements obtained during each assessment can tell providers if the wound is static, worsening, or healing. 

Guides Plan of Care and Monitors Treatment Effectiveness 

Regularly monitoring the size of a wound also reveals the efficacy of the current treatment protocol and gives practitioners an idea of the rate of healing. This vital information, in turn, guides clinicians when developing a patient-centered care plan, allowing them to establish more realistic short- and long-term goals. They can use this data to predict if the wound is unlikely to heal with traditional therapies and adjust accordingly. 

For instance, calculating the percentage change in wound surface area is recommended for determining therapy effectiveness. Research suggests that advanced therapy should be initiated if the wound surface area hasn’t decreased by 50% or more in four weeks of standard treatment. It’s also stated that a reduction of wound surface area by 10% to 15% in a week is useful in estimating the probability of wound closure. 

As one study shared, “Wound size and area are useful predictors of the final outcome.” So, whether a patient comes in with a laceration, abrasion, or something else, wound measuring should be completed.

Quality Measures and Reimbursements 

Wound measurements are central to improving patient health outcomes, but they also tie into the overall success of healthcare institutions. 

Let’s take the Merit-Based Incentive Payment System (MIPS), for example. The Centers for Medicare and Medicaid Services (CMS) created it to boost care quality and decrease the cost of Medicare care delivery. Wound care practitioners can earn a positive performance-based payment adjustment for their Medicare claims by participating and performing well. However, doing poorly could also lead to financial penalties. 

An outcome measure, like Diabetic Foot Ulcer Healing or Closure (USWR33), for instance, measures the percentage of diabetic foot ulcers among patients aged 18 or older that have achieved healing or closure. Wound measurements must be performed to monitor this, so performing them correctly is ideal. 

How to Measure a Wound: Traditional Techniques 

There’s more than one way to measure a wound, ranging from simple methods with disposable rulers to advanced practices utilizing computer software. We’ll go over some of the most common wound measurement examples below. 

The Length and Width Approach

Probably one of the easiest measuring methods, this technique entails measuring the length and width of the wound in centimeters and then multiplying it to capture the surface area. However, you’ll want to keep in mind that the results may differ depending on where you take the measurements. Usually, clinicians do one of the following:  

• Calculate the longest length x greatest width at any angle to each other or, 
• Multiply the longest length by the greatest width, perpendicular to each other .

Another thing to remember is that this approach is most practical for rectangular or square-shaped wounds. Yet, as you know, most wounds have an irregular shape. It’s worth keeping in mind that you could end up overestimating the total surface area using this approach. 

The Clock Method

Also called linear measurement, this approach may involve using a disposable paper centimeter (cm) ruler and swab to measure the length and width of the wound. Want to measure a wound in cm even more effortlessly and with fewer tools? There are plastic probes that are pre-marked with centimeter (cm) markings available. 

To start, the patient should be in a neutral position. With the clock face as a reference, the practitioner should ensure that the patient’s head is positioned at 12:00 and their feet at 6:00, also called head-to-toe. To determine the length, measure the wound using the 12:00 to 6:00 axis while measuring the width side-to-side or the 3:00 to 9:00 axis. Measure from the wound edge to the opposite wound edge at the longest point for both length and width. 

Depth must also be captured and is often done using a pre-moistened and sterile cotton-tipped swab. A clinician should insert the swab into the wound’s deepest area perpendicular to the skin’s surface and grasp it where it meets the wound margin or edge. Following that, place it against a ruler for measurement. 

Measure Undermining and Tunneling

Make a point to assess the wound area for undermining and tunneling, too. For both, you can use the clock face to determine the direction and location of the wound.

As a refresher, undermining is when the wound edges have separated from the surrounding healthy tissue, causing it to erode and form a pocket under the wound’s surface. To assess for undermining: 

• Insert the swab’s tip right under the wound edge. 
• Hold the swab nearly parallel to the wound surface, and pause when you feel resistance. 
• The amount of undermining is the distance from the swab tip to the point at which the swab is level with the wound edge.  
• You might document it as “undermining observed along the wound perimeter from 1 to 4 o’clock. At 1:00 to 3:00, it’s 2.5 cm; at 4:00, it’s 3.5 cm.”

Tunneling occurs when narrow pathways form that go from the skin’s surface into deeper layers of tissue. To measure it: 

• Carefully insert the swab into a pathway until you feel resistance.
• Determine the depth by measuring the distance from the tip of the swab to the point where it is level with the wound edge. 
• This could be documented as a “4 cm tunnel at 9:00.” 

The Tracing Technique

If a wound has very irregular edges, it might make more sense to use the tracing method. With this approach, a clinician places an acetate sheet or transparent film over the wound. Usually, there are two layers, one of which can be thrown away and the other placed on a grid. Then, a pen or fine-tipped permanent marker is used to trace the perimeter. Once you’re complete, you’ll have a template that’s easier and more precise to measure off the body. 

However, this technique can make it difficult to pinpoint the wound margins, especially where exudate is present. Subjectivity is introduced, which can make measurements less accurate. 

Tracing isn’t as common today because they’re not easily scanned into electronic health records (EHRs). It was much more prevalent when the industry relied heavily on paper-based records. 

Photo Documentation 

Typically used as an adjunct to measurement, practitioners occasionally take photos to monitor progress and record wound assessment. However, these images aren’t as valuable without measuring the wound. Therefore, it’s essential to include a ruler when taking the photos. Photography allows clinicians to view a wound’s size objectively, although this approach can’t correctly measure depth. 

Obtaining images helps the care team collect vital information about the injury, such as the condition of the surrounding skin and tissue type. However, consistency is important. 

Every practitioner should take the photo at the same distance from the wound during each assessment and keep the patient in the same position. Everyone should be using the same angles, lighting, and more for the most accurate insight.

The Future of Wound Measuring: Image-Based AI

Technological advancements have changed the way clinicians manage wounds. Instead of performing those time-consuming manual wound measurement examples mentioned above, advanced imaging technology powered with artificial intelligence (AI) can streamline tasks so providers can more efficiently handle their workload. 

Let’s look at 3D imaging for a moment. Specialized cameras can obtain wound topography, allowing clinicians to gain length, width, and even depth measurements without much physical contact with the patient. In fact, wound care specialists can review these images and make treatment decisions without them even being in the same location as the patient. For instance, a home health provider could take the picture, and someone at a clinic could review the wound as if they were there. That’s because digital imaging tools allow them to toggle around, zoom in, and achieve a more comprehensive view. 

As you might imagine, this is more comforting for patients, especially those with painful, complex wounds. It also minimizes the risk of wound contamination. Now, just imagine the potential when AI is added to the mix. 

The Influence of AI on Wound Care

When 3D imaging is paired with AI, it has the potential to improve care outcomes significantly. As one study noted of current methods, “[Wound] assessments largely depend on the subjective visual evaluations of physicians and clinical staff,” which we revealed early on are quite error-prone. The authors went on to say, “Inaccurate evaluation can result in serious consequences such as improper dressing selection, overlooked non-healing wounds, and delayed specialist referrals.” 

AI, though, can help mitigate these issues. It facilitates the quick analysis of massive arrays of wound images while simultaneously working with algorithms and databases. As a result, AI can precisely identify and classify wound characteristics, thus reducing a clinician’s time spent on assessments and subjectivity. And these aren’t just assumptions. AI tools have been studied, revealing low error rates of 14%. Plus, it can be trained to perform better through continuous learning. 

Even when little human intervention is involved, and half of the images lack a reference object, research finds that deep learning tools are still effective at determining wound size. 

From Descriptive Analytics to Predictive Modeling 

In addition to providing details on what’s happening right now (e.g., wound measurements), AI can take it a step further. Practitioners can use AI to foresee future trends and outcomes, like which wounds might need advanced intervention. 

Predictive analytics can approximate healing times, and amputation risk, give insights on treatment, and more. This helps providers and clinics: 

• Boost patient outcomes
• Improve patient satisfaction
• Reduce the burden of documentation
• Decrease overhead expenses 
• Earn incentive bonuses  

Stay Ahead with Accurate Wound Measurement Practices

As this wound measurement guide reveals, there are many simple and low-cost measurement techniques available. Yet, due to a lack of standardization and potential subjectivity, many of these practices lead to inaccuracies and less-than-ideal care outcomes. 

Image-based AI tools with advanced predictive analytics capabilities can help fill the gaps present in traditional methods. They have the potential to maximize clinician efficiency while improving patients’ health. With current trends showing a strong shift toward value-based care, organizations should adopt options that allow them to deliver a high standard of care in a streamlined manner.