There are several intrinsic and extrinsic factors that can affect the rate of wound closure but a simplistic model of healing assumes that each patient has a maximum achievable healing rate. This will depend on factors such as co-morbidities, age, nutritional status, concordance and the individual treatment plan agreed with the patient.

Figure 1 - Idealised/ optimal wound healing curve.

Because chronic wound are slow to heal, it is often difficult to detect whether healing is taking place. Deep wounds which heal by regranulation will decrese in volume until newly-deposited tissue fills the wound. Complete closure is then achieved by re-epithelialisation, when keratinocytes "roll" over the granulation bed to form a new epidermal layer.

It is challenging to quantify the change in volume of a deep wound without an accurate 3D measurement tool. Depth estimates using a probe are difficult to perform in a consistent, repeatable way and visual estimates are even less reliable. This limitation means that a "first line" treatment may be used for several weeks without the wound regranulating. This is represented in figure 2 by the initial blue shaded area of duration T. Throughout this period the patient may be hospitalised or receiving home visits with little or no progress in healing. Thus both time and money is wasted during the interval between initiation of treatment and the realisation that the patient is not progressing (and therefore is in need of a revised treatment plan).

Figure 2 - An example of a "real world" healing curve.

Accurate and repeatable wound measurement will minimise the time taken to determine if a wound is responding to treatment and if so, the patient should remain on the same treatment plan. Conversely, accurate volume measurement will also indicate if the wound is not responding to the current theraputic regime, prompting a reassessment of the patient and a review of the treatment plan.

Finally, comparing the rate of wound closure with a "standardised rate" and adjusting for patient-specific parameters will help to determine whether the rate of healing is in line with expectations. This provides valuable information which a multi-disciplinary clinical team casn use to ensure that they optimise patient outcomes.