# The Thermo-Pressure Concept: A New Model in Diabetic Foot Risk Stratification
## 7 Discussion  
Plantar pressure has long been identified as a risk factor for ulceration in diabetes. However, the quest for identifying the true threshold value at which diabetic skin breaks down to form an ulcer has been ongoing for many years, and indeed the values presented in the scientific literature are far apart and range between 200 kPa and 1000 kPa. However, [PERSON] et al. reported that in patients living with DM with no complications, the duration of diabetes itself increases peak plantar pressure at the centre of the forefoot to over 300 kPa, possibly due to non-enzymatic glycosylation of the plantar fat pat, yet none of their subjects exhibited any ulceration [13]. This demonstrates that, on its own, peak plantar pressure may not be sensitive enough to predict ulceration in DM. Indeed, it has been shown to have a sensitivity of 60% as a risk factor.  
On the other hand, thermography is sensitive enough to detect temperature changes in the diabetes complications group, but in a static setting [22]. This study hypothesized that, if combined, temperature and pressure could be developed into a risk categorization model, termed a thermo-pressure model. This concept could be plausible when one considers that, before tissue breakdown, an inflammatory response is likely to occur at the site at risk of ulceration, possibly increasing the local temperature. On the other hand, if the pressure causes local ischaemia, the temperature is also likely to rise, as demonstrated by [PERSON] et al. Both these scenarios are known to commonly precede diabetic foot ulceration; hence, the timely detection of these two fused parameters could provide a pre-ulceration early warning mechanism.  
However, before this could be carried out, a study to determine whether there is a correlation between pressure and temperature needed to be performed. The authors believe that this is the first time that these two important parameters have been combined, and this study confirms that, in persons living with diabetes, there is a significant positive correlation between the two. Although in healthy individuals, including healthy DM persons, there is also a trend for the areas of pressure to become warmer, this correlation is less significant than in those patients with diabetic foot complications.  
This leads us to enquire whether, in the presence of pre-ulceration, this effect can be noted more than in subjects without pre-ulceration. This, unfortunately, was not possible to investigate within this study. Whilst the main strength of this study was the collection of thermal data following activity, as opposed to studies that have examined the thermal map of the diabetic foot at a purely sedentary level, there was an obvious limitation in that the participants needed to step down from the treadmill, undo their shoes and hosiery and get onto the couch for the thermal acquisition, meaning that these thermographic data were post-activity and, during the time elapsed, a slight drop in temperature could have occurred. This was minimalized by ensuring that thermal data capture was within 1 min of stopping the walking activity. In the future, it is envisaged to repeat this experiment using a custom-designed sensor that can measure both temperature and pressure simultaneously.