Dynamic Loading of Tissues: Are Orthotics/Footwear Causing Perfusion Modulation?

Pain, Temperature & Perfusion Modulation: Are they related?

Southern Arizona Limb Salvage Alliance (SALSA) team is currently conducting several research studies spanning various lower extremity complications. Offloading modalities, orthotics or specialized footwear are invariably used for all our patients. The intervention mainly depends on the pathology. Patients with foot ulcers are prescribed an offloading modality until healing and then they are graduated to an orthotic or a diabetic shoe as needed. On the other hand, patients with plantar fasciitis are prescribed custom orthotics or sandals with pre-fabricated orthotic bed.

In a recent plantar fasciitis investigation comparing the efficacy of custom orthotics versus sandals with pre-fabricated orthotic beds, we observed a unique as well as consistent pattern of heel temperatures over 4 weeks, where the temperatures try to equilibrate over a period of time. The trend of temperature behaviour (increase or decrease) is dependent on the initial baseline temperature or inflammation. Interestingly, this behaviour correlates with the reduction of pain (as measured on Visual Analog Scale) over 4 weeks. This is an ongoing study and we will keep updating you on the results as they are available.

The key question is, “How do we describe this behavior?” Is it the perfusion modulation as a result of intervention and biomechanical alterations? It would stand to reason that, change in perfusion is a key permissive factor for superficial changes in skin temperature. What are the other factors that may influence this response and it’s correlation with level of pain? Well, it could be the ability of the orthotic/sandal to fine tune the biomechanics and subsequent perfusion modulation. Nevertheless, this is an interesting finding and may have direct implications on would healing and diabetic footwear.

Both vertical and shear stresses, induce hyperemia in tissue during loading (physical activity). Research has shown that dynamic/cyclic loading of the tissue alters the perfusion modulation in the tissue. This ability is compromised in the diabetic patients with loss of protective sensation under their feet. Therefore, the ability to measure the effect of prescribed orthotics clinically or at home may pave the way for pro-active care and better design of interventions. While there are indirect tools available currently like the handheld dermal thermometers, it may be worth to measure direct markers of perfusion modulation such as, tissue oxygenation in a serial fashion as an index for efficacy of footwear interventions for patients with diabetes. Perhaps, we can do both temperature and oxygenation through a single device!

Stay tuned for updates!

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