Assessment of the Impact of Loading Pressure on Endothelial Function in Diabetic Foot

  • Rania Edris

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Background: Despite increased awareness and efforts to improve prevention, foot problems account for the most serious and costly complication of diabetes. High pressure and endothelial dysfunction are two major contributing elements in the development of diabetic foot ulceration. 

Aim of the study: To investigate foot pressures experienced on both dorsal and plantar surfaces of the foot, and the impact of pressure application on endothelial function of the superficial skin blood vessels on both aspects of the foot in subjects with Type 2 diabetes mellitus in comparison to a group of control without diabetes.

Methods: In-shoe pressure experienced on dorsal and plantar surfaces of the foot were assessed using Pedar insole system in subjects’ own shoes and orthopaedic shoes known to be prescribed for diabetic patients. In-shoe peak pressures (PP) were applied by a device designed to deliver a known pressure along with housing a laser Doppler flowmetery probe to assess blood flow changes. The effect of pressure on the skin blood flow response to iontophoresis of acetylcholine (ACh), an endothelium-dependent vasodilator and sodium nitroprusside (SNP), an endothelium-independent vasodilator, were assessed in a group of subjects with Type 2 diabetes and an age-matched control group of subjects with no diabetes.

Results: No significant differences were found between the two study groups in dorsal PP within the orthopaedic shoes (p=0.409) as well as in participants’ own shoes (p=0.389). However, both study groups had a significantly higher dorsal PP (p<0.001) in their own shoes when compared with the orthopaedic shoes. No significant differences in planter PP were detected between groups in participants’ own shoes (p=0.384), though, midfoot areas were significantly higher in diabetes groups and lateral areas under toes and metatarsal heads were significantly reduced. The orthopaedic shoes showed a significantly higher plantar PP (p=0.013) in the diabetes group compared to control. A significantly higher in-shoe plantar PP within participants’ own shoes than orthopaedic shoes (p<0.05) was noted in both study groups. However, this significant difference was apparent in one foot area in the diabetes group. No significant correlations were detected between PP and changes in blood flow in response to the iontophoresis of ACh or SNP on dorsal and plantar surfaces in both study groups. Both study groups have shown a significant reduction (p<0.001) in blood flow response to the iontophoresis of ACh and SNP under own shoes PP as well as orthopaedic shoes PP than resting /no pressure condition on the dorsal and plantar surfaces of the foot. A significantly higher change in response (p<0.05) was recorded in the control group than diabetes in blood flow changes in response to iontophoresis of ACh under no pressure. The control group showed a significantly higher change in response (p<0.001) under the orthopaedic shoes dorsal PP than own shoes with ACh and SNP while diabetes group only recorded a significant change in response with SNP. The diabetes group had a significantly higher blood flux values on the plantar surface in response to ACh iontophoresis in resting /no pressure, under orthopaedic PP and own shoes PPs. However, no significant differences from the control group were detected in changes in response from baseline flux with the iontophoresis of ACh or SNP on the plantar surface under any of the pressure conditions.

Conclusion: Although orthopaedic footwear had significantly reduced total in-shoe PP, pressure assessment is essential to adjust shoe design in-order to better distribute dorsal as well as plantar pressures and achieve effective offloading required for ulcers prevention. Diabetes group showed an increased blood flow values on the plantar surface, which could have been caused by an early sympathetic neuropathy. Additionally, diabetes group had an impaired endothelium-dependent response which may predispose to foot ulceration and the development of vascular complications in this group.
Date of Award2020
Original languageEnglish
SupervisorFaisel Khan (Supervisor) & Graham Arnold (Supervisor)

Keywords

  • Foot pressure
  • Diabetic Foot
  • Endothelial Dysfunction

Cite this

Assessment of the Impact of Loading Pressure on Endothelial Function in Diabetic Foot
Edris, R. (Author). 2020

Student thesis: Doctoral ThesisDoctor of Philosophy