Factors Affecting Foot Loading and Ulcer Risk in Diabetes Patients

Sharma, Neeraj (2021) Factors Affecting Foot Loading and Ulcer Risk in Diabetes Patients. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Diabetes is a number of diseases related to insulin imbalance, leading to hyperglycaemia and resulting in a variety of long-term pathophysiology. Neuropathy, one such long-term complication of diabetes, leads to a seven-fold increased risk for diabetic foot ulceration (DFU), having major socio-economic implications and affecting quality of life. A DFU accounts for more than 80% of total lower limb amputations, while 85% of diabetes-related lower limb amputations are avoidable(1). Early identification of the high-risk foot and ulcer prevention through timely clinical interventions, are key to averting a DFU. This thesis aimed to investigate the effect of novel biomechanical and neuropathic factors underpinning DFU development. Specifically, the association between Achilles tendon mechanical properties, limited ankle-foot dorsiflexion and altered loading of the foot during gait were examined for their effects on plantar pressure development as a proxy for DFU risk. The thesis presents a series of cross-sectional studies conducted in people with diabetic peripheral neuropathy (DPN, n=13) and healthy controls (Ctrls, n=13). Comparison of 4 pressure variables against common clinical risk factors identified peak plantar pressure and pressure-time integral the most appropriate proxy variables for DFU-risk and significantly correlated with established diabetic neuropathy indicators of DFU risk. Investigation of Achilles tendon stiffness showed significantly higher stiffness in DPNs than Ctrls (DPN 80 Nmm-1 vs Ctrl 53Nmm-1). Tendon stiffness was correlated with forefoot peak plantar pressure (rho=0.387, p<0.001). This study suggests that a stiffer ankle joint complex may alter the loading of the foot and therefore the pressures experienced under the foot. Investigation of walking strategy revealed that when compared with controls, DPNs showed a 10% earlier heel-rise, 3.5 deg. reduced dorsiflexion (p<0.05), slower gait velocity and wider base (p<0.001). Tendon stiffness correlated with gait velocity (rho=-0.479, p<0.001), peak dynamic ankle dorsiflexion (rho=-0.427), vertical peak ground reaction force (rho=0.644, p<0.001) and peak plantar pressure at the 2nd toe, while walking. Thus, gait strategy and pressures changed in DPNs and significantly correlated with tendon stiffness. This thesis concluded that increased stiffness of the ankle-foot joint complex is a key factor underpinning alterations to walking strategy and resulting in elevated forefoot plantar pressures and therefore increased DFU risk. The proposed early DFU risk assessments tools can impact pathways of delivering foot care to patients with diabetes.