An investigation into the variable biomechanical responses to antipronation foot orthoses

Sweeney, D 2016, An investigation into the variable biomechanical responses to antipronation foot orthoses , PhD thesis, University of Salford.

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Abstract

Antipronation foot orthosis are commonly used by health care professionals to treat a variety of lower limb conditions thought to be caused by excessive foot pronation. However, despite their widespread use, laboratory based research indicates that antipronation foot orthosis cause variable joint moment/motion biomechanical responses. If a specific biomechanical response is required to treat a specific clinical condition, it follows that practitioners cannot tailor foot orthosis confidently to alleviate symptoms thought to be associated with excessive pronation. A conceptual framework representing a biomechanical system of foot function was proposed to explain how external forces, foot structure, and neuromuscular factors cause these variable joint moment/motion responses to foot orthosis. Two studies (study 1 & study 2) sought to understand how external forces influenced joint moment/motion responses. Study 1 examined if systematic changes in external forces created by varying APFO geometry correlate to changes in joint moment/motion responses. To answer this research question a pilot study (n = 11) developed suitable increments in anti-pronation orthotic geometry that could systematically alter external forces under the plantar foot. The main study (n = 20) demonstrated that varying orthotic arch geometry and medial heel wedge geometry could systematically alter external forces (measured as peak pressure and centre of pressure) and joint moment/motion responses in foot structures. However, study 1 showed that changes in external forces created by varying APFO geometry are generally not strongly correlated (r < 0.6) to changes in joint moment/motion responses thus indicating that other factors (e.g. structural/neuromuscular) influence biomechanical responses to foot orthoses. On the basis that forces applied to the sole of the foot pass through plantar soft tissues prior to being applied to bones of a joint to affect moments and kinematics, study 2 characterised how soft tissue respond to change in external forces due to change in orthotic geometry. A pilot study (n = 10) developed a reliable method that could be used to quantify soft tissue thickness between the surface of an orthosis and bones overlying the medial arch. The results for the main study (n = 27) found that antipronation orthosis systematically compressed soft tissue structures under the plantar foot. The studies reported in this thesis show that antipronation orthosis can be tailored to systematically alter tissue compression, external forces and joint moment/motion responses. However, systematically altering external forces under the plantar foot with antipronation foot orthosis is not strongly correlated with changes in joint moment/motion responses. This suggests moment/motion responses are strongly influenced by structural features and/or neuromuscular action in combination with external forces. The work presented in this thesis offers a foundation for future studies seeking to understand how foot orthoses alters foot biomechanics.

Item Type: Thesis (PhD)
Schools: Schools > School of Health Sciences > Centre for Health Sciences Research
Funders: St Gabriel's Centre, Limerick, Ireland & Self funded
Depositing User: D Sweeney
Date Deposited: 20 Mar 2017 10:01
Last Modified: 20 Mar 2017 10:01
URI: http://usir.salford.ac.uk/id/eprint/40365

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