The functional analysis of shoe wear patterns : theory and application
Shoe wear patterns have potential value in clinical diagnosis and forensic identification, although they lack rigorous study. Podiatrists have claimed understanding of shoe wear patterns, associating foot pathologies with characteristic patterns and implying a "onecondition, one wear pattern" hypothesis. This project was commenced to understand and clarify this relationship. Round one of an initial Delphi exercise to seek agreements over such wear pattern associations however indicated that, many different patterns could be associated with single named foot pathologies with round three agreements appearing to relate to the most common pattern associations. Analysis of the patterns in the Delphi exercise produced an instrument to describe and compare shoe wear patterns using focal points - points from which areas of shoe wear would spread. A following survey questionnaire suggested that podiatrists were most familiar with wear patterns associated with four foot pathologies - pronation, hallux rigidus, pes cavus and rearfoot varus. Patterns associated with these pathologies were collected from U. K. podiatrists in a single round questionnaire. Inductive analysis of these patterns from a hermeneutic phenomenological perspective using the focal point concept suggested that if the pathological context is known, wear patterns could be classified on the basis of causative function. A theoretical model was proposed of factors important in wear pattern production, suggesting that primary walking intention (the intended walking function of the foot) was more influential than foot pathologies in wear pattern formation and that "external" factors could also influence shoe wear. Validation and grounding of the focal point concept and model of shoe wear influence was planned, involving paired podiatry observers, to determine whether focal points could clarify, differentiate and show similarities between shoe wear patterns in reality and whether the model of wear influence was justified. To reduce the potential for observer error, two prior exercises were undertaken. A Delphi exercise focused participants on the required task and produced statements for the recognition of variables, which may influence shoe wear patterns. Inter-observer reliability tests demonstrated that clinical observation agreement levels were acceptable for the validation. In the validation, three subjects exhibiting pathologies, including hallux rigidus, and their owned footwear (22 items) were studied. The presence, level and effect of variables potentially influencing the wear patterns present, were determined by paired observations of foot pathologies, shoe fit and function, video analysis of foot function and subject interview for the footwear history. The focal point concept showed similarities and differences between shoe wear patterns, although wear pattern clarity limitations occurred. Within the pathological context the patterns predicted the related functions. The model of wear influence was supported with external influences needing to be major to override primary walking intention and foot pathology effects. A method to describe and compare shoe wear patterns and a model to explain the link between function and wear, showing the relationship of factors important in wear pattern production have been produced. This model provides an alternative perspective on foot function to that of biomechanical theory and could represent the basis of a new taxonomy for podiatry. This greater understanding of shoe wear patterns should improve their potential value in forensic identification and in clinical diagnosis.