Influence of external factors in the prescription of foot orthoses and their biomechanical consequences

• Main Author: Chevalier, Thierry Larose
• Published: Staffordshire University 2011
• Subjects: 617.58062
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551191

For many years, foot-care specialists have been employing foot orthoses in an attempt to treat various musculoskeletal disorders and pathologies. Anecdotal reports from patients and clinicians suggest foot orthoses achieve a high level of success in alleviating discomforts and symptoms. In contrast, the scientific community has yet to reach any consensus on their actual biomechanical effects. As there are a great many factors involved in any orthotic intervention, in addition to the orthoses themselves, which have the potential of affecting end results, it is difficult to study foot orthoses without taking these other factors into consideration. The objectives of this research were to study a number of external factors impacting foot orthoses and to assess their biomechanical effects. In this context, factors such as casting and practitioner variability, the type of device, i.e. custom-made orthoses vs. prefabricated orthoses, and the midsole composition were assessed. Using a single patient, clinically assessed by 11 different foot-care specialists, inter-practitioner variability was assessed. Through this study, it was found that a large amount of variation is introduced by practitioners themselves. Results suggest that patients will have different outcomes depending on which practitioner they consult. Consequently, great caution should be taken when transferring or generalising results on the biomechanical effects of custom-made foot orthoses. Generic effects of both custom-made and prefabricated foot orthoses were studied through ten patients clinically identified as overpronators. It was found that the custom-made foot orthoses in this study had only few systematic effects on patient during normal walking. The custom-made foot orthoses also did not have any significant effects on rearfoot eversion, forefoot abduction or internal tibial rotation. Most of their kinematic effects were limited to range-of-movement reductions. In addition, prefabricated foot orthoses were found to have similar effects to those of CFO. Thus, as the key difference between CFO and PFO is the optimisation process which CFO go through, it is assumed that such process is either irrelevant or unnecessary. Yet, caution should also be exercised in attempting to generalise the results as those only apply to the comparison of the specific devices used in this study. The results from the study on midsole stiffness suggest that no important interaction occurred between mid sole composition and the orthotic devices. Variations in midsole stiffness were mainly found to have effects on the antero-posterior shear force and time-domain variables. A negative relationship was also found between midsole composition and many range- of-movement variables. Nevertheless, it is hypothesised that a precisely chosen combination of midsole stiffness and FO could optimise clinical outcomes. Based on present findings, it is possible to conclude that many external factors will influence the effects FO have on patients, especially those factors present before the FO are dispensed to the patients. Nevertheless, orthotic interventions should take as many factors as possible into account, not only to obtain the best possible results but mainly to permit accurate, appropriately defined and predictable outcomes.