Foot arch development of Chinese children and longitudinal evaluation of total contact foot orthosis for flexible flat foot for 2.5 years

Abstract

Flexible flat foot is a common lower extremity condition in children. However, there is still no universally accepted radiographic or clinical definition of flexible flat foot. Debates in literature on whether or not to provide orthotic treatment to children with flexible flat foot are due to the disagreement in defining flexible flat foot. Whilst various static footprint parameters have been commonly used to define flexible flat foot, recent literature emphasizes that static parameters have no predictive power of foot function. Instead, it is suggested that foot measurements should be analyzed during gait in order to understand the biomechanical behaviour of the foot. On the other hand, an effective orthotic treatment should be based on a series of a systematic protocol including reliable foot impression procedure, foot model rectification method, objective orthotic design, correct fitting, as well as regular inspection of outcome measures. However, these important procedures are rarely carried out systematically the literature. In light of the problems in the literature, flexible flat foot should be assessed using dynamic foot assessment. Longitudinal follow-up with systematic management should also be conducted to understand the course of the flexible flat foot in Chinese children. This thesis aimed to investigate these problems and was subdivided into two phases. Phase One of the study aimed to analyze the foot growth and gait patterns of Chinese children. The normative values of gait, anthropometric foot structures and general joint laxity data were investigated to understand the normal lower limb development in Chinese children. This project was also a continuation of the previous study to classify the feet with abnormally high midfoot loading during walking using a dynamic footprint parameter, Contact Force Ratio (CFR). CFR is a measure of midfoot to total loading of the contacted foot just before heel off during stance phase using a pressure sensing mat. Results showed that CFR generally decreased across age 6 to 11 in growing children. Children with CFR greater than age group mean plus one S.D. were defined as having abnormal flexible flat foot (AFFF). Furthermore, it was determined that children with AFFF exhibit significantly higher degree of joint laxity and higher rate of overweight or obesity. The normalized navicular height was also found to be lower in children with AFFF. The correlating factors of AFFF must be well identified in the management. Phase Two of this study was a longitudinal follow-up study of custom designed total contact foot orthotic treatment on Chinese children aged 6 to 9 having AFFF. With similar baseline characteristics between treatment group (With custom designed total contact foot orthotic intervention) and control group (Without any foot orthotic intervention), the effects of custom designed total contact foot orthotic treatment on children with AFFF were evaluated for 2.5 years. Static and dynamic foot measurements were taken at baseline, 0.5 year, 1 year, 1.5 years, 2 years and 2.5 years of the treatment. Outcome measures showed that the CFR decreased significantly after the treatment in age 6 to 8 but not in age 9 in treatment group. However, outcomes arising from the static footprint measures using Arch Index (AI) were not sensitive enough to evaluate the orthotic treatment results. This ascertained that the static and dynamic behaviours of the human foot are different and demonstrated the importance of assessing the human foot in the dynamic approach instead of static footprint approach. The biomechanical effects of the orthotic treatment were also investigated. Normalized midfoot and the medial forefoot loadings were significantly decreased after the orthotic treatment for 2.5 years. Long-term orthotic treatment in children with AFFF might maintain certain corrective effects to reduce abnormal midfoot loading during stance. The orthotic intervention could be prescribed for children with AFFF at age 6.