Reoccurrence of deformity can affect upwards of 64% of children with clubfoot. The ability to use foot function as a measure of reoccurrence has not been previously assessed. The purpose of this investigation was to utilize foot pressure analysis to predict the probability of reoccurrence in children with unilateral clubfoot. Retrospective foot pressure data revealed predictive algorithms detecting the probability of experiencing any type of reoccurrence (overall reoccurrence) and for experiencing a tibialis anterior tendon transfer (TATT). The equation for overall reoccurrence reported sensitivity and specificity of 0.82 and 0.81 and the equation for TATT reported values of 0.81 and 0.84. These algorithms were then applied prospectively to a cohort of children with unilateral clubfoot. Interim sensitivity and specificity results at a 1.5-year follow-up demonstrate that the equations for overall reoccurrence and TATT were highly specific but not sensitive (0.84, 0.73 specificity; 0.11, 0 sensitivity). This is an indication that these algorithms were more accurate when identifying the absence of reoccurrence. However, these results may change as the prospective subjects continue to age. Overall, the results of this investigation show that foot pressure analysis can predict the presence/absence of reoccurrence. The algorithms developed herein have the potential to improve long and short-term outcomes for children with clubfoot. Providing clinicians with the probability of reoccurrence will improve their ability to be proactive during the treatment decision making process.

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[pt] Valkó e Oligney propuseram um modelo que estima a evolução da fratura utilizando uma interpretação direta da curva de pressão de fundo medida durante uma operação de fracpack. Os únicos dados de entrada necessários para a aplicação do modelo são os registros geralmente disponíveis durante e após a operação. Considerando uma fratura de geometria radial e utilizando equações simples de fluxo e de geomecânica, o modelo obtém raios de empacotamento a partir da inclinação positiva da curva de pressão de fundo nos períodos de tip screenout. Nesta dissertação o modelo de Valkó e Oligney é aprimorado com a inclusão e o ajuste das equações de estado para o crescimento da fratura e para o processo de filtração, respectivamente. O modelo é também estendido para outras geometrias bidimensionais de fratura, PKN e KGD. A aplicação do modelo foi realizada utilizando os registros de pressão de oito operações de fracpack. Os resultados obtidos são a curva de propagação da fratura, o crescimento da abertura, a eficiência ao longo do tempo e a distribuição final do agente de sustentação na fratura. Para a validação desses resultados foram utilizados dois simuladores comerciais com modelos tridimensionais. Os estudos de caso indicaram que os ajustes realizados aproximaram os resultados do modelo aos obtidos nos simuladores comerciais. Além disso, a aplicação dos modelos desenvolvidos para cada geometria de fratura e a comparação com os resultados dos simuladores comerciais, permitiu confirmar a tendência esperada que, durante uma operação de fracpack, a geometria da fratura se aproxima da radial. / [en] Valkó and Oligney developed a model to estimate fracture evolution using a direct interpretation of the measured bottom hole pressure curve during a fracpack operation. The only input data needed to use the model are the usual records of the job, available during and after the operation. Considering radial fracture geometry and using simplified equations of flow and geomechanics, the model estimates a packing radius of the fracture using the slope of the increasing bottom hole pressure curve during the tip screenout period. In this work, Valkó and Oligney method is enhanced with the inclusion of state equations for the fracture growth and for the leakoff process in order to improve the model, but still maintaining minimum input data. The method is also extended to other two-dimensional fracture geometries, PKN and KGD. To apply the enhanced method, eight fracpack operation data were used. The results obtained are fracture propagation, width growth and fluid efficiency in time as well as the final proppant distribution in the fracture. To validate these results, this work used two commercial simulators with three-dimensional models. The case studies show that the modifications done to Valkó and Oligney method approximate the two-dimensional model results to the ones obtained using the commercial simulators with threedimensional models. Furthermore, the comparison between the application of the model for each fracture geometry and the commercial simulators results confirmed the expected tendency for the fracture geometry during a fracpack operation, which is a radial fracture.