PROJECT SUMMARY Deformities of the hindfoot, including planovalgus, are common with cerebral palsy causing pain and limiting function. It is common when these patients are children to correct planovalgus deformity and improve alignment by surgically treating them with calcaneal osteotomies and subtalar fusions. However, long-term follow-up of adults living with cerebral palsy is limited. It is unknown what is driving the progression of deformity; it could be driven by the underlying bony morphology, altered neurologic control, or a combination of form and function that induces abnormal kinematics. Long-term assessments of foot reconstructions performed in childhood are important because continued growth and weight gain throughout puberty into adulthood can impede lasting improvements. Adults with cerebral palsy are underserved and there have been limited long-term studies investigating these childhood surgical interventions and their lasting effects as these patients transition to adulthood. Evaluating hindfoot kinematics during activities of daily living in adults with cerebral palsy is essential for understanding pathological foot conditions and the impact of past surgical interventions on long-term function. Biplane fluoroscopy provides a means to track in vivo motion of individual bones and measure joint kinematics. Yet, there lacks a robust standard for measuring and comparing kinematics across studies and conditions, especially in cases where deformity greatly affects bone morphology. Therefore, we propose two aims: 1) Standardize foot and ankle methods for data collection and kinematic model development using biplane fluoroscopy, and 2) Evaluate adults with cerebral palsy who have previously been surgically treated with a calcaneal osteotomy (Even’s lengthening) or subtalar fusion using the standardized methods in collaboration with Marquette University and Shriner’s Hospital for Children – Chicago to evaluate their long-term effectiveness. Our ultimate clinical research goal is to improve the orthopaedic management of foot deformities for individuals with cerebral palsy. Our mission is to conduct research to discover new knowledge that improves the quality of care and quality of life of adults with cerebral palsy. The long-term focus of this project will address outcomes as these patients grow into adulthood and achieve independence. This project clinically aims to identify long-term surgical correction strengths and deficiencies in adults living with cerebral palsy who underwent one of these two surgical treatments with the purpose to use this knowledge to guide future clinical decision-making. The secondary technical aim is to publish and provide standardized methods for evaluating tibiotalar and subtalar motion to facilitate additional future multi-center research studies to commonly evaluate surgical outcomes in the foot and ankle.