Ankle–foot orthoses (AFOs) are devices prescribed to improve mobility in people with neuromuscular disorders. Traditionally, AFOs are manually fabricated by an orthotist based on a plaster impression of the lower leg which is modified to correct for impairments. This study aimed to digitally analyse this manual modification process, an important first step in understanding the craftsmanship of AFO fabrication to inform the digital workflows (i.e. 3D scanning and 3D printing), as viable alternatives for AFO fabrication. Pre- and post-modified lower limb plaster casts of 50 children aged 1–18 years from a single orthotist were 3D scanned and registered. The Euclidean distance between the pre- and post-modified plaster casts was calculated, and relationships with participant characteristics (age, height, AFO type, and diagnosis) were analysed. Modification maps demonstrated that participant-specific modifications were combined with universally applied modifications on the cast's anterior and plantar surfaces. Positive differences (additions) ranged 2.12–3.81 mm, negative differences (subtractions) ranged 0.76–3.60 mm, with mean differences ranging from 1.37 to 3.12 mm. Height had a medium effect on plaster additions (r_s = 0.35). We quantified the manual plaster modification process and demonstrated a reliable method to map and compare pre- and post-modified casts used to fabricate children's AFOs.

踝足矫形器 (AFO) 是用于改善神经肌肉疾病患者活动能力的设备。传统上，AFO 是由矫形师根据小腿的石膏印模手工制造的，该石膏印模经过修改以纠正损伤。本研究旨在以数字方式分析这一手动修改过程，这是了解 AFO 制造工艺的重要第一步，以告知数字工作流程（即 3D 扫描和 3D 打印），作为 AFO 制造的可行替代方案。对来自一位矫形师的 50 名 1-18 岁儿童的修改前和修改后的下肢石膏模型进行 3D 扫描和注册。计算了修改前后石膏模型之间的欧几里得距离，并分析了与参与者特征（年龄、身高、AFO 类型和诊断）的关系。修改图表明，参与者特定的修改与铸件前表面和足底表面的普遍应用修改相结合。正差（加法）范围为 2.12-3.81 毫米，负差（减法）范围为 0.76-3.60 毫米，平均差范围为 1.37 至 3.12 毫米。高度对石膏添加有中等影响（r_s  = 0.35)。我们量化了手动石膏修改过程，并展示了一种可靠的方法来绘制和比较用于制造儿童 AFO 的修改前后的模型。