Matton Connor, Ngan Calvin C, Andrysek Jan
Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, Toronto, Ontario, Canada.
PLoS One. 2025 Sep 10;20(9):e0331895. doi: 10.1371/journal.pone.0331895. eCollection 2025.
Achieving optimal alignment and fit is a key aspect of ankle-foot orthosis (AFO) design, as it directly influences the effectiveness of the device. While digital workflows offer the potential to integrate quantifiable alignment measures and corrections into AFO design, a major challenge remains in controlling lower-limb positioning and alignment during 3D scanning. This study aimed to evaluate pediatric AFO alignment and shape differences of directly scanned (live scan) vs casted lower limb models. Eighteen participants aged 4-16 years treated by 5 certified orthotists were recruited. Participants and casts were scanned. Sagittal plane ankle-foot alignment differences were analyzed between pairs of live scan and cast models. Using digital tools, the ankle-foot alignment of the live scans was then corrected, and the alignment differences were re-evaluated to assess the re-alignment methods and allow for further shape comparisons. After correction, modification maps were generated to assess the shape differences (surface deviations) between the live scans and cast models. Shape differences were also assessed with respect to participant characteristics. The results of this study demonstrated that AFO users can be scanned in a nearly corrected position (mean sagittal plane angle difference = 0.85°, SD = 4.44°), and that digital tools can be used to measure and adjust ankle-foot alignment with high accuracy (<1°error). The modification maps revealed that the live scans closely matched the cast models, with shape differences consistently observed in the foot and heel regions. Mean differences ranged -2.12-1.45 mm, positive differences (cast larger) ranged 1.14-2.71 mm, and negative differences (cast smaller) ranged 1.50-3.47 mm. Height, age, and foot length had moderate effects on shape differences (ρ = 0.5-0.75), while significant differences were observed between orthotists (∊2 = 0.32). These findings can drive future advancements in the digital design and fabrication of AFOs.
实现最佳的对线和贴合是踝足矫形器（AFO）设计的关键方面，因为它直接影响该器械的有效性。虽然数字工作流程有潜力将可量化的对线测量和矫正整合到AFO设计中，但在3D扫描过程中控制下肢的定位和对线仍然是一个重大挑战。本研究旨在评估直接扫描（实时扫描）与石膏灌注下肢模型的儿科AFO对线和形状差异。招募了由5名认证矫形师治疗的18名4至16岁的参与者。对参与者和石膏模型进行了扫描。分析了实时扫描模型与石膏模型对之间矢状面踝足对线差异。然后使用数字工具对实时扫描的踝足对线进行矫正，并重新评估对线差异，以评估重新对线方法并进行进一步的形状比较。矫正后，生成修改图以评估实时扫描模型与石膏模型之间的形状差异（表面偏差）。还根据参与者特征评估了形状差异。本研究结果表明，可以在几乎矫正的位置对AFO使用者进行扫描（矢状面平均角度差 = 0.85°，标准差 = 4.44°），并且数字工具可用于高精度测量和调整踝足对线（误差<1°）。修改图显示，实时扫描与石膏模型紧密匹配，在足部和足跟区域始终观察到形状差异。平均差异范围为 -2.12 - 1.45毫米，正差异（石膏模型较大）范围为1.14 - 2.71毫米，负差异（石膏模型较小）范围为1.50 - 3.47毫米。身高、年龄和足长对形状差异有中等影响（ρ = 0.5 - 0.75），而不同矫形师之间观察到显著差异（∊2 = 0.32）。这些发现可以推动AFO数字设计和制造的未来进展。
