Fig 1.
Scanning protocol for digital shape capture.
The scanning protocol showing the participant (on the height adjustable bed), the orthotist (holding the participant’s foot), and the trained expert performing the scan. The orthotist ensured the participant’s knees aligned with the bed’s end and adjusted their ankle-foot alignment by bending the knee and raising the foot. After adjusting and maintaining the participant’s foot position with their hands held distal to the metatarsal heads, the orthotist and the participant were instructed to remain still for the duration of the scan.
Fig 2.
Orienting the AFO models using an XYZ coordinate system. a) Anatomical landmarks were used to define the XYZ coordinate system (red axes).
The X-axis is defined by the base and head of the 1st metatarsal, while the Z-axis intersects through the fibular head and is orthogonal to the X-axis. The XZ-plane aligns with the apex of the calcaneus and the Y-axis is orthogonal to both the X- and Z-axes. b) The proximal trimline intersected the fibular head in the XY-plane. c) The distal trimline intersected the 1st metatarsal head in the YZ-plane. d) Point-cloud cross sections are used to create 2 vectors (yellow axes), which represent the plantar surface of the foot and the tibia.
Fig 3.
Canfit constrained rotate tool.
The Constrained Rotate tool in Canfit was used to adjust ankle-foot alignment. The rotational constraints were set through the apex of the calcaneus and along the X-axis to ensure that only the leg was being bent. The shape of the foot was preserved, and ankle-foot alignment was corrected by bending the leg and moving the model into dorsiflexion or plantarflexion.
Table 1.
Absolute alignment results and global volume differences for digital and traditional shape capture.
Fig 4.
Bland Altman plot comparing sagittal plane angle of live and cast models before correction.
Fig 5.
Bland Altman plot comparing sagittal plane angle of live and cast models after correction.
Fig 6.
Mean differences in CSA between live and cast models along the length of the limb.
Shaded bands represent one standard deviation. Positive values denote the mean increase in CSA in the cast model relative to the live model, while negative values indicate the mean reduction in CSA.
Fig 7.
Anterior and posterior view of the modification maps of four participants.
a) Participant categorized as “Others”, male, with bilateral condition, and prescribed a hinged AFO. b) Participant categorized as “UMN”, male, with bilateral condition, and prescribed a AGR AFO. c) Participant categorized as “LMN”, female, with unilateral condition, and prescribed a hinged AFO. d) Participant categorized as “UMN”, male, with unilateral condition, and prescribed a hinged AFO.Red indicates depressed areas, whereas blue indicates elevated areas of cast vs live.
Fig 8.
Modification map illustrating the three-point force system for correcting pronation of the foot.
Pressure is applied laterally at the neck of the talus, serving as the center force in the three-point force system. Medial pressure is applied at the lateral calcaneus and lateral fifth metatarsal. Black circles indicate areas that deviate from the three-point force system.