Ankle-foot orthotic (AFO) devices are designed to correct gait impairments for patients by stabilizing and securing the ankle-foot complex during gait. AFOs can be required for patients affected by a wide range of conditions including direct injury to the dorsiflexors, the common peroneal, the sciatic nerves, or the neural pathways that supply them. AFOs are also used to treat gait impairments resulting from conditions such as cerebral palsy, multiple sclerosis, or scoliosis, and are also common among subjects post-stroke who cannot properly dorsiflex their ankle or extend their toes. The patient, in rehabilitation therapy, uses such an orthotic device to ambulate daily, so it is essential that its shape maintains a high level of comfort while its material properties provide the necessary stiffness and support based on the patient's needs. However, AFOs are not created to fit the anatomy of a specific subject. Size ranges are built as an approximate fit for an anthropomorphic range of ankle-foot anatomy and, thus, are less likely to fit a particular subject comfortably. Standard models do not provide individualized comfort or support to the wearer. Considering the unique gait conditions and surface anatomy of each patient, an easy way to obtain custom made AFOs is required.
The current process to fit a custom AFO, which is depicted in FIGS. 1A-1F, is a laborious and time-intensive manual process performed by skilled orthotists. Once the orthotist has performed gait and muscle evaluation to determine the configuration and orientation of the subject's anatomy for corrective measures, the form of the device is captured by wrapping a sock around and then casting the leg (FIG. 1A). Markings are drawn onto the sock surface at key locations, which instruct technicians later on as to the corrective modifications that are necessary. After the cast has set (FIG. 1B), it is cut away along the anterior contour, in line with the tibia (FIG. 1C). The open edge of the cast is filled and plaster is poured into the leg cavity. During casting the original markings on the sock can slide along the surface up to ½″ away, introducing fabrication tolerances. This also requires the technician to have some fundamental anatomical and kinematic gait understanding to scrutinize the locations of the markings. Depending on the corrective measures desired, surface material is removed or added (FIGS. 1D, 1E) and thermoplastic is vacuum formed around the modified leg bust (FIG. 1F). Any further adjustments made to customize the standard orthotic device are carried out in a qualitative manner, so both comfort and function can remain sub-optimal.
An improved technique for fabricating a patient-specific orthotic device would provide the orthopedic specialist with the ability to obtain excellent comfort for a patient and also would allow for customized changes in the standard design to support the anatomy of the patient in the anatomical regions where such support would be most beneficial.