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. 2011 Jan 12:8:1.
doi: 10.1186/1743-0003-8-1.

Patient specific ankle-foot orthoses using rapid prototyping

Constantinos Mavroidis  1 , Richard G Ranky, Mark L Sivak, Benjamin L Patritti, Joseph DiPisa, Alyssa Caddle, Kara Gilhooly, Lauren Govoni, Seth Sivak, Michael Lancia, Robert Drillio, Paolo Bonato
Affiliations

Patient specific ankle-foot orthoses using rapid prototyping

Constantinos Mavroidis et al. J Neuroeng Rehabil. .

Abstract

Background: Prefabricated orthotic devices are currently designed to fit a range of patients and therefore they do not provide individualized comfort and function. Custom-fit orthoses are superior to prefabricated orthotic devices from both of the above-mentioned standpoints. However, creating a custom-fit orthosis is a laborious and time-intensive manual process performed by skilled orthotists. Besides, adjustments made to both prefabricated and custom-fit orthoses are carried out in a qualitative manner. So both comfort and function can potentially suffer considerably. A computerized technique for fabricating patient-specific orthotic devices has the potential to provide excellent comfort and allow for changes in the standard design to meet the specific needs of each patient.

Methods: In this paper, 3D laser scanning is combined with rapid prototyping to create patient-specific orthoses. A novel process was engineered to utilize patient-specific surface data of the patient anatomy as a digital input, manipulate the surface data to an optimal form using Computer Aided Design (CAD) software, and then download the digital output from the CAD software to a rapid prototyping machine for fabrication.

Results: Two AFOs were rapidly prototyped to demonstrate the proposed process. Gait analysis data of a subject wearing the AFOs indicated that the rapid prototyped AFOs performed comparably to the prefabricated polypropylene design.

Conclusions: The rapidly prototyped orthoses fabricated in this study provided good fit of the subject's anatomy compared to a prefabricated AFO while delivering comparable function (i.e. mechanical effect on the biomechanics of gait). The rapid fabrication capability is of interest because it has potential for decreasing fabrication time and cost especially when a replacement of the orthosis is required.

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Figures

Figure 1
Figure 1
Traditional fabrication process of an ankle foot orthosis for a patient.
Figure 2
Figure 2
Process used to fabricate the proof of concept AFOs.
Figure 3
Figure 3
Positioning of the foot during laser scanning. (A) Schematic of the setup and procedure used to scan the ankle of the subject. Note the relative positions of the cameras. (B) Lateral aspect of the foot and ankle as seen from the perspective of the right camera of the scanner.
Figure 4
Figure 4
Flow diagram of the post-scanning software procedures.
Figure 5
Figure 5
Position of the reflective markers used during the gait analyses.
Figure 6
Figure 6
Rigid RP AFO. (A) Example of the build platform. (B) Completed rigid RP AFO prototype.
Figure 7
Figure 7
Flexible RP AFO. A) The flexible RP AFO. (B) The positioning and fitting of the flexible RP AFO to the leg of the subject.
Figure 8
Figure 8
Ankle kinematics during the 4 testing conditions. (A) Average profile of ankle plantarflexion-dorsiflexion for five gait cycles of the No AFO condition (i.e. shoes only). The larger dashed vertical line represents the instance of toe-off and the lighter dashed vertical lines separate four different sub-phases of ankle function during the gait cycle (see text for details). (B) Average profiles of ankle plantarflexion-dorsiflexion for five gait cycles of the four testing conditions. Panels C - F show the mean (± SD) range of motion (RoM) in ankle plantarflexion-dorsiflexion for the four sub-phases illustrated in panel A for each of the four AFO conditions.
Figure 9
Figure 9
Ankle kinetics during the 4 testing conditions. (A) Average profiles of ankle flexor-extensor moments for five gait cycles of the four testing conditions. (B) Mean (± SD) peak ankle extensor and flexor moments for the four testing conditions.
Figure 10
Figure 10
Ankle power during the 4 testing conditions. (A) Average profiles of ankle powers for five gait cycles of the four testing conditions. (B) Mean (± SD) peak power absorption and power generation at the ankle for the four testing conditions.
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