BackgroundThe design of foot and ankle orthoses is currently limited by the methods used to fabricate the devices, particularly in terms of geometric freedom and potential to include innovative new features. Additive manufacturing (AM) technologies, where objects are constructed via a series of sub-millimetre layers of a substrate material, may present the opportunity to overcome these limitations and allow novel devices to be produced that are highly personalised for the individual, both in terms of fit and functionality.Two novel devices, a foot orthosis (FO) designed to include adjustable elements to relieve pressure at the metatarsal heads, and an ankle foot orthosis (AFO) designed to have adjustable stiffness levels in the sagittal plane, were developed and fabricated using AM. The devices were then tested on a healthy participant to determine if the intended biomechanical modes of action were achieved.ResultsThe adjustable, pressure relieving FO was found to be able to significantly reduce pressure under the targeted metatarsal heads. The AFO was shown to have distinct effects on ankle kinematics which could be varied by adjusting the stiffness level of the device.ConclusionsThe results presented here demonstrate the potential design freedom made available by AM, and suggest that it may allow novel personalised orthotic devices to be produced which are beyond the current state of the art.

Rheumatoid arthritis is an inflammatory joint disease that can lead to pain, stiffness, and deformity, often with marked involvement of the small joints of the foot and ankle. Orthotic devices are commonly prescribed for this condition to lessen symptoms and improve function and mobility, and customized devices are most effective. The work reported in this paper has examined the feasibility of using an additive manufacturing-based approach to manufacture customized orthoses. In order to test feasibility, orthoses have been manufactured using the additive manufacturing technology of selective laser sintering, and have been evaluated through a small-scale patient trial (n = 7). The trial indicated that these orthoses performed as well as the patients' current prescribed customized devices in terms of the observed gait and subjective evaluation of fit and comfort. It is concluded that the feasibility of the additive manufacturing approach has been demonstrated, and further development of a mass customization system to deliver orthoses, together with exploitation of the design freedom offered by the manufacturing method, will give the overall approach significant clinical potential.

Background: Recently, additive fabrication has been proposed as a feasible engineering method for manufacturing of customized ankle foot orthoses (AFOs). Consequently, studies on safety, comfort and effectiveness are now carried out to assess the performance of such devices. Objective: Evaluate the clinical performance of customized (selective laser sintering) SLS-AFOs on eight subjects with unilateral drop foot gait and compare to clinically accepted (polypropylene) PP-AFOs. Study Design: Active control trial. Methods: For each subject two customized AFOs were fabricated: one SLS-AFO manufactured following an additive fabrication framework and one thermoplastic PP-AFO manufactured according to the traditional handcraft method. Clinical performance of both AFOs was evaluated during gait analysis. Results: A significant beneficial effect of both custom-moulded PP-AFO and customized SLS-AFO in terms of spatial temporal gait parameters and ankle kinematic parameters compared to barefoot gait of adults with drop foot gait are observed. No statistically significant difference between the effect of PP-AFO and of SLS-AFO was found in terms of spatial temporal gait parameters and ankle kinematic parameters. Conclusion: AFOs manufactured through the SLS technique show performances that are at least equivalent to the handcrafted PP-AFOs commonly prescribed in current clinical practice. Clinical relevanceManufacturing personalized AFOs with selective laser sintering (SLS) in an automated production process results in decreased production time and guarantees the consistency of shape and functional characteristics over different production time points compared to the traditional manufacturing process. Moreover, it reduces the dependency of the appliance on the experience and craftsmanship of the orthopaedic technician.

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