Manufacture of Passive Dynamic Ankle–Foot Orthoses Using Selective Laser Sintering

Abstract

Ankle-foot orthosis (AFO) designs vary in size, shape, and functional characteristics depending on the desired clinical application. Passive Dynamic (PD) Response ankle-foot orthoses (PD-AFOs) constitute a design that seeks to improve walking ability for persons with various neuromuscular disorders by passively (like a spring) providing variable levels of support during the stance phase of gait. Current PD-AFO manufacturing technology is either labor intensive or not well suited for the detailed refinement of PD-AFO bending stiffness characteristics. The primary objective of this study was to explore the feasibility of using a rapid freeform prototyping technique, selective laser sintering (SLS), as a PD-AFO manufacturing process. Feasibility was determined by replicating the shape and functional characteristics of a carbon fiber AFO (CF-AFO). The study showed that a SLS-based framework is ideally suited for this application. A second objective was to determine the optimal SLS material for PD-AFOs to store and release elastic energy; considering minimizing energy dissipation through internal friction is a desired material characteristic. This study compared the mechanical damping of the CF-AFO to PD-AFOs manufactured by SLS using three different materials. Mechanical damping evaluation ranked the materials as Rilsan D80 (best), followed by DuraForm PA and DuraForm GF. In addition, Rilsan D80 was the only SLS material able to withstand large deformations.

Gait assessment during the initial fitting of customized selective laser sintering ankle foot orthoses in subjects with drop foot

“…[17][18][19] The present study is the first one to (i) assess the effectiveness of SLS-AFO on drop foot gait and (ii) compare SLS-AFOs' clinical performance to clinical performance achieved using custom-moulded PP-AFOs.…”

“…In literature, there is evidence to support the use of additive manufacturing for producing orthotic or prosthetic devices. [13][14][15][16][17][18][19] However, issues related to material properties and manufacturing costs still need to be investigated before additive technologies could be considered ready for clinical use. Furthermore, it is not clear to the authors how much evidence is necessary before one can consider these manufacturing technologies 'ready for commercial' use.…”

How Does Ankle-foot Orthosis Stiffness Affect Gait in Patients With Lower Limb Salvage?

“…Clinical prescription of strut stiffness was based on the patient's available range of motion (ROM), activity level, types of activities performed, body mass, and active duty status (ie, indicating that they would carry heavy loads on a regular basis). All struts were initially designed in SolidWorks (Waltham, MA, USA) and constructed from Unfilled Nylon 11 powder (PA D80-ST; Advanced Laser Materials, Temple, TX, USA) using a selective laser sintering technique previously described [13,35]. Mechanical testing performed before biomechanical testing ensured the struts were within 5% of their intended stiffness.…”

X-ray computed tomography and additive manufacturing in medicine: a review

“…The authors concluded respectively that the materials used were highly useful in metallic appearance modelling (polyamide containing Al) and in direct tissue engineering applications (Ti6Al4V). Similarly, the paper by Faustini et al [50] in 2008 demonstrated the feasibility of XCT and AM in production of customised orthoses, although the authors chose in this instance to base a series of SLS orthoses on XCT data of an existing carbon fibre model instead of designing their product in direct reference to patient data. The authors compared AM orthoses of different materials to the traditionally manufactured carbon fibre reference, concluding that the method presented considerable promise for the field.…”