Individual Manufacturing from digital PRocesses : human - orthopaedic device INTerface – IMPRINT

Prostheses and orthoses enable people with physical impairments or functional limitations to live healthy, productive, independent, dignified lives and to participate in education, the labour market and social life. The current design and manufacture of Prosthetic and Orthotic device interfaces is dominated by hand-forming of thermoplastic materials on the plaster obtained via subtraction manufacturing techniques to allow for adaptation of the geometry to every user. This manual and iterative process is necessary to target optimal load transfer and ensure a good socket fit. At the same time, the process is highly dependent on the skill and experience of the prosthetist, as well as patient feedback with no quantitative prediction of fit prior to the manufacture of the socket. The current approach also hinders the automatization of the manufacturing chain and the use of mechanically based model for the optimization of shape and material properties.

Additive Manufacturing processes are now mature enough to be used to create Orthopaedic/medical devices which are functional and in their end-use state. However, challenges remain to integrate it in a fully digitalized procedure that can take into account personalized and user-oriented design. Biomechanical modelling has been identified as a potential tool to assist the prosthetist in their design process, by providing a prediction of fit prior to manufacture. Integrating such modeling in the manufacturing process would therefore be a major innovation. However, model validation is difficult due to the large inter- and intra-individual loading and anatomic variability including accurate description of the material properties, geometrical data, loading characteristics, and boundary and interface interaction conditions.

The IMPRINT project will be a timely contribution to the scientific and technological breakthroughs required for disrupting the Orthotics and Prosthetics market with digital processes and AM. To achieve this ambitious goal, IMPRINT will pursue four research objectives: 1/ Develop and evaluate an efficient modelling-simulation framework combining Gait Analysis, MusculoSKeletal simulations and Finite Element Analysis to investigate stump-socket interaction and quantify the impact of rectifications on biomechanical metrics used as surrogates for the goodness-of-fit of the prosthetic socket 2/ Collect experimental data on the inter- and intra-individual variability including accurate description of the material properties, geometrical data, loading characteristics, and boundary and interface interaction conditions 3/ Perform a mixed experimental-numerical parametric analysis to determine what model input parameters account for variability in the model output (interface pressure) 4/ Develop and integrate a 100% digitalized and waste-free manufacturing of all the orthoses and prostheses manufactured by PROTEOR. This includes all tasks required for an effective implementation of digital manufacturing cycle within 3D printing clusters and the development of a computer framework allowing to assist the prosthetist/orthotist in their design process, by providing a prediction of fit prior to manufacture.

Beyond the very positive ecological impact, this will also have a social and economic impact: improving the comfort and function of the prosthetic limb interface are substantial to improve quality of life of the Orthopaedic device user. This will pave the way for human-centered and flexible Digital Processes to meet the demand for innovative, personalized and optimized products in waste-free processes. From a more general scope, the underlying challenge addressed by the IMPRINT project extends to all the man-machine mechanical interfaces.