While prosthetics are typically designed using a casting process, computer-aided design methods and 3D printing could change that.  A recent study in the American Journal of Physical Medicine & Rehabilitation has compared the two, with interesting results.

Traditionally, prosthetic fabrication has involved casting the impaired limb by hand, then producing a mold from which a socket can be designed. This can be a particularly laborious and time-consuming process, but has been a mainstay in socket manufacturing for many years. However, computer-aided design and computer-aided manufacturing (CAD/CAM) methods have recently been gaining increased attention. A new study suggests that these techniques could help improve patients’ rehabilitation after amputation.

In a recent study, 72 patients, ages 16-70, with a transtibial amputation were trialed with either a prosthetic socket made using CAD/CAM technology (Tracer CAD) or traditional carving technology, with 36 in each group. After rehabilitation, the groups’ pain scores, walking distance, duration of use, and pain-free walking time were compared, as well as other quality of life indicators. The CAD/CAM group adapted significantly quicker to their prosthetics, walked farther, had less reported pain with ambulation, and mostly had better measures in the Trinity Amputation and Prosthesis Experiences Scale. Patients were not blinded to the intervention, but these findings pointed to sockets manufactured through the newer, CAD/CAM method as potentially providing better quality of life for transtibial amputees.

Such methods typically involve getting a digital image of the patient’s extremity using a scanner, then turning the image into a 3D model with CAD software. From here, the model can be adjusted as needed and then sent to the manufacturer for production (sometimes even onsite). 3D printing is another such method that utilizes CAD/CAM technology, by taking a 3D model and “printing” it through multiple extruded layers of material (often plastic or metal, with material composition still a challenge in weight-bearing prosthetics). Proponents of the CAD/CAM methods point to faster socket production, and the potential for better accuracy, from 3D mapping of the patient’s anatomy over traditional methods.

While these findings offer some support for utilizing CAD/CAM methods in prosthetic fabrication, they don’t directly explore 3D printing. One of the key challenges in 3d printing for lower limbs is finding the appropriate materials to print with that will withstand the demands of ambulation. So far, this remains an area in need of further research. 3D printing of upper limb devices has been explored to a greater extent, with the NIH hosting a 3D Print Exchange website for sharing and downloading prosthetic files. At the moment, they all appear to be for the upper limb, although as this technology evolves we will likely see lower limb models appear as well.