Italian Researchers Use Field-Driven Lattice Design to Cut Prosthetic Socket Weight by 25%

From plaster model to digital workflow

A prosthetic socket is the critical interface between an amputee's residual limb and the rest of an artificial limb. Its inner section contacts the limb and distributes pressure, while the outer shell carries structural loads and houses electrodes, batteries, electronics and the wrist attachment. Researchers from four Italian universities have rebuilt that workflow around 3D scanning and generative design.

The process started with a volunteer recruited through Orthopedic Panini in Milan. An iPhone 15 Pro Max and Ortenshape captured the residual limb, the opposite limb and a plaster model. Scan data moved through Autodesk Meshmixer, Fusion and nTop. Two iterations corrected the liner's overall alignment, then two more refined its anterior surface — a reminder that human-in-the-loop fitting stayed necessary.

Turning stress into lattice geometry

Weight reduction came from a single-layer lattice applied to the patient-specific outer shell. Its square-and-diagonal unit cell gave an almost isotropic in-plane response suited to the curved geometry. Rather than model every strut, elastic-plastic homogenization represented the lattice as an equivalent continuous material. Ten strut diameters from 0.5 mm to 5 mm defined stiffness, shear response, Poisson's ratio and yield behaviour, with a 1.5 mm minimum imposed to limit local flexibility and manufacturing sensitivity.

Finite element analysis fixed the inner-liner interface and applied a distributed 100 N load at the wrist housing — simulating weightlifting with the elbow flexed at 90 degrees. An initial uniform-lattice simulation generated the stress field. MATLAB split it into 16 intervals, each linked to a material-property set and corresponding strut diameter. High-stress regions got thicker members; lower-stress areas used thinner ones. nTop then converted the diameter field into the final graded lattice and blended it with the socket's solid sections.

Lightweighting changes the structural trade-off

The optimized socket was manufactured on an HP Jet Fusion 4200 using HP 3D High Reusability PA12. Its modelled weight was 373 g, versus 434 g for a uniform mean-property lattice and 500 g for the bulk model — a 25.4% reduction relative to the bulk version. The cost: maximum anterior deflection rose from 0.7 mm to 1.6 mm and the minimum predicted safety factor dropped from 6.7 to 4.2. CT inspection showed a modal strut diameter of about 1.4 mm in the printed part (1.5 mm in CAD), comfortably within the CT system's 127 µm voxel uncertainty and confirming the graded lattice is manufacturable with MJF.

Why field-driven design matters

The study, led by Borracci et al., shows that lattice geometry can be treated as a load-bearing design variable rather than a blanket weight-saving trick. By grading strut thickness to the actual stress field, engineers keep material only where it earns its place — a principle already resonating in bone scaffolds and other medical prints where architecture is adapted to mechanical and biological need.

Source: 3D Printing Industry, reporting on research by Borracci et al. (four Italian universities), manufactured on HP Multi Jet Fusion 4200.