Assessing 3D printable density-graded lattice structures to minimize risk of tissue damage from compression-release stabilized sockets.

Abstract

Pressure, shear stress, and friction can contribute to soft tissue damage experienced by a residual limb. Current compression/release stabilized (CRS) socket designs may pose a risk to soft tissue from abrupt compression differences within the socket.Objectives:Density-graded lattice structures are investigated for their potential to mitigate risk of tissue damage by assessing their ability to produce more gradual transitions between high-compression and low-compression areas.Study Design:A full factorial experimental design was used to reveal the effects of changes among three variables: lattice geometry, density alteration, and displacement magnitude. A total of 144 experimental conditions were examined. Lattice samples representing areas of compression and release based on a novel cushioned transhumeral level CRS style socket design were 3D printed. Compression testing was performed on 2 types of lattice structures which incorporated 1 of 8 design elements to alter density and axial stiffness. The effect on stiffness of the sample as a function of lattice type and density alteration was recorded under 3 loading conditions. The offset diamond lattice type with blend radius density alterations produced the only samples meeting criteria set for compression areas of the socket. No samples satisfied criteria for release areas. Transitional density lattices that gradually tapered between the best performing compression and release values were successfully produced. Transitional density lattices offer promise for mitigation of soft tissue damage through minimization of compression differentials throughout the socket. Wider implications for this research include use in sockets for other levels of amputation and in orthotics. Future work will focus on lattice optimization to improve release behavior within a modified CRS socket.