Background: The design freedom allowed by three-dimensional (3D) printing enables the production of acetabular\noff-the-shelf cups with complex porous structures. The only studies on these designs are limited to clinical outcomes.\nOur aim was to analyse and compare the designs of different 3D printed cups from multiple manufacturers (Delta TT,\nTrident II Tritanium and Mpact 3D Metal).\nMethods: We analysed the outer surface of the cups using scanning electron microscopy (SEM) and assessed clinically\nrelevant morphometric features of the lattice structures using micro-computed tomography (micro-CT). Dimensions\nrelated to the cup wall (solid, lattice and overall thickness) were also measured. Roundness and roughness of the internal\ncup surface were analysed with coordinate measuring machine (CMM) and optical profilometry.\nResults: SEM showed partially molten titanium beads on all cups, significantly smaller on Trident II (27 microm vs approximately70 microm,\np < 0.0001). We found a spread of pore sizes, with median values of 0.521, 0.841 and 1.004mm for Trident II, Delta TT\nand Mpact, respectively. Trident II was also significantly less porous (63%, p < 0.0001) than the others (Delta TT 72.3%,\nMpact 76.4%), and showed the thinnest lattice region of the cup wall (1.038 mm, p < 0.0001), while Mpact exhibited the\nthicker solid region (4.880 mm, p < 0.0044). Similar roundness and roughness of the internal cup surfaces were found.\nConclusion: This was the first study to compare the designs of different 3D printed cups. A variability in the morphology\nof the outer surface of the cups and lattice structures was found. The existence of titanium beads on 3D printed parts is a\nknown by-product of the manufacturing process; however, their prevalence on acetabular cups used in patients is an\ninteresting finding, since these beads may potentially be released in the body.
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