Abstract
BackgroundThree-dimensional (3D) printing of porous titanium implants is increasing in orthopaedics, promising enhanced bony fixation whilst maintaining design similarities with conventionally manufactured components. Our study is one of the first to non-destructively characterize 3D-printed implants, using conventionally manufactured components as a reference.MethodsWe analysed 16 acetabular cups retrieved from patients, divided into two groups: ‘3D-printed’ (n = 6) and ‘conventional’ (n = 10). Coordinate-measuring machine (CMM), electron microscopy (SEM) and microcomputed tomography (micro-CT) were used to investigate the roundness of the internal cup surface, the morphology of the backside surface and the morphometric features of the porous structures of the cups, respectively. The amount of bony attachment was also evaluated.ResultsCMM analysis showed a median roundness of 19.45 and 14.52 μm for 3D-printed and conventional cups, respectively (p = 0.1114). SEM images revealed partially molten particles on the struts of 3D-printed implants; these are a by-product of the manufacturing technique, unlike the beads shown by conventional cups. As expected, porosity, pore size, strut thickness and thickness of the porous structure were significantly higher for 3D-printed components (p = 0.0002), with median values of 72.3%, 915 μm, 498 μm and 1.287 mm (p = 0.0002). The median values of bony attachment were 84.9% and 69.3% for 3D-printed and conventional cups, respectively (p = 0.2635).Conclusion3D-printed implants are designed to be significantly more porous than some conventional components, as shown in this study, whilst still exhibiting the same shape and size. We found differences in the surface morphologies of the groups, related to the different manufacturing methods; a key finding was the presence of partially molten particles on the 3D-printed cups.
Highlights
Three-dimensional (3D) printing of porous titanium implants is increasing in orthopaedics, promising enhanced bony fixation whilst maintaining design similarities with conventionally manufactured components
Materials This study investigated 16 titanium-aluminium-vanadium (Ti6Al4V) acetabular cups received at our centre after being retrieved from patients
The “Results” section is presented according to the location investigated on the acetabular components, starting with the analysis performed on the internal cup surface and continuing with the investigation of the backside of 3D-printed and conventional cups
Summary
Three-dimensional (3D) printing of porous titanium implants is increasing in orthopaedics, promising enhanced bony fixation whilst maintaining design similarities with conventionally manufactured components. Additive manufacturing (AM) technologies, known as three-dimensional (3D) printing, are rapidly increasing in orthopaedics, in producing off-the-shelf cementless porous acetabular components for total hip arthroplasty (THA) [2,3,4,5]. Designed pore shapes can be produced using 3D-printing, unlike traditional technologies where there is a limited control over the porous structure layout [7].The clinical rationale behind the use of 3D-printing for customized (patientmatched) implants was to overcome the limitations of conventional custom components, which could not address complex cases where the bone stock was very limited. 3D-printing allows maximum control over the cup design, such as holes with reinforced edges and thinner cup walls for a given cup diameter, allowing surgeons to use larger femoral heads [8]
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