Applicability evaluation of direct metal tooling-based additive manufacturing for reducing ceramic liner fracture in total hip arthroplasty

Recently, the combination of a press-fit acetabular cup and ceramic articulation has been widely used for implanting cementless acetabular components and has been shown to provide good initial stability. However, this combination may lead to the failure of ceramic liners by their non-concentric seating due to acetabular cup deformation. To reduce the risk of this, we applied direct metal tooling (DMT)-based additive manufacturing (AM) with the hypothesis that DMT-based AM would minimize the deformation of the acetabular cup by increasing its strength, which would ultimately prevent the ceramic liner from fracturing. To confirm this, we performed post-fatigue tests simulating a press-fit situation for the acetabular cups subjected to DMT-based AM and compared them with the cups treated with titanium plasma spray (TPS). The post-fatigue tests were then performed under a maximum load of 14 kN for 20 x 10(7) cycles. The roundness and inner diameter of the cups and liners were measured in all testing phases. The results revealed no differences between the acetabular cups subjected to DMT-based AM and TPS. However, when comparing only the mean values directly, the results for the acetabular cup subjected to DMT-based AM indicated that it might have increased the strength of the acetabular cup, compared with those treated with TPS, thereby minimizing the possibility of fracture of the ceramic liner. In conclusion, DMT-based AM was shown to be at least equivalent to TPS, or could possibly supersede it. Additionally, via DMT-based AM, it is possible to control the porous structure freely, so this approach allows a greater range of applications and potential for further improvement than TPS.