Acetabular components and additive manufacturing: does it all add up?

Advances in 3D printing, known as additive manufacturing (AM), have allowed for the production of highly porous trabecular metals (TMs) that aim to 'mimic' human bone and facilitate bony ingrowth. AM is increasingly being used to produce acetabular implants which incorporate TMs to varying degrees, to try and create a well-fixed acetabular component and, as a result, reduce the rate of aseptic loosening. This review details the history of uncemented acetabular implants and the developmental milestones towards these novel 3D-printed components, highlighting key steps in the complex design rationale of these intricate designs and why they are thought to be beneficial. To date, there has been no clear consensus on the optimum structural design or even manufacturing technique for acetabular implants, despite the plethora of AM implants already widely available on the market. Further evaluation of the manufacturing literature, as summarized, displays a paucity of preclinical studies or appropriate biological models that account for the dynamic stresses seen across a newly implanted acetabular component and the implications for a clinical setting. This review evaluates the differences seen across previous studies and implants which are currently commercially available. We highlight the need for further comparisons and evaluation of this rapidly evolving area of orthopaedics, together with suggestions to advance the field.