Comparison of the Mechanical and Osseointegrative Performance of Porous Tantalum and Titanium for Acetabular Implantation in Total Hip Arthroplasty: A Literature Review

Introduction: Stability of the acetabular component is a critical factor in the success of primary and revision total hip arthroplasty (THA) procedures. As such, the identification of implant surface characteristics that maximize stability of the acetabular cup is an important research objective. While titanium has historically been the most commonly used implant material, the proportion of THA procedures utilizing porous tantalum (PTa) implants has increased in recent years. The objective of this review is to examine the comparative mechanical and osseointegrative performance of PTa and porous titanium (PTi) and interpret these results in the context of primary and secondary stability of acetabular implants in THA, as characterized by strength of initial mechanical attachment and successful interlocking at the bone-implant interface, respectively. Methods: A literature search using a predetermined protocol and inclusion criteria yielded 7 articles presenting results of comparative testing of mechanical performance or osseointegration of PTa and PTi in the context of THA. Results: Neither PTa nor PTi presented consistently superior results in mechanical tests designed to correlate to primary stability at the metallo-biological surface nor in measures of osseointegration intended to represent secondary stability in THA. Discussion: In comparing PTa and PTi, it appears that the characteristics of the implant coating's pores may have a more significant impact on factors affecting the stability of an acetabular cup implant than the metal selected. However, determining the ideal pore morphology for this application is complex; pore characteristics that would suggest mechanical compatibility may conflict with those that would encourage more effective osseointegration. Conclusion: When extrapolated to be indicators of hypothetical clinical success, the results of this review are consistent with those of recently released macro-analyses of clinical outcomes: PTa and PTi acetabular cups, as they are currently manufactured, produce clinically equivalent outcomes. In the development and comparison of coating options, pore morphology and its complex effects on stability must be adequately accounted for; only then can we reach a faithful conclusion regarding the ideal porous adhesion surface for acetabular implant in THA.