Highly Porous Tantalum Acetabular Components Without Ancillary Screws Are Non-inferior at 7 Years When Compared With Titanium Components With Ancillary Screw Fixation: A Randomized Controlled Trial.

BACKGROUND

While porous tantalum components have shown to be advantageous in the revision setting, registry studies have identified tantalum components used in primary total hip arthroplasty (THA) to be associated with an increased risk of revision. The only study to examine the migration of tantalum acetabular components with radiostereometric analysis (RSA) beyond 2 years found continued migration. The aim of this 7-year follow-up RSA study was to determine if the mid-term migration of tantalum acetabular components without ancillary screw fixation is no greater than that of fiber metal titanium components with one ancillary screw fixation.

METHODS

We prospectively reviewed the mid-term implant stability of patients who underwent primary THA and were randomized intra-operatively to receive either the tantalum or titanium acetabular component. Of the initial 66 patients enrolled, 51 (77.3%) were available at 7-year follow-up; 2 tantalum components were revised due to recurrent dislocation and infection, respectively, and 2 titanium components underwent open reduction internal fixation to treat femoral periprosthetic fracture. Acetabular component migration relative to the surrounding acetabular bone was measured using RSA at 4-6 days post-operatively and at 6 weeks, 3 months, 1, 2, 3, 5, and 7 years following THA.

RESULTS

At 7 years, the mean proximal migration of tantalum components was 0.22 mm (95% confidence interval 0.08-0.35) and non-inferior to that of titanium components at 0.19 mm (95% confidence interval 0.07-0.32). In addition, the mean proximal migration of tantalum components was non-inferior to that of titanium at both 3 and 5 years. There were no significant differences noted between cohorts for any other axis of translation and rotation.

CONCLUSIONS

The continued mid-term stability of tantalum acetabular components without ancillary screw fixation is encouraging for long-term stability. The non-inferiority compared to titanium acetabular components with established excellent long-term survivorship provides reassurance to the operative surgeon using tantalum components in the primary setting.

LEVEL OF EVIDENCE

I.