Three-Year Results with a Ringless Third-Generation Porous Plasma Sprayed Acetabular Component in Primary Total Hip Arthroplasty.

Introduction: We previously reported promising early results in patients undergoing primary total hip arthroplasty (THA) with a third-generation cementless acetabular system that has a porous plasma-sprayed coating on a titanium alloy substrate shell, a ringless barb and groove locking mechanism, and a vitamin E-infused highly crosslinked polyethylene insert. The purpose of this study was to examine the outcomes and need for revision in a subset of patients previously reviewed who now have potential for three-year follow-up.

Patients And Methods: A query of our practice registry revealed 235 consented patients (241 hips) who underwent cementless primary THA performed by three surgeons with the G7® Acetabular System (Zimmer Biomet, Warsaw, Indiana) between April 2013 and September 2013. All liners were vitamin E-infused highly crosslinked polyethylene with a neutral face. Mean patient age was 65.8 years and mean BMI was 31.3 kg/m2. Heads used were 179 Biolox® delta (74%; CeramTec AG, Plochingen, Germany) and 62 cobalt-chromium (26%), with diameters of 32mm in 105 (41%) and 36mm in 136 (56%).

Results: A minimum three-year follow-up was available for 152 hips in 146 patients. Harris Hip Scores improved from 47.8 to 88.2, and UCLA activity scale from 3.9 to 5.4. One patient from this study period required cup revision secondary to failure of biological fixation at 15.1 months postoperative. There have been no dislocations or other revisions of the acetabular component. Kaplan-Meier survival with endpoint of acetabular revision was 99.5% (95% CI: 99.0% to 100%) at 3.4 years. Radiographic findings in all cases were satisfactory position and alignment with no radiolucencies observed.

Conclusion: In this study, with minimum three-year follow-up, good results with 99.5% survival were achieved using a third-generation cementless acetabular system with a ringless barb and groove locking mechanism.