Early Experience with a New Porous Hemispheric Acetabular Component

Abstract

A third-generation cementless acetabular system has been designed, building on the successes of a second-generation system that featured good congruity between the liner and hemispheric shell, and proven porous plasma-sprayed coating on titanium alloy substrate, by designing a ringless barb and groove locking mechanism and optimizing range of motion. These design features are amenable to modern, highly crosslinked polyethylenes. A retrospective review was performed to assess early outcomes. A query of our practice registry revealed 534 patients (576 hips) who underwent cementless total hip arthroplasty performed by three surgeons with the G7™ Acetabular System (Biomet, Warsaw, Indiana) between April 2013 and March 2014. All liners were vitamin E infused, highly crosslinked polyethylene with a neutral face. Heads used were 463 BIOLOX® delta (81%; CeramTec AG, Plochingen, Germany) and 112 cobalt-chromium (19%), with diameters of 32 mm in 238 (41%), 36 mm in 331 (58%), and 40 mm in 6. Minimum one-year follow-up was available for 400 hips. Mean follow-up was 15 months (range 10-24, SD 3.0). Harris hip scores improved from 50.7 preoperatively to 86.5 most recently. UCLA activity scale improved from 4.5 preoperatively to 5.4 most recently. Two patients required cup revision secondary to failure of biological fixation at 8.4 and 15.1 months respectively. Radiographic findings in all cases were satisfactory position and alignment with no radiolucencies observed. In this group, with very early follow-up, good results with a low rate of acetabular revision and no dislocations were achieved using a new hemispheric porous shell with ringless barb and groove locking mechanism and geometry.