Introduction: Mid-term follow-up has demonstrated good implant longevity for titanium fiber mesh and sintered bead designs, but few reports exist demonstrating the results of titanium plasma spray coated acetabular components in primary THR.
Methods: Between 1992 and 1995, a single surgeon performed 305 non-cemented primary THA’s in 260 patients. The selection criteria for non-cemented fixation were age younger than 65 and/or good bone quality. The hemispherical titanium plasma sprayed acetabular components were implanted with under reaming of 2 mm. Solid shells were used if a snug fit was attained with the trial. Screws were used to supplement fixation based on the surgeon’s judgment. The polyethylene liners were machined molded from ram extruded Hi-fax 1900H polyethylene resin gamma-sterilized in air or argon (inert) gas with elevated walls and locked into the shell via a Ring-Loc mechanism. These were mated with a 28mm cobalt-chrome femoral head and modular femoral component of metaphyseal-diaphyseal fit design with proximal titanium plasma spray porous coating. 15 patients have died, and 35 patients were lost to follow-up, leaving 225 hips in 210 patients that constitute the study cohort. The mean age was 55 years (range 24 – 60 years), and average.
Results: From this cohorts of patients, seven hips have been revised, two for infection, one for instability and four for osteolysis. The remaining patients had an average HSS score of 38 out of 40 at recent follow-up. Radiographically, the average cup inclination was 38.8 degrees. Eight hips had one zone interface lucencies, while three had two zone lucencies. There were no cases of continuous interface radiolucency or failure to achieve bone ingrowth. Nine hips demonstrated osteolysis, mostly in zones 2. The acetabular components in the cases with osteolysis were shells with unfilled screw holes in 3 and shells fixed with screws in 6. No osteolysis was detected in cases with solid hemispherical acetabular shells.
Discussion: Hemispherical titanium plasma sprayed ace-tabular components have achieved excellent durability at medium term follow-up, with a low incidence of fixation failure or osteolysis, and a low re-operation rate, even in a young, active group of patients. However, shells with screw holes appear to predispose to osteolytic lesions.
