Polyethylene wear in cases using femoral stems of similar geometry, but different metals, porous layer, and modularity.

In this report, 83 total hip arthroplasties in 75 patients with femoral stems of similar geometry but different metals, porous surfaces, and femoral head-neck design were compared at a mean follow-up of 66 months (range, 40-104 months). One type of acetabular component and polyethylene were implanted in all hips. The femoral stem was monoblock in 25 hips, and in 58 it had a modular head-neck piece; 70 stems had chrome-cobalt heads, and 13 heads were titanium. Equally satisfactory clinical results were obtained with either type of femoral implant (i.e., modular and monoblock). The calculated average annual linear polyethylene wear was significantly higher for the titanium stems with a plasma-spray porous surface and chrome-cobalt head on a Morse taper than the chrome-cobalt, beaded, monoblock stems (0.22 mm/year vs 0.07 mm/year, P < .0001). The prevalence of periprosthetic osteolysis was higher for these modular stems ( 15.7% vs 0%), but this difference was not statistically significant (P = .09). Gross corrosion was present on the taper surfaces of an autopsy-retrieved femoral implant with a modular cobalt-chrome head on a titanium stem. Particles of chromium 3-orthophosphate were present at the taper rim and in the periarticular tissues.