Arc-deposited hydroxyapatite-coated cups: results at four to seven years

A second-generation arc-deposited hydroxyapatite-coated acetabular component was developed after detailed analysis of a failed first-generation grit-blasted hydroxyapatite-coated cup. In our prospective multicenter study we aimed to compare clinical results and survivorship of the newly designed cup to the previous cup and to a similarly designed porous-coated cup during the same time period. The effect of bearing surface-alumina-on-alumina to polyethylene-on-metal-was analyzed. Consecutive patients were assigned randomly to one of three groups: arc-deposited hydroxyapatite-coated cup with alumina-on-alumina bearing surface; porous-coated cup with alumina-on-alumina bearing surface; or porous-coated cup with polyethylene-on-metal bearing surface. A fourth comparison group with a grit-blasted hydroxyapatite-coated cup and polyethylene-on-metal bearing surface was culled from a previous study. Acetabular mechanical failure rate is 0.0%, 0.0%, 1.9%, and 11.2% for the arc-deposited hydroxyapatite-coated, porous-coated with alumina bearing surface, porous-coated with polyethylene-on-metal bearing, and grit-blasted hydroxyapatite-coated cup, respectively, at 4- to 7-years' followup. There are no cases of acetabular osteolysis or femoral neck scalloping and no radiolucent lines in any zone with the arc-deposited hydroxyapatite-coated cup. The cups with the alumina-on-alumina bearing surface had less scalloping of the femoral neck than those with a polyethylene-on-metal bearing surface. Early results with this second-generation arc-deposited hydroxyapatite-coated cup are promising.

Therapeutic study, Level I (high-quality randomized trial with statistically significant difference or no statistically significant difference but narrow confidence intervals). See the Guidelines for Authors for a complete description of levels of evidence.