Outcome of an Acetabular Design with Hydroxyapatite Coating on a Rough Substrate

Outcomes of hydroxyapatite-coated cups have not been as consistently successful as outcomes of hydroxyapatite-coated stems; therefore, we studied a newer generation acetabular design with a plasma-sprayed hydroxyapatite coating on an arc-deposited rough titanium substrate. Our objective was to determine whether clinical and radiographic outcomes would be better than reported for earlier-generation designs. Ninety consecutive hips in 85 patients implanted with this design were followed up prospectively for 2 to 5 years after surgery. Hip scores improved from a preoperative mean of 59 (± 12) to final followup mean of 91 (± 12). One hip was revised for recurrent dislocation. No hips were revised for aseptic loosening. No cup had complete continuous radiolucent lines. Incomplete lucent lines were noted on early postoperative radiographs. With followup, radiolucent line length decreased by a mean 32% and radiolucent line density increased by 9%. Mean polyethylene linear and volumetric head penetration rates were 0.17 (± 0.16) mm/year and 73 (± 70) mm³/year, respectively. Head penetration rates were higher in men. No other factor (age, body weight, cup abduction, or anteversion angle) correlated with head penetration rate. Our study presents encouraging short-term results. Improvement in radiolucent lines suggests a beneficial effect of hydroxyapatite coating on osseointegration of the cup.

Level of Evidence: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.