Abstract
Objective: Although hydroxyapatite (HA)-coated implants are widely used for cementless total hip arthroplasty, there is controversy about the use of HA coating on the acetabular component. We reviewed our cases and compared those in which HA-coated cups were used with those in which uncoated cups were used.
Methods: We retrospectively compared the radiographical results of cementless hemispherical acetabular components made of titanium (Ti) alloy with three types of surface finish: (1) uncoated (49 hips), (2) HA coated (58 hips), and (3) HA and tricalcium phosphate (TCP) coated (94 hips). Uncoated and HA-coated cups had the same rough surface (except for the HA coating) of arc-deposited commercially pure (CP) Ti. HATCP-coated cups had a CP Ti fiber-metal surface. Conventional or highly cross-linked polyethylene liners and CoCr heads were used. The stability of the cup, osteolysis, and bony apposition to the cup were evaluated by plain radiographs and computed tomographic images.
Results: After follow-up of 5-15 (mean, 8.4) years, all the cups were in situ except for two uncoated cups revised because of dislocation and osteolysis. Biological fixation was significantly different among the three groups (chi-squared test). Bony stable fixation was achieved in 100% of HA-coated and HATCP-coated cups, while 90% of uncoated cups were bony stable (including the two revised cups), but 10% were fibrous stable. Focal bone apposition at zone 3 (“acetabular spot welds”) was seen more frequently on HA- and HATCP-coated cups than on uncoated cups. Periacetabular osteolysis was detected around the coated cups as well as around uncoated cups, but was not detected in cases in which highly cross-linked polyethylene was used.
Conclusion: HA-coated and HATCP-coated cups showed similar excellent radiographical results. Sealing effects of HA coating against osteolysis were not apparent. Although both the coated and uncoated cups showed satisfactory durability, comparison between HA-coated and uncoated cups suggested that the HA coating for acetabular components had favorable effects on osseointegration, reducing the slight risk of fibrous fixation.
