Increased risk of revision of acetabular cups coated with hydroxyapatite.
BACKGROUND
Hydroxyapatite (HA) is the main inorganic component of bone, and HA coating is widely used on acetabular cups in hip arthroplasty. It has been suggested that this surface finish improves cup survival.


METHODS
All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 with an uncemented acetabular implant that was available either with or without HA coating were identified. 8,043 total hip arthroplasties (THAs) with the most common cup types (Harris-Galante, Romanus, and Trilogy) were investigated. A Cox regression model including type of coating, age, sex, primary diagnosis, cup type, and type of stem fixation was used to calculate adjusted risk ratios (RRs) for the risk of revision.


RESULTS
HA coating was a risk factor for cup revision due to aseptic loosening (adjusted RR 1.7; 95% CI: 1.3-2). Age at primary arthroplasty of < 50 years, a diagnosis of pediatric hip disease, the use of a cemented stem, and the Romanus and Harris-Galante cup types were also associated with statistically significantly increased risk of cup revision due to aseptic loosening.


CONCLUSIONS
Our findings question the routine use of HA-coated cups in primary total hip arthroplasty. With some designs, this practice may even increase the risk of loosening-resulting in revision surgery.
Lazarinis
Stergios
S
Department of Orthopaedics, Institute of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden.
Kärrholm
Johan
J
Hailer
Nils P
NP
D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D020099:Coated Materials, Biocompatible; D017886:Durapatite; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D012307:Risk Factors; D013548:Sweden
D020099:Coated Materials, Biocompatible; D017886:Durapatite