HYDROXYAPATITE COATING DOES NOT AFFECT SURVIVAL OF A TAPERED TITANIUM FEMORAL STEM: A SWEDISH NATIONAL HIP REGISTER STUDY ON 3,116 TOTAL HIP REPLACEMENTS

Abstract

Background: Hydroxyapatite (HA) coating is widely used for total hip arthroplasty as it has been suggested to improve implant ingrowth and long-term stability. However, the evidence behind the use of HA in femoral stems is ambiguous.

Methods: We investigated a non-cemented, tapered titanium femoral stem that was available either with or without HA coating. This stem had been used in 3,116 total hip arthroplasties (THAs) in 2,608 patients registered in the Swedish Hip Arthroplasty Register (1992–2007). Kaplan-Meier survival analysis and a Cox regression model including type of coating, age, sex, primary diagnosis, and the type of cup fixation were used to calculate adjusted risk ratios (RR) of the risk for revision for various reasons.

Results: 63.7% of the stems were coated with HA, 36.3% were uncoated. It was found that the investigated HA-coated stem had an excellent 10-year survivorship of 97.7% (95% CI 96.5–98.9), and that the stem without HA coating had a 10-year survivorship of 97.6% (95% CI 96.2–99.0) when revision due to any reason was defined as the endpoint. There was no significant difference between these two groups (p> 0.05, log rank Mantel-Cox). A Cox regression model showed that the presence of HA coating did not significantly influence the risk of stem revision due to any reason (RR 1.3; 95% CI 0.7–2.4), or due to aseptic loosening (RR 1.0; 95% CI 0.3–3.4). The risk for revision due to infection, dislocation, or fracture was also not affected by the presence of HA coating.

Interpretation: Our results show HA coating of this non-cemented tapered stem with excellent 10-year survivorship does not affect the risk for revision. The assumed beneficial effect of HA coating of femoral stems in total hip arthroplasty is thus questionable.