Hydroxyapatite-coated implants provide better fixation in total knee arthroplasty. A meta-analysis of randomized controlled trials.

Background: The potential advantages of hydroxyapatite (HA)-coated cementless total knee arthroplasty (TKA) implants are bone stock preservation and biological fixation. Studies comparing the outcomes of HA-coated cementless, non HA-coated cementless (uncemented) and cemented TKA implants reported contradictory data. Our aim was to provide a comparison of the effects of HA coating of tibial stem on the stability and functionality of TKA implants.

Methods: A systematic literature search was performed using MEDLINE, Scopus, EMBASE and the CENTRAL databases up to May 31st, 2019. The primary outcome was Maximum Total Point Motion (MTPM) of the tibial stem. This parameter is determined by radiosterometric analysis and refers to the migration pattern of the prosthesis stems. The clinical outcomes of the implanted joints were evaluated by the Knee Society Knee Score (KSS) and the Knee Society Function Score (KFS). Weighted mean difference (WMD) with 95% confidence interval (CI) were calculated with the random-effects model.

Results: Altogether, 11 randomized controlled trials (RCTs) with 902 patients for primary TKA implants were included. There was a statistically significant difference in the MTPM values with the use of HA-coated and uncoated uncemented implants (WMD = +0.28, CI: +0.01 to +0.56, P<0.001). However, HA-coated stems showed significantly higher migration when compared with the cemented prostheses (WMD = -0.29, CI: -0.41 to -0.16, P<0.001). The KSS values of HA-coated implants were significantly higher than those for the uncemented implants; moreover, KSS and KFS outcome scores were statistically not different between the HA-coated and cemented prosthesis cases.

Conclusion: HA-coating yields better stability than other, uncemented prostheses. More importantly, the HA-coating is not outperformed by cemented prosthesis in providing good functional outcome.