Hydroxyapatite coating versus cemented fixation of the tibial component intotal knee arthroplasty - Prospective randomized comparison of hydroxyapatite-coated and cemented tibial components with 5-year follow-up using radiostereometry

Fifty-three consecutive patients (57 knees; mean age, 69 years) entered a p rospective randomized study to compare the fixation of hydroxyapatite (HA)- coated (29 knees) with cemented (28 knees) tibial components in the Tricon II total knee arthroplasty. The quality of the fixation during 5 years post operatively was evaluated with radiostereometric analysis (RSA). Three HA-c oated implants were revised: 2 owing to infection, and 1 owing to early del amination of the coating and clinical loosening. Eight patients (9 knees) d ied, 1 patient sustained a stroke, and 1 patient refused investigations aft er 1 year. In the 40 patients (19 HA-coated, 21 cemented) remaining at 5 ye ars, the magnitude of the micromotion between the HA-coated and cemented gr oups did not differ. The HA-coated implants displayed most of the migration within the initial 3 months then stabilized, whereas the cemented implants showed an initially lower, but over time continuously increasing migration . Between 1 and 2 years, 4 of 24 HA-coated and 10 of 23 cemented implants m igrated >0.2 mm and were categorized unstable, which has been shown to have a prognostic value as regards future aseptic loosening. Progressive radiol ucent lines developed in 2 cemented knees, which both were categorized unst able. If HA-coated implants can sustain the forces that threaten the fixati on in the early period after implantation, a strong and enduring fixation m ay be obtained.