Sealing effect of hydroxyapatite coating on peri-implant migration of particles - An experimental study in dogs

We have studied the beneficial effects of a hydroxyapatite (HA) coating on the prevention of the migration of wear debris along the implant-bone inter face. We implanted a loaded HA-coated implant and a non-coated grit-blasted titanium alloy (Ti) implant in each distal femoral condyle of eight Labrad or dogs. The test implant was surrounded by a gap communicating with the jo int space and allowing access of joint fluid to the implant-bone interface, We injected polyethylene (PE) particles into the right knee three weeks af ter surgery and repeated this weekly for the following five weeks. The left knee received sham injections. The animals were killed eight weeks after s urgery. Specimens from the implant-bone interface were examined under plain and polarised light. Only a few particles were found around HA-coated implants, but around Ti im plants there was a large amount of particles. HA-coated implants had approx imately 35% bone ingrowth, whereas Ti implants had virtually no bone ingrow th and were surrounded by a fibrous membrane. Our findings suggest that HA coating of implants is able to inhibit peri-im plant migration of PE particles by creating a seal of tightly-bonded bone o n the surface of the implant.