Porous hydroxyapatite ceramics and their ability to be fixed by commercially available screws.

We developed porous hydroxyapatite ceramics (HAP) which are screw fixable and evaluated the fixing abilities of commercially available screws using pull-out tests with the HAP implants. The fixing abilities were higher in the following order: Leibinger micro PLUS titanium screw > Osteomed M3 titanium screw > Leibinger standard mini screw > Martin-drill free screw. In preliminary examinations, the fixing ability of each of the screws differed according to the hole diameter and depth of insertion but if inserted under optimum conditions, all were deemed to have adequate fixing ability for clinical applications. Therefore, screw systems are superior for fixing HAP implants to surrounding bone than the use of thread or wire. Specifically, Leibinger's micro PLUS titanium screws system seems to be a good option currently. The fact that effective fixation was achieved should result in a further increase in the clinical use of synthetic porous HAP implants whose porosity and pore size are completely controlled for those purposes.