title: Different patterns of bone fixation with hydroxyapatite and resorbable CaP coatings in the rabbit tibia at 6, 12, and 52 weeks.
abstract: Applying bioactive coatings on orthopedic implants can increase the fixation and long-term implant survival. In our study, we compared a resorbable electrochemically deposited calcium phosphate coating (Bonit®) to a thin (40 μm) plasma-sprayed hydroxyapatite (HA) coating, applied on grit-blasted screw-shaped Ti-6Al-4V implants in the cortical region of rabbit tibia, implanted for 6, 12, and 52 weeks. The removal torque results demonstrated stronger bone-to-implant fixation for the HA than Bonit-coated screws at 6 and 12 weeks. After 52 weeks, the fixation was in favor of the Bonit-coated screws, but the difference was statistically insignificant. Coat flaking and delamination of the HA with multinucleated giant cell activity and bone resorption observed histologically seemed to preclude any significant increase in fixation comparing the HA implants at 6 versus 12 weeks and 12 versus 52 weeks. The Bonit-coated implants exhibited increasing fixation from 6 to 12 weeks and from 12 to 52 weeks, and the coat was resorbed within 6 weeks, with minimal activity of multinucleated giant cells or bone resorption. A different fixation pattern was observed for the two coatings with a sharper but time limited increase in fixation for the HA-coated screws, and a slower but more steadily increasing fixation pattern for the Bonit-coated screws. The side effects were more serious for the HA coating and limiting the expected increase in fixation with time.
authors.affiliation: Orthopaedic Department, Oslo University Hospital, Rikshospitalet, Oslo, Norway. ole.reigstad@gmail.com
authors.forename: Ole
authors.initials: O
authors.lastname: Reigstad
authors.forename: Carina
authors.initials: C
authors.lastname: Johansson
authors.forename: Victoria
authors.initials: V
authors.lastname: Stenport
authors.forename: Ann
authors.initials: A
authors.lastname: Wennerberg
authors.forename: Astor
authors.initials: A
authors.lastname: Reigstad
authors.forename: Magne
authors.initials: M
authors.lastname: Røkkum
mesh_terms: D000497:Alloys; D000818:Animals; D001863:Bone Screws; D002130:Calcium Phosphates / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D055664:Electrochemical Techniques; D008422:Materials Testing; D019736:Prostheses and Implants; D011817:Rabbits; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000033:anatomy & histology*; D014025:Titanium / Q000737:chemistry
chemical_list: D000497:Alloys; C519914:BONITmatrix; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; C031462:titanium alloy (TiAl6V4); D012822:Silicon Dioxide; D017886:Durapatite; D014025:Titanium