title: Biological assessment of the bone-screw interface after insertion of uncoated and hydroxyapatite-coated pedicular screws in the osteopenic sheep.
abstract: The sheep seems to be a promising model of osteoporosis and biomaterial osteointegration in osteopenic bone. The long-term ovariectomized sheep model was used for the biological investigation of bone healing around uncoated and hydroxyapatite (HA)-coated pedicle screws in osteopenic bone. Four sheep were ovariectomized and four sheep were sham-operated. Twenty-four months after surgery, the animals were implanted with uncoated and HA-coated stainless steel screws in the lumbar vertebral pedicles. Four months later, bone-to-implant contact, bone ingrowth, and bone hardness were measured around screws. Uncoated stainless steel presented significantly (p < 0.0005) lower bone-to-implant contact in healthy and osteopenic bone compared with HA-coated stainless steel. HA significantly improved bone ingrowth in healthy bone (p < 0.05) compared with uncoated stainless steel. Osteopenia significantly (p < 0.05) reduced the area of bone ingrowth around the screw threads for both types of implants. In the inner thread area, bone microhardness significantly increased (p < 0.05) in HA-coated surface versus uncoated for healthy and osteopenic bone. HA coating significantly enhances bone-to-implant contact also in osteopenic bone in comparison with uncoated stainless steel surfaces. Bone ingrowth and mineralization are ameliorated by the osteoconductive HA coating. However, osteopenia seems to greatly influence bone ingrowth processes around the implanted screws regardless of the characteristics of the material surface.
authors.affiliation: Experimental Surgery Department, Research Institute Codivilla-Putti, Rizzoli Orthopaedic Institute, via di Barbiano, 1/10, 40136 Bologna, Italy. milena.fini@ior.it
authors.forename: M
authors.initials: M
authors.lastname: Fini
authors.forename: G
authors.initials: G
authors.lastname: Giavaresi
authors.forename: T
authors.initials: T
authors.lastname: Greggi
authors.forename: L
authors.initials: L
authors.lastname: Martini
authors.forename: N Nicoli
authors.initials: NN
authors.lastname: Aldini
authors.forename: P
authors.initials: P
authors.lastname: Parisini
authors.forename: R
authors.initials: R
authors.lastname: Giardino
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001851:Bone Diseases, Metabolic / Q000601:surgery*; D001863:Bone Screws; D020099:Coated Materials, Biocompatible; D004195:Disease Models, Animal; D017886:Durapatite / Q000494:pharmacology*; D005260:Female; D006245:Hardness Tests; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008422:Materials Testing; D016348:Osseointegration / Q000187:drug effects*; D015663:Osteoporosis, Postmenopausal; D010052:Ovariectomy; D012756:Sheep; D013193:Stainless Steel; D014945:Wound Healing
chemical_list: D001672:Biocompatible Materials; D020099:Coated Materials, Biocompatible; D013193:Stainless Steel; D017886:Durapatite