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.

Effect of Micrometer-Scale Roughness of the Surface of Ti6Al4V Pedicle Screws in Vitro and in Vivo

“…The sheep-spine model was chosen because of its similarities with a human spine in terms of anatomy, size, material characteristics, and biomechanical characteristics 23 . The study was approved by the Committee for the Supervision of Animal Experiments at the Hebrew University Hadassah (Jerusalem, Israel).…”

Collagen type I coating stimulates bone regeneration and osteointegration of titanium implants in the osteopenic rat

“…Nevertheless, in the present work, this interaction between implant site, osteoporotic condition and material was not evident in a statistically significant manner. Conversely, what Fini et al [30] first demonstrated concerning the osseointegration in osteopenic condition was confirmed: osteopenia mainly affects the BI parameter, which is the one mostly related to the healing ability of the host bone. On the other hand, BIC is less influenced by osteopenia, but rather by the surface modification of material and by the action that the latter is able to exert in the immediate proximity of the implant.…”

Osteointegration of bioactive glass‐coated and uncoated zirconia in osteopenic bone: An in vivo experimental study

“…On the contrary, there is general agreement that the AI improves after the implantation of bioactive ceramic-coated materials [i.e., hydroxyapatite (HA)] in osteopenic bone: the presence of the HA coating has been demonstrated to maintain high levels of AI even in osteopenic bone. 23,[42][43][44] However, in some osteopenic cases a significant decrease in the osteointe- gration rate has been observed in spite of the HA coating. 24,44 Regarding biological glasses, some have proved to osteointegrate only when implanted in healthy bone and not in osteopenic rat bone.…”