title: Sheep Hip Arthroplasty Model of Failed Implant Osseointegration.
abstract: Early secure stability of an implant is important for long-term survival. We examined whether micromotion of implants consistently would induce bone resorption and formation of a fibrous membrane and thereby prevent osseointegration. One micromotion implant was inserted into one of the medial femoral condyles in ten sheep. The micromotion device consists of an anchor bearing a PMMA implant and a PE plug. During each gait cycle the PE plug will make the PMMA implant axially piston 0.5 mm. After 12 weeks of observation the bone specimens were harvested and a post-mortem control implant was inserted into the contra-lateral medial femoral condyle. Histomorphometrical evaluation showed that the surface on the implant observed for 12 weeks was covered by fibrous tissue. The control implants were covered by lamellar bone. No difference was found with respect to the volume fraction of lamellar bone in a 1 mm zone around the implants. This study indicates that implant micromotion is sufficient to induce bone resorption and formation of a fibrous membrane.
authors.affiliation: Orthopaedic Research Laboratory, Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jakobsen
authors.affiliation: Aalborg University Hospital, Department of Orthopaedics, Aalborg, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Kold
authors.affiliation: Orthopaedic Research Laboratory, Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Jørgen
authors.initials: J
authors.lastname: Baas
authors.affiliation: Orthopaedic Research Laboratory, Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.affiliation: Orthopaedic Research Laboratory, Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Rahbek
keywords: Bone resorption; implant fixation; implant micromotion.