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Open Access Research article

Osseointegration and biocompatibility of different metal implants - a comparative experimental investigation in sheep

Michael Plecko18, Christine Sievert2, Daniel Andermatt3, Robert Frigg3, Peter Kronen24, Karina Klein2, Stefan Stübinger24, Katja Nuss2, Alexander Bürki5, Stephen Ferguson56, Ulrich Stoeckle7 and Brigitte von Rechenberg24*

Author Affiliations

1 Trauma Hospital, Goestingerstr.24, Graz, A - 8021, Austria

2 Musculoskeletal Research Unit (MSRU), Equine Hospital, Vetsuisse Faculty, University of Zurich, Winterthurerstr.260, Zurich, CH-8057, Switzerland

3 Synthes GmbH, Luzernerstr.19, Solothurn, CH-4500, Switzerland

4 Competence Center for Applied Biotechnology and Molecular Medicine (CABMM), Equine Hospital, Vetsuisse Faculty, University of Zurich, Winterthurerstr.260, Zurich, CH-8057, Switzerland

5 Institute for Surgical Technology and Biomechanics, University of Berne, Stauffacherstr.78, Berne, CH-3014, Switzerland

6 Institute for Biomechanics, ETH Zurich, Wolfgang-Pauli-Str.10, Zurich, CH-8093, Switzerland

7 Berufsgenossenschaftliche Unfallklinik Tübingen, Schnarrenbergstr.95, Tübingen, D-72076, Germany

8 University Hospital Zurich, Devision of Trauma Surgery, Rämistr.100, Zurich,CH-8091, Switzerland

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BMC Musculoskeletal Disorders 2012, 13:32  doi:10.1186/1471-2474-13-32

Published: 8 March 2012

Abstract

Background

In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep.

Methods

Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically.

Results

Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials.

Conclusion

This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior.