title: Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications.
abstract: Aim of this study was to evaluate the response of bone to novel biodegradable polymeric composite implants in the femora of growing rats. Longitudinal observation of bone reaction at the implant site (BV/TV) as well as resorption of the implanted pins were monitored using in vivo micro-focus computed tomography (µCT). After 12, 24 and 36 weeks femora containing the implants were explanted, scanned with high resolution ex vivo µCT, and the surface roughness of the implants was measured to conclude on the ingrowth capability for bone tissue. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe changes on the surface of Polyhydroxybutyrate (PHB) during degradation and cell ingrowth. Four different composites with zirconium dioxide (ZrO2) and Herafill(®) were compared. After 36 weeks in vivo, none of the implants did show significant degradation. The PHB composite with ZrO2 and a high percentage (30%) of Herafill® as well as the Mg-alloy WZ21 showed the highest values of bone accumulation (increased BV/TV) around the implant. The lowest value was measured in PHB with 3% ZrO2 containing no Herafill®. Roughness measurements as well as EDX and SEM imaging could not reveal any changes on the PHB composites׳ surfaces. Biomechanical parameters, such as the adhesion strength between bone and implant were determined by measuring the shear strength as well as push-out energy of the bone-implant interface. The results showed that improvement of these mechanical properties of the studied PHBs P3Z, P3Z10H and P3Z30H is necessary in order to obtain appropriate load-bearing material. The moduli of elasticity, tensile strength and strain properties of the PHB composites are close to that of bone and thus promising. Compared to clinically used PLGA, PGA and PLA materials, their additional benefit is an unchanged local pH value during degradation, which makes them well tolerated by cells and immune system. They might be used successfully for personalized 3D printed implants or as coatings of rapidly dissolving implants.
authors: University of Natural Resources and Life Sciences, Institute of Physics and Materials Science, Peter-Jordan-Straße 82, 1190 Vienna, Austria.
authors: M
authors: M
authors: Meischel
authors: Medical University of Graz, Department of Orthopedic Surgery, Auenbruggerplatz 5, 8036 Graz, Austria.
authors: J
authors: J
authors: Eichler
authors: Medical University of Graz, Department of Orthopedic Surgery, Auenbruggerplatz 5, 8036 Graz, Austria.
authors: E
authors: E
authors: Martinelli
authors: University of Natural Resources and Life Sciences, Institute of Physics and Materials Science, Peter-Jordan-Straße 82, 1190 Vienna, Austria.
authors: U
authors: U
authors: Karr
authors: Medical University of Graz, Department of Orthopedic Surgery, Auenbruggerplatz 5, 8036 Graz, Austria.
authors: J
authors: J
authors: Weigel
authors: Medical University of Graz, Department of Orthopedic Surgery, Auenbruggerplatz 5, 8036 Graz, Austria.
authors: G
authors: G
authors: Schmöller
authors: Vienna Technical University, Faculty of Physics, Institute of Solid State Physics, Karlsplatz 13, 1040 Wien, Austria.
authors: E K
authors: EK
authors: Tschegg
authors: Medical University of Graz, Department of Orthopedic Surgery, Auenbruggerplatz 5, 8036 Graz, Austria.
authors: S
authors: S
authors: Fischerauer
authors: Medical University of Graz, Department of Orthopedic Surgery, Auenbruggerplatz 5, 8036 Graz, Austria.
authors: A M
authors: AM
authors: Weinberg
authors: University of Natural Resources and Life Sciences, Institute of Physics and Materials Science, Peter-Jordan-Straße 82, 1190 Vienna, Austria. Electronic address: stefanie.tschegg@boku.ac.at.
authors: S E
authors: SE
authors: Stanzl-Tschegg
mesh_terms: D000268:Adhesiveness; D000818:Animals; D000069343:Bone-Implant Interface; D004355:Drug Stability; D005269:Femur / Q000000981:diagnostic imaging / Q000378:metabolism; D006885:Hydroxybutyrates / Q000737:chemistry* / Q000378:metabolism*; D008297:Male; D008422:Materials Testing; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism*; D000091402:Prohibitins; D051381:Rats; D017207:Rats, Sprague-Dawley; D033081:Shear Strength; D016474:Weight-Bearing; D055114:X-Ray Microtomography; D000094122:Polyhydroxybutyrates
chemical_list: D006885:Hydroxybutyrates; D011091:Polyesters; D000091402:Prohibitins; C000717332:Phb protein, rat; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates
keywords: Bone-implant interface; Bone–cell ingrowth; In vivo degradation; Polymeric bone implants; Surface roughness; µCT