Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications

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 compute...

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Bibliographic Details
Published in:Journal of the mechanical behavior of biomedical materials 2016-01, Vol.53, p.104-118
Main Authors: Meischel, M., Eichler, J., Martinelli, E., Karr, U., Weigel, J., Schmöller, G., Tschegg, E.K., Fischerauer, S., Weinberg, A.M., Stanzl-Tschegg, S.E.
Format: Article
Language:English
Subjects:
Adhesiveness
Animals
Bone-Implant Interface
Bone–cell ingrowth
Drug Stability
Femur - diagnostic imaging
Femur - metabolism
Hydroxybutyrates - chemistry
Hydroxybutyrates - metabolism
In vivo degradation
Male
Materials Testing
Polyesters - chemistry
Polyesters - metabolism
Polymeric bone implants
Rats
Rats, Sprague-Dawley
Shear Strength
Surface roughness
Weight-Bearing
X-Ray Microtomography
µCT
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Summary: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. •Tested PHBs for biodegradable bone implants do not degrade within 36 weeks in vivo.•No or almost no accumulation of bone tissue and bone–cell ingrowth could be detected.•Low adhesive strength of bone-implant interface and no change over time was found.•Increasing the implant-surface roughness is suggested to stimulate bone–cell adhesion.•Alternative applications of specified PHB composites are proposed.
ISSN:1751-6161
1878-0180
DOI:10.1016/j.jmbbm.2015.08.004