Biocompatibility studies of percutanous implants in animal models usually involve numerous lethal biopsies for
subsequent morphometric analysis of the implant-tissue interface. A common drawback of the study protocol is
the restriction of the analysis to one final time point. In this study optical coherence tomography (OCT) was used
to visualize and enable quantification of the local skin anatomy in the vicinity of a percutaneous implant in an
animal model using hairless mice. Non invasive in vivo optical biopsies were taken on predetermined time points
after implantation and ex vivo in situ at the day of noticeable inflammation. The custom made Fourier-domain
OCT system was programmed for imaging with different scanning schemes. A spoke-pattern of 72 cross-sectional
scans which was centred at the midpoint of the circular shaped implants was acquired and worked best for the
in-vivo situation. Motion-artefact-free three-dimensional tomograms were obtained from the implant site before
excision and preparation for histology. Morphometric parameters such as epithelial downgrowth, distance
to normal growth and tissue thickness were extracted from the images with a simple segmentation algorithm.
Qualitatively, the OCT B-Scans are in good agreement with histological sections. Therefore, OCT can provide
additional valuable information about the implant-tissue interface at freely selectable time points before the
lethal biopsy. Locally confined quantitative assessments of tissue-implant interaction for in vivo postoperative
monitoring can be carried out.
The tissue engineering focuses on synthesis or regeneration of tissues and organs. The hierarchical structure of nearly all
porous scaffolds on the macro, micro- and nanometer scales resembles that of engineering foams dedicated for technical
applications, but differ from the complex architecture of long bone. A major obstacle of scaffold architecture in tissue
regeneration is the limited cell infiltration as the result of the engineering approaches. The biological cells seeded on the
three-dimensional constructs are finally only located on the scaffold's periphery. This paper reports on the successful
realization of calcium phosphate scaffolds with an anatomical architecture similar to long bones. Two base materials,
namely nano-porous spray-dried hydroxyapatite hollow spheres and tri-calcium phosphate powder, were used to
manufacture cylindrically shaped, 3D-printed scaffolds with micro-passages and one central macro-canal following the
general architecture of long bones. The macro-canal is built for the surgical placement of nerves or larger blood vessels.
The micro-passages allow for cell migration and capillary formation through the entire scaffold. Finally, the nanoporosity
is essential for the molecule transport crucial for signaling, any cell nutrition and waste removal.
Biodegradable metal implants for musculoskeletal and intravascular applications made of magnesium alloys
have been shown to degrade in-vivo by corrosion. The in vivo corrosion of magnesium alloys has the potential to
provide a new mechanism which will allow metal implants to be applied in musculoskeletal surgery as
biodegradable implants. This would particularly be true if magnesium alloys with predictable in vivo corrosion
rates could be developed. Since the magnesium corrosion process depends on the corrosive environment, the
corrosion rates of magnesium alloys under standard in-vitro environmental conditions are not directly
comparable to results obtained from an animal model. Synchrotron-radiation based microtomography (SRμCT)
enabled us to investigate non-destructively the in vivo corrosion as well as the osteointegration at the
implant-bone interphase at a high spatial resolution. Corrosion morphology and its metallurgical quantification
of pit formation could be obtained. Since the alloying elements of magnesium alloys have significant importance
for the degradation process in biological environments the biocompatibility depending on their local
concentration and distribution has to be investigated. For this purpose we used element-specific SRμCT to show
the spatial distribution without destroying the bone-implant interphase. The SRμCT setup at HASYLAB at
DESY will be an excellent tool in the future to develop suitable magnesium alloys and magnesium implants for
special medical applications.
Material properties of bone are crucial for studies regarding the mechanical behavior of bone. The mechanical behavior depends on the macro- and micro-architecture as well as the organic and mineral content of bone. The marco-architecture of bone is normally analyzed by plane radiographs. The micro-architecture of the trabecular bone can be imaged by high resolution CT imaging techniques using conventional x-ray tubes. However, fine structures in bone architecture cannot be sufficiently analyzed by this technique due to its limited resolution. High resolution CT imaging technique using synchrotron radiation generates images with a high spatial resolution of bone structures on a micron scale. Additionally, this imaging technique provides superior determination of local differences in the bone mineral density. Two microtomography techniques, first: based on conventional x-ray tubes and second: based on synchrotron radiation were compared in this study to detect fine bone structures such as inner trabecular channels. In two red howler monkeys (Alouatta seniculus) femora channel structures were found inside the trabecular bone by both techniques. Only synchrotron-based microtomography was able to detect layers of lower mineral density in the channel walls. The found structures in trabecular bone are normally expected in the Haversian channel walls of the cortical bone. However, the origin of the trabecular channel structure is not fully understood. We found, that synchrotron-based microtomography is a very valuable technique in the research of fine bone structures. Further research should focus on the impact of these findings on the mechanical properties of trabecular bone.