*4.2.1 Polymers*

Poly-L-lactic acid (PLLA) and poly-lactic-co-glycolic acid (PLGA) are the most commonly used polymers considered for their use as osteosynthesis and bone grafts [68]. Disadvantages of polymers include poor mechanical properties (low strength and stiffness, high brittleness) and osteoconductivity. Degradation behavior depends on monomers and can be very slow thereby increasing the risk of adverse effects such as sclerotic areas in bone and fibrous encapsulation [69].

Alternatively, polyhydroxybutyrate (PHB) can serve as a polymeric implant material, which is produced by microorganisms, especially bacteria. However, PHB can induce toxicological effects. However, these effects have been reduced dramatically, raising the potential for its application in clinics. Nevertheless, functional properties (i.e., osteoinductivity or osteoconductivity) of polymeric implant material have not been discovered yet.

### *4.2.2 Ceramics*

Ceramics are synthetic bone replacement materials with good biocompatibility and osteoconductivity, thereby showing good osseointegrative and nonimmunogenic effects. Composed of hydroxyapatite (HA), or alpha (α)- and beta (β)-tricalcium phosphates (TCP), ceramics exhibit poor mechanical properties including low yield strength and high brittleness, which make them unattractive for their application in load-bearing regions.

### *4.2.3 Bioresorbable metals*

In comparison to polymers and ceramics, iron (Fe), magnesium (Mg), and zinc (Zn) are more stable, tensile, and load-bearing, respectively. To process Fe-based alloys, the low melting point of Fe constitutes an interesting property. However, Hofstetter et al. demonstrated that limited access to oxygen was associated with slow degradation rates [70]. Metal implants based on Zn display several disadvantages including low rigidity and deformability, as well as corrosion inhibition. Therefore, Zn is likely more suited as an alloying element in combination with other materials. Finally, Mg-based alloys exhibit several advantages including good biocompatibility, resorbability, and favorable biomechanical properties. Moreover, some studies have demonstrated Mg's associated functional properties, especially its ability to support bone fracture healing [33]. For example, recent studies using

**35**

**Author details**

knee, femur, and tibia).

**5. Conclusion**

Austria

and Annelie-Martina Weinberg\*

provided the original work is properly cited.

Nicole Gabriele Sommer, David Hahn, Begüm Okutan, Romy Marek

\*Address all correspondence to: annelie-martina.weinberg@medunigraz.at

Department of Orthopedics and Traumatology, Medical University of Graz, Graz,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Animal Models in Orthopedic Research: The Proper Animal Model to Answer Fundamental…*

26 Mg isotope pins in a rat model demonstrated high Mg content in the boneimplant interface [71]. Good bone in-growth and a tight interface between bone and implant were observed. Additionally, drilled hole bone fractures showed full recovery after complete degradation of Mg implants. The serum concentration of Mg indicated a high tolerance of increased Mg levels which was controlled by urine excretion. Bone formation has been observed after implantation of XHP-Mg-0.45Zn-0.45Ca implants in young, growing small and large animal models [61].

Here, we summarized fundamental differences in small and large animal models concerning bone quality, composition as well as their individual advantages and disadvantages. Focusing on two major complications in orthopedics and traumatology, we wanted to underline the merits of an animal model by supporting with scientific results obtained from our intensive literature recherché. Implant research is a hot topic in orthopedics and trauma surgery. Based on our expertise, we wanted to give insights into implant technology, materials, and designs. Currently, permanent implants are the state-of-the-art material used to stabilize bone fractures in orthopedics and trauma surgery. However, to develop the ideal implant for a certain bone condition (e.g., osteoporosis and osteoarthritis), the underlying disease and the detrimental outcome on bone (e.g., bone mass, fracture risk, and bone density) have to be taken into account when choosing the implant material (e.g., Ti-, Mg-, Fe-based implants), design (e.g., pin, screw, plate, and scaffold), material properties (e.g., tensile strength, non- or bio-resorbable), and implantation site (e.g.,

Hence, it is of utmost importance to choose the most appropriate animal model

according to the research question and warranted primary outcome measures.

*DOI: http://dx.doi.org/10.5772/intechopen.89137*

*Animal Models in Orthopedic Research: The Proper Animal Model to Answer Fundamental… DOI: http://dx.doi.org/10.5772/intechopen.89137*

26 Mg isotope pins in a rat model demonstrated high Mg content in the boneimplant interface [71]. Good bone in-growth and a tight interface between bone and implant were observed. Additionally, drilled hole bone fractures showed full recovery after complete degradation of Mg implants. The serum concentration of Mg indicated a high tolerance of increased Mg levels which was controlled by urine excretion. Bone formation has been observed after implantation of XHP-Mg-0.45Zn-0.45Ca implants in young, growing small and large animal models [61].
