*3.4. In Vivo Studies*

Figure 16 displays manufactured TCP Freeze Foams (porosities between 83–85%, with an average of 84%), TCP hybrid scaffold halves (porosities around 80%) and single ZrO2 Freeze Foams (porosities between 70–72%, with an average of 71%).

a. Clinical Examination

After implantation, all rats had a score of "0" overall. This score means, clinically, we had no signs that the surgery or the implants had negative influences on the rats. However, the evaluation of histological samples (fine needle aspiration and explanted implantation area) had not been commenced. However, for all of the presented in vivo results, the authors think that the gathered serum parameters are more important regarding our following in vivo assessments than histological analyses would be at this stage of the research. We base our argument on studies of Trevisani et al. [33]. The main findings of this study were that the agreement between chronic histological kidney damage (CKD) and CKD staging was poor. In fact, about 30–40% of patients with CKD stage 3 had mild or no lesions in the histological evaluation (Chronicity Score = 0–1), whereas 7 to 10% of cases with CKD stage 1 (eGFR > 90 mL/min/1.73 m2) had moderate or even severe histological lesions (Chronicity Score ≥ 3). Moreover, different patients with the same eGFR values may have had either severe (Chronicity Score ≥ 3) or no histological damage (Chronicity Score = 0) (eGFR = estimated glomerular filtration rate).

b. Serum Parameters

The serum parameters of day 0, 2, 7, and 14 were measured by the accredited laboratory of the Clinic for Ungulates of the Veterinary Faculty of the University of Leipzig. These results were evaluated in a box-plot diagram to adjust them according to the physiological parameters as described in Charles River 2008 [34] and Boehm et al. [35] (Figures 21 and 22). Regarding these analyses, a photometric measurement (extinction determination) was executed. The photometric method is applicable for multi-species analyses [36]. Since no references were sent by the clinic, we had to compare the determined values, especially the creatinine and urea values, with the literature references of Charles River [34] and Boehm et al. [35].

**Figure 16.** Comparison of the different manufactured scaffolds: left—TCP freeze foams, middle—TCP hybrid scaffold halves and right—ZrO2 Freeze Foams.
