Comparison of two pore sizes of LAE442 scaffolds and their effect on degradation and osseointegration behavior in the rabbit model

Abstract

The magnesium alloy LAE442 emerged as a possible bioresorbable bone substitute over a decade ago. In the present study, using the investment casting process, scaffolds of the Magnesium (Mg) alloy LAE442 with two different and defined pore sizes, which had on average a diameter of 400 μm (p400) and 500 μm (p500), were investigated to evaluate degradation and osseointegration in comparison to a ß‐TCP control group. Open‐pored scaffolds were implanted in both greater trochanter of rabbits. Ten scaffolds per time group (6, 12, 24, and 36 weeks) and type were analyzed by clinical, radiographic and μ‐CT examinations (2D and 3D). None of the scaffolds caused adverse reactions. LAE442 p400 and p500 developed moderate gas accumulation due to the Mg associated in vivo corrosion, which decreased from week 20 for both pore sizes. After 36 weeks, p400 and p500 showed volume decreases of 15.9 and 11.1%, respectively, with homogeneous degradation, whereas ß‐TCP lost 74.6% of its initial volume. Compared to p400, osseointegration for p500 was significantly better at week 2 postsurgery due to more frequent bone‐scaffold contacts, higher number of trabeculae and higher bone volume in the surrounding area. No further significant differences between the two pore sizes became apparent. However, p500 was close to the values of ß‐TCP in terms of bone volume and trabecular number in the scaffold environment, suggesting better osseointegration for the larger pore size.

Comparison of degradation behavior and osseointegration of 3D powder-printed calcium magnesium phosphate cement scaffolds with alkaline or acid post-treatment

“…For cancellous bone at the same location, the Th 142 was determined using µCT scans of both lateral femoral condyles of adult Zika rabbit cadavers ( n = 4) with intact femurs. Scaffold volume (SV) and scaffold surface area to volume ratio (SS/SV) were calculated following the studies of Kowalewicz et al (2021) , Augustin et al (2020) , and Kleer et al (2019) in a region of interest (ROI) in the scaffold center. This ROI included a cylinder with a diameter of 140 voxels (≙4.24 mm) and a height of 60 slices (≙1.82 mm) ( Figures 1C,D ).…”

“…This ROI included a cylinder with a diameter of 140 voxels (≙4.24 mm) and a height of 60 slices (≙1.82 mm) ( Figures 1C,D ). Bone volume (BV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) in the scaffold environment were calculated also based on the studies of Kowalewicz et al (2021) , Augustin et al (2020) and Kleer et al (2019) in a second hollow cylindrical ROI (inner ring: Ø = 144 voxel (≙4.36 mm), outer ring: Ø = 180 voxel (≙5.45 mm), height = 60 slices) ( Figure 1E ). To establish reference values for cancellous bone, the cancellous part of both femoral condyles of cadavers of adult Zika rabbits ( n = 4) with intact femora was examined.…”

Pore Size of 3D-Printed Polycaprolactone/Polyethylene Glycol/Hydroxyapatite Scaffolds Affects Bone Regeneration by Modulating Macrophage Polarization and the Foreign Body Response

“…Flatley et al reported that 500 μm pores were the optimum size for osteoconduction . Augustin et al implanted magnesium alloy LAE442 scaffolds with different pore sizes in rabbit femurs and ultimately observed significantly better osseointegration with a 500 μm pore size than with a 400 μm pore size . Considering these factors, we ultimately selected the pore sizes mentioned above.…”

“…25 Augustin et al implanted magnesium alloy LAE442 scaffolds with different pore sizes in rabbit femurs and ultimately observed significantly better osseointegration with a 500 μm pore size than with a 400 μm pore size. 26 Considering these factors, we ultimately selected the pore sizes mentioned above. The expression of the MyD88 protein, the key factor in the classic TLR4/MyD88/NF-kappa B pathway of macrophage polarization, 27 was quantitatively analyzed using immunohistochemical (IHC) staining to understand the potential mechanism by which the pore size of 3D-printed scaffolds affects macrophage polarization.…”

Effect of pore size on tissue ingrowth and osteoconductivity in biodegradable Mg alloy scaffolds

“…24,38 So far only solid LAE442 implants have been investigated [2][3][4]11,[18][19][20]39 and have achieved promising results with regard to peri-implant bone formation. 2,3,5,11,[18][19][20] LAE442 was used the first time in the form of open-pored scaffolds, with two firmly defined and always homogeneously reproducible pore size models in the study by Augustin et al 40 Associated investigations on the clinical tolerability as well as µCT measurements of the outer scaffold and bone environment provided promising results. Using high-resolution ex vivo µCT80 scan images, SEM/ EDX images, and histological tissue samples, the objective of the present study was to investigate which pore size model is more suitable as an osteoconductive and therefore potentially more suitable bone substitute for osteoneogenesis.…”