Evaluation of a novel nanocrystalline hydroxyapatite paste Ostim in comparison to Alpha-BSM - more bone ingrowth inside the implanted material with Ostim compared to Alpha BSM

Abstract

Background: The purpose of this study was to evaluate the performance a newly developed nanocrystalline hydroxyapatite, OSTIM following functional implantation in femoral sites in thirty-eight sheep for 1, 2 or 3 months. Ostim 35 was compared to an established calcium phosphate, Alpha BSM.

Methods: Biomechanical testing, micro-CT analysis, histological and histomorphological analyses were conducted to compare the treatments including evaluation of bone regeneration level, material degradation, implant biomechanical characteristics.

Results: The micro-computed tomography (microCT) analysis and macroscopic observations showed that Ostim seemed to diffuse easily particularly when the defects were created in a cancellous bone area. Alpha BSM remained in the defect.The performance of Ostim was good in terms of mechanical properties that were similar to Alpha BSM and the histological analysis showed that the bone regeneration was better with Ostim than with Alpha BSM. The histomorphometric analysis confirmed the qualitative analysis and showed more bone ingrowth inside the implanted material with Ostim when compared to Alpha BSM at all time points.

Conclusions: The successful bone healing with osseous consolidation verifies the importance of the nanocrystalline hydroxyapatite in the treatment of metaphyseal osseous volume defects in the metaphyseal spongiosa.

Figure 1

Sample dimensions. The test specimens were prepared so that the implantation site was in the centre of the sample. The tissue samples were provided in physiological serum and the trials were performed within 48 h after removal.

Figure 2

Ostim^® agglomerates in transmission electron microscopy.

Figure 3

Defects centralized, confined (a) Alpha-BSM^® and (b) Ostim^®. The μCT images after three months of the bone replacement material implantation.

Figure 4

Alpha-BSM^® at 1 month. Masson's tricrome staining and 2× magnification of decalcified bone with calcium phosphate appearing as a still relatively compact matter. The osteoconduction process and newly formed bone were of limited grade and localized onto the interface (black arrows) between the edge of the original bone defect and the implant surface. (New bone = blue, Alpha-BSM = red)

Figure 5

Ostim^® at 1 month. Masson's tricrome staining and 2× magnification of decalcified bone 1 month after Ostim implantation. Particles of the HA-nanocrystalline paste are seen as round structures of different size in the bone marrow and within the bone trabecular tissue. The interface between implant material and host bone is indicated by the black arrows.

Figure 6

Alpha-BSM at 2 months. Masson's tricrome staining and 20× magnification of decalcified bone 2 months after Alpha-BSM^® implantation.

Figure 7

Ostim^® at 2 months. Modified paragon staining and 20× magnification of Ostim^® core surrounded by new bone formation.

Figure 8

Alpha-BSM^® at 3 months. Modified paragon staining and 10× magnification of Alpha BSM^® cement on the left upper quadrant of the image surrounded by newly formed bone.

Figure 9

Ostim^® at 3 months. Modified paragon staining and 5× magnification of non-decalcified bone 3 months after Ostim^® implantation. Ostim^® bone showed good osseointegration and bone remodeling.

Figure 10

Bone density inside the material in percent. Bone ingrowth was detected only 3 months postoperatively with alpha BSM a bone substitute.