Evaluation of the Bone Healing Process Utilizing Platelet-Rich Plasma Activated by Thrombin and Calcium Chloride: A Histologic Study in Rabbit Calvaria
To evaluate the bone healing of defects filled with particulate bone graft in combination with platelet-rich plasma (PRP), added with a mixture of calcium chloride and thrombin or just calcium chloride. Two 5-mm bone defects were created in the calvaria of 24 rabbits. Each defect was filled with particulate bone graft and PRP. In one defect the PRP was activated by a mixture of calcium chloride and thrombin; in the other, PRP was activated by calcium chloride only. The animals were euthanized 1, 2, 4, and 8 weeks after the surgeries, and the calvaria was submitted to histologic processing for histomorphometric analysis. The qualitative analysis has shown that both defects presented the same histologic characteristics so that a better organized, more mature, and well-vascularized bone tissue was noticed in the eighth week. A good bone repair was achieved using either the mixture of calcium chloride and thrombin or the calcium chloride alone as a restarting agent of the coagulation process.
Figure 1. Platelet-rich plasma (PRP) and topical bovine thrombin (TBT) – 1 week: newly formed bone matrix with an interlaced aspect, presence of connective tissue and newly formed bone matrix among the fragments of bone graft. Mallory Trichrome, ×22. Figure 2. PRP without TBT – 1 week: traces of blood clot in resolution process and several blood vessels. Bone graft fragments involved by newly formed bone tissue. Mallory Trichrome ×43. Figure 3. PRP without TBT – 2 weeks: thin bone trabeculae with several osteocytes included into the newly formed bone matrix and osteoblasts revesting the matrix surface. Hematoxylin and eosin ×43. Figure 4. PRP and TBT – 2 weeks: vascularized graft fragment with areas of apposition of newly formed bone tissue in its margins. Hematoxylin and eosin, ×43.
Figure 5. 4 weeks: bone neoformation filled the entire lesion with new bone tissue. Mallory Trichrome ×43. Figure 6. Platelet-rich plasma (PRP) without topical bovine thrombin (TBT) – 4 weeks: bone graft fragments incorporated by the newly formed bone tissue with empty lacunae and blood vessels. Hematoxylin and eosin ×43. Figure 7. PRP and TBT – 8 weeks: defect completely filled by bone tissue with regions presenting bone remodeling. Mallory Trichrome ×17. Figure 8. PRP without TBT – 8 weeks: bone tissue less cellularized and the thicker trabeculae delimiting smaller medullar cavities. Hematoxylin and eosin ×17.
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