Efecto de los factores de crecimiento derivados de las plaquetas en la reparación de defecto óseo cortical

The Pure Platelet Rich Plasma (PRP-P) is a platelet concentrate readily available to release platelet growth factors and improve musculoskeletal tissue healing. This technology is not without controversy, as many authors obtain good results in the treatment of soft tissue disorders, however this beneficial effect on bone healing, repairing recalcitrant fractures or tissue regeneration is not so clear The great preparation methodology variability and different conditions of use, provide a high risk of making a wrong or improper use. The aim of this work is to study the effect of P-PRP on bone healing in an experimental animal model by creating a critical cortical bone defect and its relationship to the amount of growth factors released from platelets into the fracture focus in the presence and absence of cortical-cancellous allograft frozen in chip form. We conducted a standardized P-PRP with citrate dextrose without leukocytes and activated with thrombin and calcium. By double centrifugation, first at 500 g 10 min and then 1900 g 8 min. We have concentrated platelets in the P-PRP up to 7.1 times the baseline. An increase of growth factors release, PDGF (537.9 pg / ml) twice the basal and 8 times in the case of TGF β1 ( 7150 pg / ml) were obtained. The fracture model used was a critical defect in sheep ulnar in the proportion of more than 1.5 times the bone matrix core size of 20 mm in length in a period of 8 weeks duration. To improve the P-PRP osteogenic and osteoconductive capacity, we used 3.5 cc Cortical - Cancellous bone Allografts, not structural, in the form of chips pretreated with antibiotics. Monitoring bone consolidation was performed using image analysis (Image J), with histomorphometric parameters such as the volume of callus, trabecular thickness and the distance between edges of fracture. In addition, by plug-in Bone J, we have been able to relate the parameters of the trabecular geometry quality fracture callus from the study of the characteristics of the trabeculae, trabecular number, (connectivity, anisotropy, analized skeleton) and the relationship with the fractal dimension related to bone mineral density (BMD). The fracture callus bone mineral density were determined using a calibration adjustment with hydroxyapatite phamtoms of known concentration. The results obtained in our study, show that there is a positive correlation between growth factors released and the number of platelets within 3 hours after application. The addition of P-PRP to bone allograft, produces callus with smaller volume and lower trabecular thickness and it is a clear loss of mineralizing potential in the consolidation of callus, with a clear decrease in bone mineral density in all cases. Large differences in cellularity, mineralization and type of ossification were histologically assesed. These results show for the first time that the use of PRP affects the graft osteogenic and osteoinductive capacity which makes us suggest that the use of PRP appears that is not indicated for improving the cortical bone healing in critical defects.