This investigation was carried out to evaluate the bone healing efficacy of b-TCP and PRP combination in dogs with long bone fracture repaired with threaded intramedullary pinning. The bone formation scores (BFS) in group II was found significantly higher as compared to group I at different time intervals (Table 1). Similarly, the bone union scores (BUS) were non significantly higher in group II as compared to group I (Table 2). Stage of union was achieved earlier in group II as compared to group I (Fig 1). The increase in the mean radiographic scores in group II due to application of osteoconductive material, b-TCP and osteoinductive material, PRP at the fracture site might have led to increase in the bone formation rate.
Goel et al., (2013) and
Preethi et al., (2021) also reported the osteoconductive abilities of b-TCP which was safe and effective therapeutic option for fracture healing in large osteo-periosteal defects. Addition of PRP to b-TCP enhance healing process, which is suggestive of beneficial effects of growth factors present in the PRP as reported based on effects of hydroxyapatite tricalcium phosphate (HA/b-TCP) on healing of bone defects in the skull of rabbits
(Szponder et al., 2018; El Backly et al., 2014) and by incorporating PRP into osteoconductive material as a source of growth factors, bone production was accelerated by the activation of stem cells and the cellularity within the defects was improved. In contrast to above findings, many authors reported no beneficial effect of PRP and b-TCP on fracture healing in dogs
(Rabillard et al., 2009; Ozdemir and Okte, 2012).
The mean weight bearing score while standing (Table 3) improved gradually over a period of time in both the groups ranging from 0.00 ± 0.00 on day 0 to 2.33 ± 0.33 on day 60th in group I (Fig 2) and 0.00±00 to 2.89 ± 0.12 in group II (Fig 3), respectively. The mean weight bearing scores were better in group II during the entire post-operative period. Moreover, all animals showing non-weight bearing lameness in both the groups on day of presentation. Animals tend to carry the damaged leg off the ground because of pain in the affected fracture area due to inflammation and damage to the surrounding muscles
(Gupta, 2015). Significant increase in the weight bearing scores in group II was observed on 15
th day as compared to group I. Moreover, all the animals were found touching either the toe or the paw on the ground in group II, whereas in group I, majority of the animals were carrying the limb off the ground. An improvement in the weight bearing score was observed in group I and most of the animals were found touching the toe or placing the paw on the ground on 30
th day. Majority of the animals started full weight bearing on the affected limb on 30th day in group II. Animals of both the groups showed full weight bearing on 60
th day postoperatively.
Similarly, the weight bearing scores while walking (Table 4) was non significantly higher in group II as compared to group I at different intervals. Similar findings were also observed by
Singh et al., (2020). The improvement in the weight bearing scores (while standing and walking) was due to early and optimum fracture healing in dogs of group II as supported by radiographic scores which can be related to local application of b-TCP and PRP at the fracture site. Similar results were observed by
Singh et al., (2020) in dogs treated with combination of b-TCP and PRP. This suggests the positive effects of PRP in bone union soft tissue healing surrounding the fracture site. Many authors reported the beneficial effects of PRP on healing of soft tissue trauma
(Boyan et al., 2007; Wang et al., 2013).
In group I, functional usage of the limb was excellent in one case, good in two, poor in two and fair in one. In group II, excellent in five cases, good in three and fair in one. This finding also coincides with the fact that animals of group II achieved early callus formation and early weight bearing, hence an early return of limb function with full range of motion. Similar findings were observed by
Singh et al., (2020).
β-TCP aid in bone healing by regulating osteogenic process like mesenchymal stem cell differentiation into osteoblasts, growth of new blood vessels, the release of angiogenic growth factors, and blood clot formation
(Lu et al., 2021). PRP could offer positive outcomes in bone grafting techniques, since it contains various growth factors
viz., platelet derived growth factor (PDGF), transforming growth factors (TGF- b1, TGF-b2), insulin like growth factor (IGF), epidermal growth factor (EGF) and epithelial cell growth factor (ECGF). These growth factors promote angiogenesis, stimulate the growth and chemotaxis of chondrocytes, osteoblasts, and mesenchymal cells
(Gracia et al., 2012). Osteoblast differentiation, proliferation and metabolic activity are intimately associated with platelet-derived growth factors (PDGF) and other proteins secreted by platelets, which activate intracellular signalling pathways for matrix formation and cellular differentiation. Platelet-rich plasma has a major impact on the early inflammatory phase of fracture healing, which includes the formation of a fracture hematoma and the proliferation of mesenchymal stem cells produced from the bone marrow
(Canbeyli et al., 2018).