Use of biomaterials for the treatment of bone defect

Bone is a complex tissue and most of the skeletal injuries are due to blunt trauma including long bone fracture. Fracture can cause serious complications both preoperatively and postoperatively. The method and timing of fracture fixation and its management is still debatable. Traditionally bone fixation is done with the help of metals. Majorly stainless steel, titanium and its alloy.

However, these implants and devices are not biodegradable, increase hospitalization time, vet care cost, chances of infection, long period of healing time and complications. Moreover, due to mismatching between the mechanical properties of natural bone and these implants or devices, the loads and mechanical forces are retained by implants and are not directly transferred to the fractured site. This can cause loosening of the bone implant and unwanted bone resorption (Sheikh et al. 2015).

The gold standard for fracture repair is autologous bone grafting and it has all the necessary characteristics required for bone healing, such as osteoinductivity, osteoconductivity and osteogenicity. However, there are concerns of this approach also, such as; donor site morbidity, limited blood supply, increased bone resorption during healing, surgical, anatomical and structural limitations (Sheikh et al. 2015). Second option is allograft, but there are concerns with this, such as; sterilization, delayed graft incorporation, tissue availability, graft cost, long term graft strength and disease transmission. Another alternate to autograft is xenografts; they have osteoconductive and osteoinductive properties, high availability and low cost. But there are many risks are associated with it such as immunogenicity, tissue rejection and transmission of zoonotic and infectious diseases (Oryan et al. 2014).

Nowadays with the advancement of technology, sound methodologies of surgery and excellent supportive treatment fracture fixation have reached a high standard. However, there are many problems which are un-addressed such as loss of vascularization, bone defect, bone loss, lack of stability, infections, soft tissue damage and tumors. So, in contrast to these advance technology approaches addition of regenerative medicine may be a game changer and in combination with advance technology this may be the ultimate solution in challenging cases (Winkler et al. 2018).

In bone regeneration one of the largest unsolved challenges are bone defects. In order to fill these kinds of defects, biomaterials are used. They provide both structural and functional support in the replacement of the lost bone. Biomaterials are natural or synthetic materials which are used for therapeutic purposes. Once they are placed inside the body they interact in physical, biological and chemical way with recipient’s system to accelerate the healing process (Winkler et al. 2018).

As the bone grafts has some limitations which led the researchers to explore the other options which includes growth factors, demineralized bone matrix, gene therapy, allogenic grafts, bone morphogenetic proteins and bone substitutes, but all of these have their advantages and limitations. In past years Platelet-rich plasma (PRP) has gained popularity as an alternate autologous treatment for bone repair. Growth factors which are released from PRP can activate the proliferation and chemotactic movement of chondrocytes, osteoblasts and mesenchymal cells and angiogenesis. The higher concentrations of this growth factor can increase the rate of bone healing, while lack of these factor can ultimately leads towards nonunion (Esther et al. 2021). 

Another biomaterial which gained the importance in recent years because of its regenerative properties is platelet rich fibrin (PRF). PRF is second generation platelet derivative developed by Choukroun et al. PRF consists on platelets, cytokines, adhesive protein and leukocytes. Leukocytes secrete huge quantity of growth factors (Elhamshary et al. 2022). PRF is rich in growth factors which are vital for bone healing, such as fibrin, hyaluronan and fibronectin which are useful for cell adhesion promotion. It can be utilized as a single biomaterial or in combination to acceleration bone healing process. It also improves immunity, epithelialization and promotes angiogenesis (Pavlovic et al. 2021). 

Another biomaterial which increases the healing is chitosan; a naturally occurring biopolymer which is derived from chitin. It is mainly composed of N-acetyl glucosamine and glucosamine. Its molecular weight varies from 300-1000 kilodalton (kDa) depending on its processing methods and source. Chitosan in degraded by papain, chitosanase and lysozymes in vitro, while in vivo degradation is by hydrolysis and by the action of lysozymes. It is biocompatible and because of its porous micro architecture structure it is being used in preparation of structures and scaffolds. It is also being used in combinations with other biomaterials such as calcium phosphate, collagen, silica and sulfate groups to enhance bone healing. As it is biodegradable, biocompatible and much adhesive in nature, chitosan has been widely used in many fields such as tissue engineering, pharmaceutical application, biomedical and surgical (Sheikh et al. 2015). 

Research on the use of biomaterials in was initiated in the early nineties (90s) and was used in different areas. However, major transition was seen 2000 on the use of biomaterials as world started using bio absorbable material or bio inert materials in regenerative biomedical research. In some researches biological sciences are used in combination with biomaterial science (Iftikhar et al. 2021). In late 1940s and 1950s first biomaterials were applied in medicine which we know them today.

Nowadays there a huge market of medical devices and biomaterials having worth more than 300 billion USD that helps in improving the quality of life and saves lives (Ratner 2019).
Majority of the work on biological science and biomaterials science has been done in the field of humans. However, their application in veterinary sciences is still very less in Pakistan, especially in field of orthopedic surgery. So, this study is designed to understand the healing pattern of different biomaterials in fracture repair as well as their comparison with each other. This study will further open the doors for the use of biomaterial in veterinary practice to hasten the fracture healing process.

Keeping these points in view, this study is planned to investigate the chitosan, platelet rich plasma (PRP) and platelet rich fibrin (PRF) as base line study for fracture healing in a rabbit model.
Healthy rabbits (n=36) were purchased from the market and divided into 6 groups; A, B, C, D, E and F. Each group had 6 rabbits randomly. Basic health parameters were assessed in all rabbits including temperature, pulse, respiration, weight measurement, preoperative blood profile and X-ray was performed. A 3mm hole was drilled on the midshaft of tibia with the help of manual drill. PRP, PRF and chitosan were applied on fractured site individually and in combination. Data was collected preoperatively and postoperatively at different intervals upto 8 weeks postoperatively to evaluate the healing process which included; Physical examination, radiographic evaluation, calcium, phosphorus, serum ALP and rabbit osteocalcin were measured.

The groups treated with combination of biomaterials (PRP + Chitosan and PRF + Chitosan) showed better bone regeneration in comparison with groups treated with individual biomaterials

From this study we were able to standardize the preparation of PRP and PRF under local conditions in Pakistan. It opens a new way of treatment of fractures and technological advancement in the field of veterinary orthopedic surgery within Pakistan.

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