**1. Introduction**

Virtually, all the cells of the musculoskeletal tissues are mechano-sensive and experience mechanical stress through the distortion of the extracellular matrix (ECM) complex. The exposure of musculoskeletal cells to nonphysiological stimuli, either mechanical or biochemical, leads to swings of the tissue pendulum towards profound alterations of components of the ECM both cellular and acellular as well as the physical and chemical properties of the ECM. Such stimuli lead to cell microenvironment damage, non-resolving inflammation and disease. In addition to specific features of each tissue (vascularization, innervation and type of cells), abnormal biomechanical loading as obesity, a sedentary lifestyle leading to metabolic disorders, joint injury or high intensity and prolonged sports activities make musculoskeletal tissues vulnerable to injury. Through such overuse or disuse, these nonphysiological stimuli may well produce a consequential disruption in tissue homeostasis (**Figure 1**).

2- and 2.5-fold higher than blood and no leukocytes (PRGF®-Endoret®, BTI-Biotechnology

PRP Injections in Orthopaedic Surgery: Why, When and How to Use PRP Dynamic Liquid Scaffold…

gous formulations whose versatility endows this technology with a myriad of applications in

This chapter addresses the following questions: Why would surgeons want to harness the biological features of PRP in the operating theatre? When are PRP injections indicated as an adjuvant to? How should the injections be introduced to obtain beneficial outcomes in surgery?

The physicochemical features of PRP liquid formulation, once activated, make it appropriate to reach wide areas of soft and hard tissues such as the tendons, muscles, ligaments, menisci, cartilage and bone. Platelet growth factors and fibrin, together with plasmatic growth factors (HGF, IGF-1) present within PRP, stimulate in a pleiotropic manner cell proliferation and migration, angiogenesis, synthesis and deposition of ECM components and tissue remodelling in the musculoskeletal tissues [6–8]. The surgical site is opened in the normal manner, and in the following 2: 4 minutes, the liquid-activated formulation must be injected as a solution into soft tissues. Because of its local and gradual activation and homogeneous distribution and interaction with the ECM of different tissues, it is converted into a matrix-like malleable transient structure [2]. There is a direct interplay between components of a tissue's ECM (collagens, glycosaminoglycans and adhesive proteins) and the adhesive proteins and growth factors released gradually from the degrading fibrin clot which will influence cellular growth, differentiation and morphogenesis [9]. Therefore, the injection of PRP in its liquid formulation delivers growth factors locally and simultaneously mimics and amplifies the spontaneous healing response in injured areas and in special cell niches, which would otherwise be inaccessible. This in situ generated and moulded plastic nano-scaffold of fibrin interacts with ECM proteins and cells, binding to fibronectin [10], generating a transient three-dimensional scaffold, which will gradually release growth factors and maintain their concentration at the

The fibrin molecules, together with growth factors, influence and govern the repair mechanisms to reconstruct structures and restore function, both by harnessing local or resident cells and by stimulating cell migration and proliferation, thereby regulating angiogenesis, modulating inflammation, chemoattracting circulating progenitor cells and guiding tissue remodelling [11, 12]. PRP in situ generated nano-scaffold of fibrin offers a biologically active cell-matrix landscape where adhesive proteins, namely, fibrinogen, fibronectin, vitronectin and thrombospondin (TSP-1), facilitate cell adhesion, migration, proliferation and differentiation. Furthermore, by the release of stromal cell-derived factor 1 (SDF-1) which has been entrapped in the fibrin network, the nano-scaffold mediates the chemotaxis of CD34 progenitor cells and mesenchymal stem cells (MSCs) [7, 13, 14]. Once recruited, MSCs or pericytes [15] adhere to a fibrin network and may exert several functions such as tissue organisation, regulating the fate of other circulating and resident progenitor cells [16] and serving as

**2. Reasons to use PRPs as repair process enhancers in orthopaedic** 

offering a variety of autolo-

39

http://dx.doi.org/10.5772/intechopen.76091

Institute, Vitoria-Gasteiz) [2]. PRP can be activated with CaCl2

**surgery: the scientific rationale behind it**

site of the scaffold formation (**Figure 2**)

orthopaedics [3–5].

A new innovative approach to the treatment of acute and chronic sports injuries uses engineering biology assisted by the application of platelet-rich plasma (PRP) in its different formulations. Generally, PRP products can be described as any autologous blood platelet concentrate within a plasma suspension. PRP products include plasma and twofold or greater increases in platelet concentrations above baseline levels: not insignificantly, their concentration of leukocytes and erythrocytes varies widely [1] from a complete absence of these cells to a high concentration of them. In this chapter, the described PRP has a platelet concentration between

**Figure 1.** Both an excess and insufficiency of physical activity associated with factors such as vascular imbalance, intrinsic hereditary risk factors and a novel environment may disrupt the fragile homeostasis maintained by the tenocyte, stromal fibroblast and tissue-resident macrophages. A localised, predominantly catabolic context associated with a high temperature, ECM fragments and acidosis with building up of lactic acid may be the root cause of inflammationdegeneration of the ECM.

2- and 2.5-fold higher than blood and no leukocytes (PRGF®-Endoret®, BTI-Biotechnology Institute, Vitoria-Gasteiz) [2]. PRP can be activated with CaCl2 offering a variety of autologous formulations whose versatility endows this technology with a myriad of applications in orthopaedics [3–5].

**1. Introduction**

38 Plasma Medicine - Concepts and Clinical Applications

degeneration of the ECM.

Virtually, all the cells of the musculoskeletal tissues are mechano-sensive and experience mechanical stress through the distortion of the extracellular matrix (ECM) complex. The exposure of musculoskeletal cells to nonphysiological stimuli, either mechanical or biochemical, leads to swings of the tissue pendulum towards profound alterations of components of the ECM both cellular and acellular as well as the physical and chemical properties of the ECM. Such stimuli lead to cell microenvironment damage, non-resolving inflammation and disease. In addition to specific features of each tissue (vascularization, innervation and type of cells), abnormal biomechanical loading as obesity, a sedentary lifestyle leading to metabolic disorders, joint injury or high intensity and prolonged sports activities make musculoskeletal tissues vulnerable to injury. Through such overuse or disuse, these nonphysiological stimuli

A new innovative approach to the treatment of acute and chronic sports injuries uses engineering biology assisted by the application of platelet-rich plasma (PRP) in its different formulations. Generally, PRP products can be described as any autologous blood platelet concentrate within a plasma suspension. PRP products include plasma and twofold or greater increases in platelet concentrations above baseline levels: not insignificantly, their concentration of leukocytes and erythrocytes varies widely [1] from a complete absence of these cells to a high concentration of them. In this chapter, the described PRP has a platelet concentration between

**Figure 1.** Both an excess and insufficiency of physical activity associated with factors such as vascular imbalance, intrinsic hereditary risk factors and a novel environment may disrupt the fragile homeostasis maintained by the tenocyte, stromal fibroblast and tissue-resident macrophages. A localised, predominantly catabolic context associated with a high temperature, ECM fragments and acidosis with building up of lactic acid may be the root cause of inflammation-

may well produce a consequential disruption in tissue homeostasis (**Figure 1**).

This chapter addresses the following questions: Why would surgeons want to harness the biological features of PRP in the operating theatre? When are PRP injections indicated as an adjuvant to? How should the injections be introduced to obtain beneficial outcomes in surgery?
