Biologic Adjuvants for the Management of Osteochondral Lesions of the Talus

MaCalus V. Hogan, MD, MBA; Justin J. Hicks, MD; Monique C. Chambers, MD, MSL; John G. Kennedy, MD, FRCS

Disclosures

J Am Acad Orthop Surg. 2019;27(3):e105-e111. 

In This Article

Growth Factors and Platelet-rich Plasma

Growth factors are proteins that stimulate the growth and development of tissue. Platelet-rich plasma (PRP) is composed of a patient's own concentrated platelets, which contain over 1,500 growth factors located within the α-granules.[13] These growth factors have several functions including both cartilage growth and extracellular matrix synthesis, which in turn may have the potential to augment cartilage healing and repair (Table 1). It is important to note that the composition of growth factors in PRP varies from person to person and even between repeated preparations within the same individual.[14] Other patient-specific factors and differences in commercial system preparation methods can lead to variations in PRP composition and can make interpretation of the literature challenging.[14]

PRP is not only composed of concentrated platelets but also contains leukocytes and reticulocytes. One cannot ignore these ancillary factors because they can affect the function of PRP. For instance, high concentrations of leukocytes are associated with catabolic cytokines and proinflammatory signaling, which can be detrimental to tissue healing, compared with leukocyte-poor PRP, which in vitro exhibits anabolic effects promoting chondrogenesis.[15] As such, PRP may act as an adjunct to cartilage repair by decreasing inflammatory mediators, increasing collagen and proteoglycan synthesis and degradation, as well as recruiting mesenchymal stem cells (MSCs), which in turn undergo chondrogenesis and synthesize type II collagen.

A preclinical animal model in rabbits demonstrated that osteochondral defects treated with PRP demonstrated improved histological scoring with increased hyaline-like cartilage and improved integration of the osteochondral graft at the cartilage interface.[16] Clinical studies assessing the efficacy of PRP as an adjunct to microfracture of OLT are promising, reporting improved outcomes compared with surgical repair alone (Table 2). However, long-term, level I randomized control trials are needed. The optimal combination of platelets, leukocytes, and erythrocytes among other components of PRP currently is unknown. A maximal efficacious platelet concentration may also be present. Therefore, it is critical that future studies properly characterize and report PRP contents used, to optimize PRP as an adjunct to OLT surgery and accurately interpret findings.

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