Background and rationale of platelet gel in orthopaedic surgery

Platelet concentrate as an additive to bone allografts: a laboratory study using an uniaxial compression test

Chemical cleaning procedures of allografts are destroying viable bone cells and denaturing osteoconductive and osteoinductive proteins present in the graft. The aim of the study was to investigate the mechanical differences of chemical cleaned allografts by adding blood, clotted blood; platelet concentrate and platelet gel using a uniaxial compression test. The allografts were chemically cleaned, dried and standardized according to their grain size distribution. Uniaxial compression test was carried out for the four groups before and after compacting the allografts. No statistically significant difference was found between native allografts, allografts mixed with blood, clotted blood, platelet concentrate and platelet concentrate gel regarding their yield limit after compaction. The authors recommend to chemical clean allografts for large defects, optimize their grain size distribution and add platelet concentrate or platelet rich plasma for enhancing as well primary stability as well bone ingrowth.

Influence of calcium salts and bovine thrombin on growth factor release from equine platelet-rich gel supernatants

Objective: To compare five activation methods in equine platelet-rich plasma (PRP) by determination of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor beta 1 (TGF-β1) concentrations in platelet-rich gel (PRG) supernatants.

Methods: Platelet-rich plasma from 20 horses was activated by calcium chloride (CC), calcium gluconate (CG), bovine thrombin (BT), and their combinations, BTCC and BTCG. Both growth factor concentrations in PRG supernatants were measured by ELISA and compared with plasma and platelet ly-sates (PL) over time.

Results: Growth factor concentrations were significantly lower in plasma and higher for all PRG supernatants. Platelet lysates contained a significantly lower concentration of PDGF-BB than PRG supernatants and a significantly higher concentration of TGF-β1 than PRG supernatants. Clots from PRP activated with sodium salts were more stable over time and had significant growth factor release, whereas CC produced gross salt deposition. Significant correlations were noticed for platelet with leukocyte concentrations in PRP (rs: 0.76), platelet counts in PRP with TGF-β1 concentrations in PRG supernatants (rs: 0.86), platelet counts in PRP with PDGF-BB concentrations in PRG super-natants (rs: 0.78), leukocyte counts in PRP with TGF-β1 concentrations in PRG supernatants (rs: 0.76), and PDGF-BB concentrations with activating substances (rs: 0.72).

Clinical significance: Calcium gluconate was the better substance to induce PRP activation. It induced growth factor release free from calcium precipitates in the clots. Use of BT alone or combined with calcium salts was not advantageous for growth factor release.

Investigating the effect of intra-articular PRP injection on pain and function improvement in patients with distal radius fracture

INTRODUCTION

Distal radius fractures are common injuries that cause pain and disability. There is a clear need for biomedical engineering research to develop novel strategies to improve functional results following intra-articular distal radius fractures. However, no pharmacotherapeutic agent has been investigated to resolve this problem. The aim of this study was to evaluate whether the platelet-rich plasma (PRP) can be considered a novel additional therapy to improve the outcomes of this injury.

HYPOTHESIS

Pain reduction and functional improvement can be noticed after PRP use in distal radius fracture.

MATERIALS AND METHODS

A randomized trial study was designed with 30 patients who had intra-articular distal radius fractures (Frykman type 3, 4, 7, 8). Closed reduction and percutaneous pinning under guide of fluoroscopy were done for them. Fifteen cases received intra-articular autologus PRP. Patients were followed for 3 and 6 months and "patient-rated wrist evaluation" (PRWE) questionnaire was completed and range of motion of the wrist was measured.

RESULTS

The mean of pain score and the score of specific and usual activities at 3 months follow-up in the case group and in the control group were (8.33 versus 19.67), (10.66 versus 26.8), and (6.2 versus 13.4), respectively. The mean of pain score and score of specific and usual activities at 6 months follow-up in the case group and in the control group were (3.6 versus 12), (3 versus 15.7), and (1.2 versus 6.8), respectively. The case group was significantly different from the control group. The mean of loss of flexion and extension of the wrist at 3 months follow-up in the case group was significantly different from the control group as well.

CONCLUSION

PRP may have significant effect on reduction of pain and amount of difficulty in functions, including specific and usual activities after intra-articular distal radius fractures.

LEVEL OF EVIDENCE

Level III, Therapeutic trial.

Formation of blood clot on biomaterial implants influences bone healing

The first step in bone healing is forming a blood clot at injured bones. During bone implantation, biomaterials unavoidably come into direct contact with blood, leading to a blood clot formation on its surface prior to bone regeneration. Despite both situations being similar in forming a blood clot at the defect site, most research in bone tissue engineering virtually ignores the important role of a blood clot in supporting healing. Dental implantology has long demonstrated that the fibrin structure and cellular content of a peri-implant clot can greatly affect osteoconduction and de novo bone formation on implant surfaces. This article reviews the formation of a blood clot during bone healing in relation to the use of platelet-rich plasma (PRP) gels. It is implicated that PRP gels are dramatically altered from a normal clot in healing, resulting in conflicting effect on bone regeneration. These results indicate that the effect of clots on bone regeneration depends on how the clots are formed. Factors that influence blood clot structure and properties in relation to bone healing are also highlighted. Such knowledge is essential for developing strategies to optimally control blood clot formation, which ultimately alter the healing microenvironment of bone. Of particular interest are modification of surface chemistry of biomaterials, which displays functional groups at varied composition for the purpose of tailoring blood coagulation activation, resultant clot fibrin architecture, rigidity, susceptibility to lysis, and growth factor release. This opens new scope of in situ blood clot modification as a promising approach in accelerating and controlling bone regeneration.

Characteristics of platelet gels combined with silk

Platelet gel, a fibrin network containing activated platelets, is widely used in regenerative medicine due the capacity of platelet-derived growth factors to accelerate and direct healing processes. However, limitations to this approach include poor mechanical properties, relatively rapid degradation, and the lack of control of release of growth factors at the site of injection. These issues compromise the ability of platelet gels for sustained function in regenerative medicine. In the present study, a combination of platelet gels with silk fibroin gel was studied to address the above limitations. Mixing sonicated silk gels with platelet gels extended the release of growth factors without inhibiting gel-forming ability. The released growth factors were biologically active and their delivery was modified further by manipulation of the charge of the silk protein. Moreover, the silk gel augmented both the rheological properties and compressive stiffness of the platelet gel, tuned by the silk concentration and/or silk/platelet gel ratio. Silk-platelet gel injections in nude rats supported enhanced cell infiltration and blood vessel formation representing a step towards new platelet gel formulations with enhanced therapeutic impact.

Preparation method and growth factor content of platelet concentrate influence the osteogenic differentiation of bone marrow stromal cells

BACKGROUND AIMS

An extensive debate about the clinical benefits of autologous platelet concentrates used as a treatment option for patients with orthopedic injuries is ongoing. The aim of this study was to determine whether different compositions of platelet concentrates may affect the osteogenic differentiation of bone marrow stromal cells (BMSC).

METHODS

Pure platelet-rich plasma (P-PRP) and leukocyte-PRP (L-PRP) were characterized for platelet and leukocyte content. As an indicative marker of the delivery of growth factors (GFs), the release of basic fibroblast growth factor (bFGF) from platelet gel (PG) was measured at 1, 18, 48 and 72 h and at 7 d. The ability of different PGs to induce proliferation and differentiation of BMSC was evaluated by using bioactivity assays.

RESULTS

The platelet recovery was significantly higher in L-PRP, either fresh or frozen. PGs derived from L-PRP and P-PRP showed significant differences in terms of bFGF release and biological activity. bFGF release was faster both in fresh and frozen L-PRP preparations. Moreover, L-PRP samples were able to induce a significantly higher proliferation of BMSC compared with P-PRP or PPP samples. Even though all PG preparations allowed the deposition of mineral nodules in BMSC cultures, the mineralization activity correlated significantly with bFGF levels.

CONCLUSIONS

The biological activity of platelet concentrates differs according to preparation technique, which affects platelet and leukocyte content and GF availability. Because GF levels are not always optimal in subjects with defective bone healing, composition and bioactivity of PRP should be analyzed to test the reliability and potential effectiveness of the regenerative treatment.

Serum levels of fibroblast growth factor 2 in children with orthopedic diseases: potential role in predicting bone healing

Fibroblast growth factor 2 (FGF-2) plays an important role in the early phases of bone healing. In this study, we measured FGF-2 serum levels in 88 children undergoing surgical treatment for congenital (n = 49) or acquired (n = 39) orthopedic conditions, which were associated (n = 35) or not (n = 53) with bone lesions, to assess whether serum levels of FGF-2 varied according to the underlying disease and may predict clinical outcomes. FGF-2 serum levels were significantly lower in patients who did not heal after surgery (p = 0.008). Diagnostic accuracy was validated statistically, and the ROC curve provided a threshold value useful in discriminating good versus poor outcomes. The relationship between FGF-2 and bone healing was supported by in vitro experiments. A mineralization assay was performed on bone marrow stromal cells from three patients with congenital pseudarthrosis, who had low serum levels of FGF-2 and a poor clinical outcome after surgical treatment. Autologous serum alone was not sufficient to induce in vitro mineralization, but it did occur when cells were cultured with different sources of exogenous growth factors (GFs), including recombinant FGF-2 and homologous serum collected from children with fractures, high FGF-2 levels, and a good clinical outcome. In conclusion, our findings suggest that osteoinductive GFs are essential for bone repair, and that the amount of circulating FGF-2 may predict bone healing.

Skeletal tissue regeneration: current approaches, challenges, and novel reconstructive strategies for an aging population

Loss of skeletal tissue as a consequence of trauma, injury, or disease is a significant cause of morbidity with often wide-ranging socioeconomic impacts. Current approaches to replace or restore significant quantities of lost bone come with substantial limitations and inherent disadvantages that may in themselves cause further disability. In addition, the spontaneous repair capacity of articular cartilage is limited; thus, investigation into new cartilage replacement and regeneration techniques are warranted. Along with the challenges of an increasingly aging demographic, changing clinical scenarios and rising functional expectations provide the imperative for new, more reliable skeletal regeneration strategies. The science of tissue engineering has expanded dramatically in recent years, notably in orthopedic applications, and it is clear that new approaches for de novo skeletal tissue formation offer exciting opportunities to improve the quality of life for many, particularly in the face of increasing patient expectations. However, significant scientific, financial, industrial, and regulatory challenges should be overcome before the successful development of an emergent tissue engineering strategy can be realized. We outline current practice for replacement of lost skeletal tissue and the innovative approaches in tissue regeneration that have so far been translated to clinical use, along with a discussion of the significant hurdles that are presented in the process of translating research strategies to the clinic.