Recombinant human platelet-derived growth factor-BB versus autologous bone graft in foot and ankle fusion: A systematic review and meta-analysis

Effectiveness of synthetic versus autologous bone grafts in foot and ankle surgery: a systematic review and meta-analysis

BACKGROUND

All orthopaedic procedures, comprising foot and ankle surgeries, seemed to show a positive trend, recently. Bone grafts are commonly employed to fix bone abnormalities resulting from trauma, disease, or other medical conditions. This study specifically focuses on reviewing the safety and efficacy of various bone substitutes used exclusively in foot and ankle surgeries, comparing them to autologous bone grafts.

METHODS

The systematic search involved scanning electronic databases including PubMed, Scopus, Cochrane online library, and Web of Science, employing terms like 'Bone substitute,' 'synthetic bone graft,' 'Autograft,' and 'Ankle joint.' Inclusion criteria encompassed RCTs, case-control studies, and prospective/retrospective cohorts exploring different bone substitutes in foot and ankle surgeries. Meta-analysis was performed using R software, integrating odds ratios and 95% confidence intervals (CI). Cochrane's Q test assessed heterogeneity.

RESULTS

This systematic review analyzed 8 articles involving a total of 894 patients. Out of these, 497 patients received synthetic bone grafts, while 397 patients received autologous bone grafts. Arthrodesis surgery was performed in five studies, and three studies used open reduction techniques. Among the synthetic bone grafts, three studies utilized a combination of recombinant human platelet-derived growth factor BB homodimer (rhPDGF-BB) and beta-tricalcium phosphate (β-TCP) collagen, while four studies used hydroxyapatite compounds. One study did not provide details in this regard. The meta-analysis revealed similar findings in the occurrence of complications, as well as in both radiological and clinical evaluations, when contrasting autografts with synthetic bone grafts.

CONCLUSION

Synthetic bone grafts show promise in achieving comparable outcomes in radiological, clinical, and quality-of-life aspects with fewer complications. However, additional research is necessary to identify the best scenarios for their use and to thoroughly confirm their effectiveness.

LEVELS OF EVIDENCE

Level II.

Advances in bone regeneration with growth factors for spinal fusion: A literature review

Bone tissue is regenerated via the spatiotemporal involvement of various cytokines. Among them, the bone morphogenetic protein (BMP), which plays a vital role in the bone regeneration process, has been applied clinically for the treatment of refractory orthopedic conditions. Although BMP therapy using a collagen carrier has shown efficiency in bone regeneration over the last two decades, a major challenge-considerable side effects associated with the acute release of high doses of BMPs-has also been revealed. To improve BMP efficiency, the development of new carriers and biologics that can be used in conjunction with BMPs is currently underway. In this review, we describe the current status and future prospects of bone regeneration therapy, with a focus on BMPs. Furthermore, we outline the characteristics and molecular signaling pathways involving BMPs, clinical applications of BMPs in orthopedics, clinical results of BMP use in human spinal surgeries, drugs combined with BMPs to provide synergistic effects, and novel BMP carriers.

Characterizing the host response to rhPDGF-BB in a rat spinal arthrodesis model

BACKGROUND

Due to the constraints surrounding autograft bone, surgeons have turned to osteoinductive agents to augment spinal fusion. Reports of complications and questionable efficacy slowed the adoption of these alternatives. Recombinant human platelet-derived growth factor B homodimer (rhPDGF-BB) has been Food and Drug Administration (FDA)-approved (Augment) to promote fusion in other areas of orthopedics, but its characterization in spine fusion has not yet been tested. The purpose of this study is to characterize the host response to PDGF-BB in vivo.

METHODS

Eighty female Fischer rats underwent L4-5 posterolateral fusion using one of four implant types: (a) iliac crest syngeneic allograft harvested from syngeneic donors, (b) β-TCP/bovine collagen matrix (β-TCP/Col) with sodium acetate buffer, (c) β-TCP/Col with 0.3 mg/mL "low dose," or (d) β-TCP/Col with 3.0 mg/mL "high dose" of rhPDGF-BB. Animals underwent magnetic resonance imaging (MRI) and serum cytokine quantification at 4, 7, 10, and 21 days, postoperatively. Tissues were processed for immunofluorescence staining for Ki67 and von Willebrand factor (vWF) to assess neovascularization.

RESULTS

MRI demonstrated no differences in fluid accumulation among the four treatment groups at any of the time points. Serum cytokine analysis showed no clinically significant differences between treatment groups in 20 of the 27 cytokines. Inflammatory cytokines IFN-γ, IL-1β, IL-18, MCP-1, MIP-1α, TNF-α were not induced by rhPDGF-BB. Histology showed no differences in cell infiltration, and Ki67 and vWF immunofluorescence staining was similar among groups.

CONCLUSIONS

rhPDGF-BB delivered with a β-TCP/Col matrix exerts no exaggerated systemic or local host inflammatory response when compared to iliac crest syngeneic allograft bone or the control carrier. rhPDGF-BB mixed with a β-TCP/Col matrix could be a viable and safe biologic alternative to syngeneic allograft in spine fusion. Further studies need to be performed to evaluate efficacy in this setting.

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

Limited Evidence for Biological Adjuvants in Hindfoot Arthrodesis: A Systematic Review and Meta-Analysis of Clinical Comparative Studies

BACKGROUND

The purpose of the present study was to evaluate the efficacy of biological adjuvants in patients managed with hindfoot arthrodesis.

METHODS

A systematic review of the PubMed and Embase databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines with use of specific search terms and eligibility criteria. Assessment of evidence was threefold: level of evidence by criteria as described in The Journal of Bone & Joint Surgery, quality of evidence according to the Newcastle-Ottawa scale, and conflicts of interest. Meta-analysis was performed with fixed-effects models for studies of low heterogeneity (I2 < 25%) and with random-effects models for studies of moderate to high heterogeneity (I2 ≥ 25%).

RESULTS

A total of 1,579 hindfeet were recruited across all studies, and 1,527 hindfeet were recorded as having completed treatment and follow-up visits. The duration of follow-up ranged from 2.8 to 43 months. Twelve of the 17 included studies comprised patients with comorbidities associated with reduced healing capacity. Based on the random-effects model for nonunion rates for autograft versus allograft, the risk ratio was 0.82 (95% CI, 0.13 to 5.21; I2 = 56%; p = 0.83) in favor of lower nonunion rates for autograft. Based on the random-effects model for rhPDGF/β-TCP versus autograft, the risk ratio was 0.90 (95% CI, 0.74 to 1.10; I2 = 59%; p = 0.30) in favor of lower nonunion rates for rhPDGF/β-TCP.

CONCLUSIONS

There is a lack of data to support the meaningful use of biological adjuvants as compared with autograft/allograft for hindfoot arthrodesis. The meta-analysis favored the use of autograft when compared with allograft but favored rhPDGF/β-TCP when compared with autograft in the short term.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Evaluation of lumbar spinal fusion utilizing recombinant human platelet derived growth factor-B chain homodimer (rhPDGF-BB) combined with a bovine collagen/β-tricalcium phosphate (β-TCP) matrix in an ovine model

BACKGROUND CONTEXT

While the clinical effectiveness of recombinant human Platelet Derived Growth Factor-B chain homodimer combined with collagen and β-tricalcium phosphate (rhPDGF-BB + collagen/β-TCP) treatment for indications involving hindfoot and ankle is well-established, it is not approved for use in spinal interbody fusion, and the use of autograft remains the gold standard.

PURPOSE

The purpose of this study was to compare the effects of rhPDGF-BB + collagen/β-TCP treatment on lumbar spine interbody fusion in an ovine model to those of autograft bone and collagen/β-TCP treatments using biomechanical, radiographic, and histological assessment techniques.

STUDY DESIGN

Thirty-two skeletally mature Columbian Rambouillet sheep were used to evaluate the safety and effectiveness of rhPDGF-BB + collagen/β-TCP matrix in a lumbar spinal fusion model. Interbody polyetheretherketone (PEEK) cages contained either autograft, rhPDGF-BB + collagen/β-TCP, collagen/β-TCP matrix, or left empty.

METHODS

Animals were sacrificed 8- or 16-weeks post-surgery. Spinal fusion was evaluated via post-sacrifice biomechanical, micro-computed tomography (μCT), and histological analysis. Outcomes were statistically compared using a two-way analysis of variance (ANOVA) with an alpha value of 0.05 and a Tukey post-hoc test.

RESULTS

There were no statistically significant differences between groups within treatment timepoints for flexion-extension, lateral bending, or axial rotation range of motion, neutral zone, neutral zone stiffness, or elastic zone stiffness. μCT bone volume fraction was significantly greater between treatment groups independent of timepoint where Autograft and rhPDGF-BB + collagen/β-TCP treatments demonstrated significantly greater bone volume fraction as compared to collagen/β-TCP (P = .026 and P = .038, respectively) and Empty cage treatments (P = .002 and P = .003, respectively). μCT mean bone density fraction was most improved in rhPDGF-BB + collagen/β-TCP specimens at the 8 week and 16-week timepoints as compared to all other treatment groups. There were no statistically significant differences in histomorphometric measurements of bone, soft tissue, or empty space between rhPDGF-BB + collagen/β-TCP and autograft treatments.

CONCLUSIONS

The results of this study indicate that the use of rhPDGF-BB combined with collagen/β-TCP promotes spinal fusion comparable to that of autograft bone.

CLINICAL SIGNIFICANCE

The data indicate that rhPDGF-BB combined with collagen/β-TCP promotes spinal fusion comparably to autograft bone treatment and may offer a viable alternative in large animal spinal fusion. Future prospective clinical studies are necessary to fully understand the role of rhPDGF-BB combined with collagen/β-TCP in human spinal fusion healing.

Impact of Bone Graft on Fusion Rates in Primary Open Ankle Arthrodesis Fixated With Cannulated Screws: A Systematic Review

There is currently no consensus on the importance of bone graft use in ankle arthrodesis. Despite this, bone graft is widely used. We aimed to summarize the available literature on primary open ankle arthrodesis fixated with cannulated screws in order to assess the importance of bone graft in achieving more favorable rates of fusion. PubMed and Embase were queried for articles reporting on primary open ankle arthrodesis fixated with cannulated screws which specified use or non-use of bone graft. Pooled data analysis was performed. Modified Coleman Methodology Scores were calculated to assess reporting quality. Twenty-seven studies met our inclusion criteria and were divided into three groups: no bone graft (NBG), fibular onlay with bone graft (FOBG), and use of bone graft (BG). All three groups had comparable fusion rates of 94.7%, 95.3%, and 95.1% respectively (p = .98). Number needed to treat was 7 and Absolute Risk Reduction was 14.8%. The reviewed literature was largely of moderate quality, with an overall Coleman score of 60.6 and no significance between the 3 groups (p = .93). In conclusion, primary open ankle arthrodesis fixated with cannulated screws generally had favorable fusion rates, and bone graft use did not have a significant effect on union rates. The available literature suggests that bone graft may not be needed in routine tibiotalar arthrodesis in low-risk patients. It may more significantly impact patients who are at high-risk of fusion failure, and dedicated research on this high-risk subset of patients is required.

Growth Factors, Carrier Materials, and Bone Repair

This chapter provides an overview of the growth factors active in bone regeneration and healing. Both normal and impaired bone healing are discussed, with a focus on the spatiotemporal activity of the various growth factors known to be involved in the healing response. The review highlights the activities of most important growth factors impacting bone regeneration, with a particular emphasis on those being pursued for clinical translation or which have already been marketed as components of bone regenerative materials. Current approaches the use of bone grafts in clinical settings of bone repair (including bone grafts) are summarized, and carrier systems (scaffolds) for bone tissue engineering via localized growth factor delivery are reviewed. The chapter concludes with a consideration of how bone repair might be improved in the future.

Cytokines and Growth Factors

Several cytokines have been used to treat autoimmune diseases, viral infections, and cancer and to regenerate the skin. In particular, interferons (INFs) have been used to treat cancer, hepatitis B and C, and multiple sclerosis, while interleukins (ILs) and tumor necrosis factors (TNFs) have been used in the management of different types of cancer. Concerning the hematopoietic growth factors (HGFs), epoetin has been used for anemia, whereas the colony-stimulating factors (CSFs) have been used for neutropenia. Other growth factors have been extensively explored, although most still need to demonstrate in vivo clinical relevance before reaching the market.This chapter provides an overview on the therapeutic applications of biological medicines containing recombinant cytokines and growth factors (HGFs and others). From this review, we concluded that the clinical relevance of recombinant cytokines has been increasing. Since the 1980s, the European Medicines Agency (EMA) and/or Food and Drug Administration (FDA) have approved 89 biological medicines containing recombinant cytokines. Among these, 18 were withdrawn, 24 are biosimilars, and 18 are orphans.So far, considerable progress has been made in discovering new cytokines, additional cytokine functions, and how they interfere with human diseases. Future prospects include the approval of more biological and biosimilar medicines for different therapeutic applications.