Clinical applications of growth factors in bone injuries: experience with BMPs

Masquelet technique using an allogeneic cortical bone graft for a large bone defect: A case report

BACKGROUND

The induced-membrane technique was initially described by Masquelet as an effective treatment for large bone defects, especially those caused by infection. Here, we report a case of chronic osteomyelitis of the radius associated with a 9 cm bone defect, which was filled with a large allogeneic cortical bone graft from a bone bank. Complete bony union was achieved after 14 months of follow-up. Previous studies have used autogenous bone as the primary bone source for the Masquelet technique; in our case, the exclusive use of allografts is as successful as the use of autologous bone grafts. With the advent of bone banks, it is possible to obtain an unlimited amount of allograft, and the Masquelet technique may be further improved based on this new way of bone grafting.

CASE SUMMARY

In this study, we reported a case of repair of a long bone defect in a 40-year-old male patient, which was characterized by the utilization of allograft cortical bone combined with the Masquelet technique for the treatment of the patient's long bone defect in the forearm. The patient's results of functional recovery of the forearm were surprising, which further deepens the scope of application of Masquelet technique and helps to strengthen the efficacy of Masquelet technique in the treatment of long bones indeed.

CONCLUSION

Allograft cortical bone combined with the Masquelet technique provides a new method of treatment to large bone defect.

A BMP-2 sustained-release scaffold accelerated bone regeneration in rats via the BMP-2 consistent activation maintained by a non-sulfate polysaccharide

Bone morphogenetic protein 2 (BMP-2) and a polysaccharide (SUP) were embedded in the calcium phosphate cement (CPC) scaffold, and the bone repair ability was evaluated. The new scaffolds were characterized using x-ray diffraction, Fourier transform-infrared, scanning electron microscopy, and energy dispersive spectroscopy analyses. CPC-BMP2-SUPH scaffold promoted the BMP-2 release by 1.21 folds of the CPC-BMP2 scaffold on day 3. SUP sustained the release of BMP-2 within 21 d. It enhanced alkaline phosphatase activity by 25.9% in comparison to the CPC scaffold. These results suggest that the SUP consistently activated and sustained BMP-2 releasein vitro. Furthermore, the CPC-BMP2-SUPH scaffold activated the BMP-2/Smads and runt-related transcription factor 2 (Runx-2) pathways in MC3T3-E1 cells to up-regulate the levels of osteogenic relative genes (BMP-2, bone sialoprotein, collagen 1, osteocalcin, osteopontin, and Runx-2). Thein vivoresult showed that the bone defect area in the CPC-BMP2-SUPH scaffold-treated Sprague-Dawley rats lessened significantly compared with the CPC group after 4 weeks. CPC-BNP2-SUPH scaffold also improved collagen regeneration in bone. The bone surface and bone volume in the CPC-BMP2-SUPH group improved by 3.68 and 2.17-fold compared with the CPC group, respectively. In conclusion, the CPC-BMP2-SUPH scaffold represents a novel biomaterial capable of accelerating osteoblast differentiation and promoting bone injury repair.

Off-label: The results of adjunctive bone morphogenetic protein for challenging femur fractures; a review of two cases

Background

Although bone morphogenetic proteins (BMPs) are used as an adjunct to promote healing, they may have unintended effects such as heterotopic ossification (HO). The literature is limited regarding the effect of using off-label BMPs for femur fractures.

Case presentation

We report two outcomes after off-label use of BMPs for the treatment of femur fractures and propose a possible explanation for the difference.

Conclusions

BMPs are critical osteoinductive factors in injured bone and muscle that facilitate bony healing. However, it may be important to recognize the potentially negative effects of adding BMP to bone graft material in certain cases to stimulate bone repair. We hope this case series helps surgeons consider the risks and benefits of using BMP for femur fractures, and therefore to decide with caution when BMP is indicated.

Effect on osseointegration of dental implants treated with carboxyethylphosphonic acid and functionalized with BMP-2: preliminary study on a minipig model

Introduction: Rough titanium surfaces biofunctionalised by osteogenic proteins, such as BMP-2, have been shown to accelerate the osseointegration process and reduce waiting times for prosthetic loading. The preclinical study presented here compared the bone in contact with the implant and bone neoformation and density between titanium (Ti) implants with a conventional etched surface (SLA type) and others treated with carboxyethylphosphonic acid (CEPA) and bone morphogenetic protein 2 (BMP-2), after 4 weeks of implantation in the tibia of a minipig model. Methods: Sixteen implants (eight experimental and eight control) of Ti-Al16-V4 with a tapered screw design and internal hexagonal connection were randomly inserted into the tibiae of four minipigs, four in each tibia. The experimental implants were treated with CEPA and BMP-2 and sterilised with gamma radiation (25 KG). The insertion torque was 40 N and primary stability was measured with the Osstell® device (ISQ 64 ± 2.6). Five bone parameters were evaluated: bone in contact with the implant (BIC), bone in contact with the corrected implant (BICc), new bone formation (BV/TV), bone density between threads (BAI/TA) and peri-implant bone density (BAP/TA). A histomorphometric study was performed and the samples were digitised with Adobe Photoshop Cs6. Statistical analysis of the variables was performed using SAS 9.4. Results: After a period of 4 weeks, no significant clinical signs were observed and all implants were integrated. Light microscopy of the experimental group revealed an ICB with no signs of fiber tissue, but with areas of ectopic new bone in the medullary space. Statistical analysis showed significant results for BIC and BICc (p = 0.0001 and p = 0.001, respectively). No statistical signification was found for the other parameters evaluated. Conclusion: Despite the limitations of this study, our results demonstrated that dental implant surfaces treated with CEPA and BMP-2 improve their biological response to osseointegration.

Recombinant human bone morphogenetic protein is a valid alternative to autologous bone graft for long bone non-unions: a systematic review and meta-analysis

OBJECTIVE

To compare the efficacy of recombinant human bone morphogenetic proteins (rhBMPs) and autologous bone graft (ABG) on the healing of long bone non-union.

METHODS

A systematic literature search was conducted on PubMed, Web of Science, Cochrane Library, and CNKI up to December 2021. Two authors independently screened the studies, extracted data, and assessed the quality of the trials. A Meta-analysis was performed using state software (version 12.0).

RESULTS

A total of 14 studies were included in this meta-analysis. Overall, there was no significant difference between the rhBMPs group and the ABG group in terms of healing rate (RR = 1.04, 95% CI = 0.96-1.12, p = 0.365) and healing time (SMD = -0.31, 95% CI = -0.76-0.14, p = 0.175). Subgroup analysis showed rhBMPs lead to higher healing rates (RR = 1.35, 95% CI = 1.17-1.56, p < 0.001), and shorter healing time (SMD = -0.65, 95% CI = -1.08 to -0.22, p = 0.003) in the subgroup of moderate-quality studies. Sensitivity analysis proved that our conclusions were relatively robust. No significant publication bias was recognized in all studies (Begg's test, p = 0.193; Egger's test, p = 0.307).

CONCLUSIONS

RhBMPs or combined with allografts bone, inorganic bone was a valid alternative to ABG for the treatment of long bone non-union.

Characterization of mouse Bmp5 regulatory injury element in zebrafish wound models

Many key signaling molecules used to build tissues during embryonic development are re-activated at injury sites to stimulate tissue regeneration and repair. Bone morphogenetic proteins provide a classic example, but the mechanisms that lead to reactivation of BMPs following injury are still unknown. Previous studies have mapped a large "injury response element" (IRE) in the mouse Bmp5 gene that drives gene expression following bone fractures and other types of injury. Here we show that the large mouse IRE region is also activated in both zebrafish tail resection and mechanosensory hair cell injury models. Using the ability to test multiple constructs and image temporal and spatial dynamics following injury responses, we have narrowed the original size of the mouse IRE region by over 100 fold and identified a small 142 bp minimal enhancer that is rapidly induced in both mesenchymal and epithelial tissues after injury. These studies identify a small sequence that responds to evolutionarily conserved local signals in wounded tissues and suggest candidate pathways that contribute to BMP reactivation after injury.

Gene transfection achieved by utilizing antibacterial calcium phosphate nanoparticles for enhanced regenerative therapy

Protamine-coated multi-shell calcium phosphate (CaP) was developed as a non-viral vector for tissue regeneration therapy. CaP nanoparticles loaded with different amounts of plasmid DNA encoding bone morphogenetic protein 2 (BMP-2) and insulin-like growth factor 1 (IGF-1) were used to treat MC3T3E1 cells, and the yield of the released BMP-2 or IGF-1 was measured using ELISA 3 days later. Collagen scaffolds containing CaP nanoparticles were implanted into rat cranial bone defects, and BMP-2 and IGF-1 yields, bone formation, and bone mineral density enhancement were evaluated 28 days after gene transfer. The antibacterial effects of CaP nanoparticles against Streptococcus mutans and Aggregatibacter actinomycetemcomitans increased with an increase in the protamine dose, while they were lower for Staphylococcus aureus and Porphyromonas gingivalis. In the combination treatment with BMP-2 and IGF-1, the concentration ratio of BMP-2 and IGF-1 is an important factor affecting bone formation activity. The calcification activity and OCN mRNA of MC3T3E1 cells subjected to a BMP-2:IGF-1 concentration ratio of 1:4 was higher at 14 days. During gene transfection treatment, BMP-2 and IGF-1 were released simultaneously after gene transfer; the loaded dose of the plasmid DNA encoding IGF-1 did not impact the BMP-2 or IGF-1 yield or new bone formation ratio in vitro and in vivo. In conclusion, two growth factor-releasing systems were developed using an antibacterial gene transfer vector, and the relationship between the loaded plasmid DNA dose and resultant growth factor yield was determined in vitro and in vivo.

Medium-Intensity Treadmill Exercise Exerts Beneficial Effects on Bone Modeling Through Bone Marrow Mesenchymal Stromal Cells

As a type of multipotential cells, bone marrow mesenchymal stromal cells (BMMSCs) can differentiate into chondrocytes, osteoblasts, and adipocytes under different loading condition or specific microenvironment. Previous studies have shown that BMMSCs and their lineage-differentiated progeny (for example, osteoblasts), and osteocytes are mechanosensitive in bone. The appropriate physical activity and exercise could help attenuate bone loss, effectively stimulate bone formation, increase bone mineral density (BMD), prevent the progression of osteoporosis, and reduce the risk of bone fractures. Bone morphogenetic protein (BMP) is originally discovered as a protein with heterotopic bone-inducing activity in the bone matrix that exerts a critical role in multiple stages of bone metabolism. In the present study, the medium-intensity treadmill exercise enhanced bone formation and increased osteocalcin (OCN) and osteopontin (OPN) mRNA expression as well as activation of the BMP-Smad signaling pathway in vivo. In order to investigate the effect of a BMP-Smad signaling pathway, we injected mice with activated enzyme inhibitors (LDN-193189HCL) and subjected the mice to treadmill exercise intervention. LDN-193189HCL attenuated the BMD and bone mass mediated by medium-intensity exercise and BMP-Smad signaling pathway.

Role of Prx1-expressing skeletal cells and Prx1-expression in fracture repair

The healing capacity of bones after fracture implies the existence of adult regenerative cells. However, information on identification and functional role of fracture-induced progenitors is still lacking. Paired-related homeobox 1 (Prx1) is expressed during skeletogenesis. We hypothesize that fracture recapitulates Prx1's expression, and Prx1 expressing cells are critical to induce repair. To address our hypothesis, we used a combination of in vivo and in vitro approaches, short and long-term cell tracking analyses of progenies and actively expressing cells, cell ablation studies, and rodent animal models for normal and defective fracture healing. We found that fracture elicits a periosteal and endosteal response of perivascular Prx1+ cells that participate in fracture healing and showed that Prx1-expressing cells have a functional role in the repair process. While Prx1-derived cells contribute to the callus, Prx1's expression decreases concurrently with differentiation into cartilaginous and bone cells, similarly to when Prx1+ cells are cultured in differentiating conditions. We determined that bone morphogenic protein 2 (BMP2), through C-X-C motif-ligand-12 (CXCL12) signaling, modulates the downregulation of Prx1. We demonstrated that fracture elicits an early increase in BMP2 expression, followed by a decrease in CXCL12 that in turn down-regulates Prx1, allowing cells to commit to osteochondrogenesis. In vivo and in vitro treatment with CXCR4 antagonist AMD3100 restored Prx1 expression by modulating the BMP2-CXCL12 axis. Our studies represent a shift in the current research that has primarily focused on the identification of markers for postnatal skeletal progenitors, and instead we characterized the function of a specific population (Prx1+ cells) and their expression marker (Prx1) as a crossroad in fracture repair. The identification of fracture-induced perivascular Prx1+ cells and regulation of Prx1's expression by BMP2 and in turn by CXCL12 in the orchestration of fracture repair, highlights a pathway in which to investigate defective mechanisms and therapeutic targets for fracture non-union.

Advances on Bone Substitutes through 3D Bioprinting

Reconstruction of bony defects is challenging when conventional grafting methods are used because of their intrinsic limitations (biological cost and/or biological properties). Bone regeneration techniques are rapidly evolving since the introduction of three-dimensional (3D) bioprinting. Bone tissue engineering is a branch of regenerative medicine that aims to find new solutions to treat bone defects, which can be repaired by 3D printed living tissues. Its aim is to overcome the limitations of conventional treatment options by improving osteoinduction and osteoconduction. Several techniques of bone bioprinting have been developed: inkjet, extrusion, and light-based 3D printers are nowadays available. Bioinks, i.e., the printing materials, also presented an evolution over the years. It seems that these new technologies might be extremely promising for bone regeneration. The purpose of the present review is to give a comprehensive summary of the past, the present, and future developments of bone bioprinting and bioinks, focusing the attention on crucial aspects of bone bioprinting such as selecting cell sources and attaining a viable vascularization within the newly printed bone. The main bioprinters currently available on the market and their characteristics have been taken into consideration, as well.

BMPR1A is necessary for chondrogenesis and osteogenesis, whereas BMPR1B prevents hypertrophic differentiation

BMP2 stimulates bone formation and signals preferably through BMP receptor (BMPR) 1A, whereas GDF5 is a cartilage inducer and signals preferably through BMPR1B. Consequently, BMPR1A and BMPR1B are believed to be involved in bone and cartilage formation, respectively. However, their function is not yet fully clarified. In this study, GDF5 mutants with a decreased affinity for BMPR1A were generated. These mutants, and wild-type GDF5 and BMP2, were tested for their ability to induce dimerization of BMPR1A or BMPR1B with BMPR2, and for their chondrogenic, hypertrophic and osteogenic properties in chondrocytes, in the multipotent mesenchymal precursor cell line C3H10T1/2 and the human osteosarcoma cell line Saos-2. Mutants with the lowest potency for inducing BMPR1A-BMPR2 dimerization exhibited minimal chondrogenic and osteogenic activities, indicating that BMPR1A is necessary for chondrogenic and osteogenic differentiation. BMP2, GDF5 and the GDF5 R399E mutant stimulated expression of chondrogenic and hypertrophy markers in C3H10T1/2 cells and chondrocytes. However, GDF5 R399E, which induces the dimerization of BMPR1B and BMPR2 more potently than GDF5 or BMP2, displayed reduced hypertrophic activity. Therefore, we postulate that stronger BMPR1B signaling, compared to BMPR1A signaling, prevents chondrocyte hypertrophy and acts as a cartilage stabilizer during joint morphogenesis.This article has an associated First Person interview with the first author of the paper.

Fibrin Glue/Fibronectin/Heparin-Based Delivery System of BMP2 Induces Osteogenesis in MC3T3-E1 Cells and Bone Formation in Rat Calvarial Critical-Sized Defects

Bone morphogenetic proteins (BMPs) have been used to promote bone formation in many clinical scenarios. However, the BMPs are inherently unstable in vivo and therefore need to be combined with carriers for controlled delivery. In this study, an innovative and efficient fibrin glue/fibronectin/heparin (FG/Fn/Hep)-based delivery system was developed for controlled release of BMP2. The incorporation of heparin can significantly slow the release of BMP2 without substantially affecting the structure and stiffness of the FG/Fn. The BMP2 release from the FG/Fn/Hep-BMP2 hydrogel is largely dominated by hydrogel degradation rather than simple diffusion. In vitro release experiments and MC3T3-E1 cell induction experiments showed that BMP2 can be released steadily and can induce MC3T3-E1 cells to differentiate into osteoblasts efficiently. This process is characterized by the significantly increased expression of calcium deposits, alkaline phosphatase, runt-related transcription factor-2, osteopontin, osteocalcin, and collagen I in comparison with the negative control. In vivo assessments revealed that the FG/Fn/Hep-BMP2 hydrogel significantly promotes bone regeneration in a rat calvarial critical-sized defect model. Our investigation indicates that FG/Fn/Hep-BMP2 hydrogel holds promise to be used as an alternative biomaterial for the repair of bone defects.

Therapeutic Applications of Genes and Gene-Engineered Mesenchymal Stem Cells for Femoral Head Necrosis

Osteonecrosis of the femoral head (ONFH) is a common and disabling joint disease. Although there is no clear consensus on the complex pathogenic mechanism of ONFH, trauma, abuse of glucocorticoids, and alcoholism are implicated in its etiology. The therapeutic strategies are still limited, and the clinical outcomes are not satisfactory. Mesenchymal stem cells (MSCs) have been shown to exert a positive impact on ONFH in preclinical experiments and clinical trials. The beneficial properties of MSCs are due, at least in part, to their ability to home to the injured tissue, secretion of paracrine signaling molecules, and multipotentiality. Nevertheless, the regenerative capacity of transplanted cells is impaired by the hostile environment of necrotic tissue in vivo, limiting their clinical efficacy. Recently, genetic engineering has been introduced as an attractive strategy to improve the regenerative properties of MSCs in the treatment of early-stage ONFH. This review summarizes the function of several genes used in the engineering of MSCs for the treatment of ONFH. Further, current challenges and future perspectives of genetic manipulation of MSCs are discussed. The notion of genetically engineered MSCs functioning as a "factory" that can produce a significant amount of multipotent and patient-specific therapeutic product is emphasized.

Femoral non-union above a fused knee: Successful treatment with exchange nailing and intramedullary delivery of bone morphogenetic protein

Bone healing is a complex and well-orchestrated physiological process, in which bone repairs and regenerates regaining its original biomechanical and biochemical properties. It is estimated that 5 to 10% of all fractures are complicated by delayed union or non-union. Progression to non-union is thought to be multifactorial, even though the exact biological sequence remains obscure. Treatment should aim to addressing deficiencies in both the mechanical and biological components, along with eliminating co-factors that could negatively affect the locally induced fracture healing response. We report a case of a 78-year-old patient who presented with a distal femoral non-union above a previously fused knee, which was successfully managed with exchange nailing and intramedullary delivery of recombinant human bone morphogenetic protein-7 (rhBMP-7).

rhBMP2 alone does not induce macrophage polarization towards an increased inflammatory response

Once thought to have revolutionized therapeutic intervention in surgery, Recombinant Human Bone Morphogenic Protein 2 (rhBMP2) is now in its second decade of sustained controversy over the side effects associated with its use. Side effects associated with clinical use of rhBMP2 (Infuse, Medtronic Inc) include a marked inflammatory response, pain, therapeutic failures, ectopic bone, tissue degradation, and death. What is missing, despite the depth of literature on the subject, is a direct interrogation of rhBMP2, specifically for inflammation. Here we set out to determine if rhBMP2 alters traditional macrophage markers associated with pro-inflammatory responses, and pro-reparative responses to injury. Based on our previous work, we hypothesized there would be no direct effect of the peptide on macrophage polarization. Here we utilized commercially available murine macrophages, RAW 264.7, and treated these cells with rhBMP2 in standard growth media or macrophage polarizing media (M1 and M2) at several doses of the peptide. Our readouts were cell viability, apoptosis, gene expression of M1 and M2 markers, and ELISA for M1 marker iNOS, and M2 marker Arg1. Our data give very little evidence to support an alteration in macrophage phenotype by rhBMP2 alone, or alteration of the phenotype when cultured in enriched M1 or M2 media. These results further suggest that other factors associated with the clinical use of Infuse, likely supraphysiological rhBMP2 doses and off label usage, are more likely the culprit for poor outcomes. This further reinforces the utility of rhBMP2 and other peptides in tissue engineering therapies when conditions are tightly controlled.

Comparative Efficacy of Commonly Available Human Bone Graft Substitutes as Tested for Posterolateral Fusion in an Athymic Rat Model

Background

Insufficient data exist on bone graft substitute materials efficacy; two thirds lack any clinical data.1,2 This prospective animal study identified efficacy differences among commercially available materials of several classes.

Methods

Historically validated muscle pouch osteoinduction study (OIS) and posterolateral fusion (PLF) were performed in an athymic rat model. Grafting material products implanted were demineralized bone matrix (DBM)-based allografts (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse, and Progenix Plus), allografts (OsteoSponge, MinerOss), cellular allograft (Osteocel Plus), ceramics (Mozaik Strip), or activated ceramics (Actifuse ABX Putty, Vitoss BA). After 4 weeks, OIS specimens were evaluated ex vivo by histologic osteoinductivity. After 8 weeks, PLF ex vivo specimens were evaluated for fusion by manual palpation (F_MP), radiography (F_XR), and histology (F_HISTO).

Results

OIS: No materials exhibited a rejection reaction on histology. All DBM-based materials exhibited osteoinductive potential as new bone formation at > 88% of implanted sites. One plain allograft (OsteoSponge) formed bone at 25% of sites. No bone formed for one ceramic (Mozaik Strip), three activated ceramics (Actifuse ABX Putty), or one cellular allograft, regardless of human bone marrow aspirate (hBMA) when added. PLF: Among the 10 DBMs, 6 had F_MP of 100% (Accell EVO3, DBX Mix, DBX Strip, Grafton Flex, Grafton Putty, Magnifuse), 2 had F_MP of 94% (Grafton Crunch, Grafton Matrix), and 2 conditions had F_MP of 0% (Progenix Plus, Progenix Plus + athymic rat iliac crest bone graft [arICBG]). Ceramics (Mozaik Strip), activated ceramics (Actifuse ABX Putty, Vitoss BA), plain allograft (OsteoSponge, MinerOss (PLF study), and cellular allograft (Osteocel Plus) demonstrated 0% F_MP. ArICBG demonstrated 13% F_MP.

Conclusions

Eight DBM-based materials (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse) demonstrated excellent (> 90% F_MP) efficacy in promoting fusion via bone healing. Two DBM conditions (Progenix Plus, Progenix Plus + arICBG) showed no manual palpation fusion (F_MP). Systematically, over the 2 studies (OIS and PLF), cellular (Osteocel Plus), plain allografts (OsteoSponge, MinerOss; PLF study), ceramic (Mozaik Strip), and activated ceramics (Actifuse ABX Putty, Vitoss BA) demonstrated poor F_MP efficacy (< 10%).

Clinical Relevance

When selecting DBMs, clinicians must be cognizant of variability in DBM efficacy by product and lot. While theoretically osteoinductive, cellular allograft and activated ceramics yielded poor in vivo efficacy. Whole allograft and ceramics may provide osteoconductive scaffolding for mixed-material grafting; however, surgeons should be cautious in using them alone. Direct clinical data are needed to establish efficacy for any bone graft substitute.

Indirect Bactericidal Properties of Recombinant Human Bone Morphogenetic Protein 2 In Vitro

PURPOSE

Bone morphogenetic proteins (BMPs) are secreted cytokines and are involved in various metabolic functions and inflammatory processes in different organs. The purpose of this study was to investigate whether BMPs also possess antimicrobial properties in direct or indirect ways.

MATERIALS AND METHODS

Antibacterial properties of recombinant human BMP2 (rhBMP2) were tested on 4 bacteria species (Staphylococcus aureus, Escherichia coli, Streptococcus mitis, Streptococcus constellatus) to examine the potential synergism of rhBMP2 with antibiotics. Indirect antibacterial properties were tested by infecting neutrophils with rhBMP2 and bacteria to investigate bacterial survival. Reactive oxidative species (ROS) production in neutrophils in the presence of rhBMP2 also was tested.

RESULTS

RhBMP2 in cardboard disks or sponge collagen as carriers did not show antibacterial activity against all tested bacteria. Further, synergism of rhBMP2 with antibiotics was not evident. Survival of bacteria inoculated with neutrophils and rhBMP2 led to a marked decrease in bacterial survival compared with neutrophils without rhBMP2. Although rhBMP2 inoculation of neutrophils alone did not induce ROS, its presence with the bacterial infection showed augmented ROS production for all tested bacteria.

CONCLUSIONS

RhBMP2 did not show direct antibacterial properties but did exhibit an indirect bactericidal effect in the presence of neutrophils. ROS production indicated that rhBMP2 has a role as a priming agent for neutrophils by augmenting their bactericidal capabilities and suggests the importance of its presence in contaminated surgical bone augmentation sites.

Sustained and Prolonged Delivery of Protein Therapeutics from Two-Dimensional Nanosilicates

We present a nanoengineered system for sustained and prolonged delivery of protein therapeutics, which has the potential to impact current orthopedic regeneration strategies. Specifically, we introduce two-dimensional nanosilicates with a high surface area and charged characteristics for delivery of active proteins for more than 30 days. The nanosilicates show high binding efficacy without altering the protein conformation and bioactivity. The released proteins are able to maintain high activity as demonstrated by enhanced differentiation of human mesenchymal stem cells at 10-fold lower concentration compared to the exogenous control. Utilizing the nanosilicates as a delivery vehicle could minimize the negative side effects observed because of the use of supraphysiological dosages of protein therapeutics for orthopedic regeneration strategies.

Tendon healing in the context of complex fractures

Tendons connect muscle to bone and play an integral role in bone and joint alignment and loading. Tendons act as pulleys that provide anchorage of muscle forces for joint motion and stability, as well as for fracture reduction and realignment. Patients that experience complex fractures also have concomitant soft tissue injuries, such as tendon damage or rupture. Tendon injuries that occur at the time of bone fracture have long-term ramifications on musculoskeletal health, yet these injuries are often disregarded in clinical treatment and diagnosis for patients with bone fractures as well as in basic science approaches for understanding bone repair processes. Delayed assessment of soft tissue injuries during evaluation of trauma can lead to chronic pain, dysfunction, and delayed bone healing even following successful fracture repair, highlighting the importance of identifying and treating damaged tendons early. Treatment strategies for bone repair, such as mechanical stabilization and biological therapeutics, can impact tendon healing and function. Because poor tendon healing following complex fracture can significantly impact the function of tendon during bone fracture healing, a need exists to understand the healing process of complex fractures more broadly, beyond the healing of bone. In this review, we explored the mechanical and biological interaction of bone and tendon in the context of complex fracture, as well as the relevance and potential ramifications of tendon damage following bone fracture, which has particular impact on patients that experience complex fractures, such as from combat, automobile accidents, and other trauma.

Nanogel Tectonics for Tissue Engineering: Protein Delivery Systems with Nanogel Chaperones

Amphiphilic polysaccharide self-assembled (SA) nanogels are promising protein carriers owing to their chaperone-like activity that allows them to nanoencapsulate proteins within their polymer networks. The chaperoning function is an important concept that has led to breakthroughs in the development of effective protein drug delivery systems by stabilizing formulations and controlling the quality of unstable proteins. Recently, nanogel-tectonic materials that integrate SA nanogels as building blocks have been designed as new hydrogel biomaterials. This article describes recent progress and applications of SA nanogel tectonic materials as protein delivery systems for tissue engineering.

Improvement of calcium phosphate scaffold osteogenesis in vitro via combination of glutamate-modified BMP-2 peptides

Alpha-tricalcium phosphate (α-TCP) based porous scaffolds have superior osteoconduction and osteoinduction in bone tissue engineering, furthermore, these 3D porous scaffolds can be used as efficient drug delivery carriers. In the concept of tissue engineering, the "drugs" could be defined as drug molecules or biomacromolecules, even cells. These "drugs" have endowed the scaffolds which were laden improved abilities compared with the blank scaffolds. In this study, we anchored osteogenic bone morphogenetic protein-2 (BMP-2) derived peptides to α-TCP 3D porous scaffolds by linking the E7 domain to the target peptides, constructed the modified active peptides (E7BMP-2 peptides) delivery system, which finally achieved the modified peptides sustaining release and enhanced rat bone marrow mesenchymal stem cells (BMSCs) osteogenic differentiation in vitro. The α-TCP 3D porous scaffolds had micropores and interconnected micropores which expanded surface area of the scaffolds. The release test testified the constructed the delivery system had realized long-term release in which the peptides dosage could be detected by the BCA protein assay kit after 10 days compared with BMP-2 proteins which absorbed on the same α-TCP 3D porous scaffolds. The constructed E7BMP-2 peptides delivery system supported rat BMSCs osteogenic differentiation in the form of improving the genes expression levels of Runx2, ALP and OCN. Based on electrostatic interactions, E7 domain fastened combination between the active BMP-2 derived peptides and the α-TCP 3D porous scaffolds, the sustaining E7BMP-2 peptides release promoted the BMSCs osteogenesis as BMP-2 proteins did, which endowed α-TCP 3D porous scaffolds enhanced osteoinductive abilities in vitro.

Induced membrane technique for the treatment of severe acute tibial bone loss: preliminary experience at medium-term follow-up

PURPOSE

Management of acute open tibial fractures with critical bone defect remains a challenge in trauma surgery. Few and heterogeneous cases have been reported about the treatment with the induced membrane technique.

METHODS

We prospectively evaluated three patients treated with the induced membrane technique for acute Gustilo IIIB tibial fractures with critical bone defect. Success treatment was defined by bone union with patient pain free. Clinical and radiological evaluations were performed regularly until healing, then annually and with a minimum follow-up of five years.

RESULTS

In all patients but one, a success was recorded, respectively, at four and six months. These two patients were pain free until the final follow-up, and no graft resorption or secondary complications related to the index surgery were observed. The third case was managed successfully with a bone transport technique.

CONCLUSION

The induced membrane technique is an alternative good option for the treatment of these severe lesions.

Escherichia coli-derived BMP-2-absorbed β-TCP granules induce bone regeneration in rabbit critical-sized femoral segmental defects

PURPOSE

This study investigated whether Escherichia coli-derived bone morphogenetic protein (BMP)-2 (E-BMP-2) adsorbed onto β-tricalcium phosphate (β-TCP) granules can induce bone regeneration in critical-size femoral segmental defects in rabbits.

METHODS

Bone defects 20 mm in size and stabilized with an external fixator were created in the femur of New Zealand white rabbits, which were divided into BMP-2 and control groups. E-BMP-2-loaded β-TCP granules were implanted into defects of the BMP-2 group, whereas defects in the controls were implanted with β-TCP granules alone. At 12 and 24 weeks after surgery, radiographs were obtained of the femurs and histological and biomechanical assessments of the defect area were performed. Bone regeneration was quantified using micro-computed tomography at 24 weeks.

RESULTS

Radiographic and histologic analyses revealed bone regeneration in the BMP-2 group but not the control group; no fracturing of newly formed bone occurred when the external fixator was removed at 12 weeks. At 24 weeks, tissue mineral density, the ratio of bone volume to total volume, and volumetric bone mineral density of the callus were higher in the BMP-2 group than in control animals. In the former, ultimate stress, extrinsic stiffness, and failure energy measurements for the femurs were higher at 24 weeks than at 12 weeks.

CONCLUSION

E-BMP-2-loaded β-TCP granules can effectively promote bone regeneration in long bone defects.

Pigs are useful for the molecular study of bone inflammation and regeneration in humans

Pigs are used with increased frequency to model different kinds of orthopedic surgical conditions. In order to show the full potential of porcine models in orthopedic research, it is therefore required to examine the expression of bone regulatory genes in pigs affected by orthopedic surgery and compare it to the expression in humans and mice as mice, are one of the most applied animal species in orthopedics today. In the present study, the local molecular response to drilling of a tibial implant cavity, and the subsequent insertion of a steel implant was examined in a porcine model. Pigs were euthanized five days after drilling of the bone. The molecular response of 73 different genes was analyzed using a high-throughput quantitative polymerase chain reaction platform and compared to histopathology. Histologically, it was found that bone remodeling was initiated on day 5 after surgery and was associated with upregulation of several genes involved in bone degradation and formation ( CTSK, ACP5, IBSP, RANK, RANKL and COL1A1). Interleukin-6 and several acute-phase proteins (C3, SAA and ITIH4) were significantly upregulated, indicating their importance in the initial process of healing and osseointegration. All tested bone morphogenic proteins (BMP2, -4 and -7) including their inhibitor noggin were also significantly upregulated. Surprisingly, vascular endothelial growth factor A was not found to be regulated five days after surgery while several other vascular growth factors (ANGPT1, ANGPT2 and PTN) were upregulated. The pig was found to be a useful model for elucidation of bone regulatory genes in humans.

Treatment of an atrophic clavicle non-union with the chamber induction technique: a case report

The gold standard technique for treating non-union of the clavicle is based on corticocancellous bone graft harvested from the iliac crest and fixation with a plate. In cases of large clavicular defects, this surgical procedure becomes ineffective and only a complex bone reconstruction can be considered. In the herein study we report on a clavicular non-union which was associated with a 4cm bone defect that was managed successfully with optimum fixation and the Chamber Induction Technique (C.I.T)-formation of the masquelet membrane- and subsequent biological augmentation with a composite bone graft.

Long-term outcome following additional rhBMP-7 application in revision surgery of aseptic humeral, femoral, and tibial shaft nonunion

Background

Surgical revision concepts for the treatment of aseptic humeral, femoral, and tibial diaphyseal nonunion were evaluated. It was analyzed if the range of time to bone healing was shorter, and if clinical and radiological long-term outcome was better following application of additional recombinant human Bone Morphogenetic Protein-7 (rhBMP-7) compared to no additional rhBMP-7 use.

Methods

In a retrospective comparative study between 06/2006 and 05/2013, 112 patients diagnosed with aseptic diaphyseal humerus (22 patients), femur (41 patients), and tibia (49 patients) nonunion were treated using internal fixation and bone graft augmentation. For additional stimulation of bone healing, growth factor rhBMP-7 was locally administered in 62 out of 112 patients. Follow-up studies including clinical and radiological assessment were performed at regular intervals as well as after at least one year following nonunion surgery.

Results

One hundred and two out of 112 (humerus: 19, femur: 37, tibia: 47) nonunion healed within 12 months after revision surgery without any significant differences between the cohort groups. According to the DASH outcome measure for the humerus (p = 0.679), LEFS for the femur (p = 0.251) and the tibia (p = 0.946) as well as to the SF-12 for all entities, no significant differences between the treatment groups were found.

Conclusions

Aseptic diaphyseal nonunion in humerus, femur, and tibia healed irrespectively of additional rhBMP-7 application. Moreover, the results of this study suggest that successful nonunion healing can be linked to precise surgical concepts using radical removal of nonunion tissue, stable fixation and restoration of axis, length and torsion, rather than to the additional use of signaling proteins.

Trial registration

This clinical trial was conducted according to ICMJE guidelines as well as to the approval of the National Medical Board (Ethics Committee of the Bavarian State Chamber of Physicians; TRN: 2016-104) and has been retrospectively registered with the German Clinical Trails Register (TRN: DRKS00012652).

Physicochemical and biological characteristics of BMP-2/IGF-1-loaded three-dimensional coaxial electrospun fibrous membranes for bone defect repair

Coaxial electrospun fibrous membranes show favorable mechanical properties for use in guided bone regeneration (GBR). We used coaxial electrospinning technology to fabricate three-dimensional nanofiber membranes loaded with BMP-2 and IGF-1, and assessed the physicochemical and biological properties of these novel membranes in vitro. We fabricated four experimental groups of BMP-2/IGF-1/BSA-loaded membranes with different flow ratios (shell/core). Membrane characteristics were assessed by scanning and transmission electron microscopy, and laser confocal microscopy. Physicochemical and drug release properties were evaluated based on contact angle, mechanical property testing, X-ray diffraction analysis, and ELISA. The membranes were seeded with bone marrow-derived mesenchymal stem cells (BMMSCs) to estimate their biological properties based on cell viability and alkaline phosphatase (ALP) activity. The four membrane groups presented uniform diameters and core-shell structures. Acceleration of the shell solution flow rate increased the contact angle and mechanical properties of the fibrous membrane, while dual-factor addition did not impact fiber structure. Each drug-loaded membrane showed a gradually increasing release curve, with varying degrees of burst and sustained release. Compared to the other groups, the membranes with a core-shell flow ratio of 1:10 showed better drug-loading capacity and sustained release performance, higher biological properties and good barrier function. Optimal parameters were chosen based on the physical and chemical characteristics and biological properties of the membrane. Our results imply that the BMP-2/IGF-1/BSA-loaded coaxial electrospun fibrous membrane with optimum parameters is a suitable barrier membrane for GBR, and releases multiple factors promoting osteoconduction and osteoinduction.

Genetic and pharmacological inhibition of retinoic acid receptor γ function promotes endochondral bone formation

The nuclear retinoic acid receptors (RARs) play key roles in skeletal development and endochondral ossification. Previously, we showed that RARγ regulates chondrogenesis and that pharmacological activation of RARγ blocked heterotopic ossification (HO), pathology in which endochondral bone forms in soft tissues. Thus, we reasoned that pharmacological inhibition of RARγ should enhance endochondral ossification, leading to a potential therapeutic strategy for bone deficiencies. We created surgical bone defects in wild type and RARγ-null mice and monitored bone healing. Fibrous, cartilaginous, and osseous tissues formed in both groups by day 7, but more cartilaginous tissue formed in mutants within and around the defects compared to controls. Next, we implanted a mixture of Matrigel and rhBMP2 subdermally to induce ectopic endochondral ossification. Administration of RARγ antagonists significantly stimulated ectopic bone formation in wild type but not in RARγ-null mice. The antagonist-induced increases in bone formation were preceded by increases in cartilage formation and were accompanied by higher levels of phosphorylated Smad1/5/8 (pSmad1/5/8) compared to vehicle-treated control. Higher pSmad1/5/8 levels were also observed in cartilaginous tissues forming in healing bone defects in RARγ-null mice, and increases in pSmad1/5/8 levels and Id1-luc activity were observed in RARγ antagonist-treated chondrogenic cells in culture. Our data show that genetic or pharmacological interference with RARγ stimulates endochondral bone formation and does so at least in part by stimulating canonical BMP signaling. This pharmacologic strategy could represent a new tool to enhance endochondral bone formation in the setting of various orthopedic surgical interventions and other skeletal deficiencies. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1096-1105, 2017.

Clinical application of bone morphogenetic proteins for bone healing: a systematic review

PURPOSE

This paper documents the existing evidence on bone morphogenetic proteins (BMPs) use for the treatment of bone fractures, non-union, and osteonecrosis, through a review of the clinical literature, underlying potential and limitations in terms of cost effectiveness and risk of complications.

METHODS

A systematic review was performed on the PubMed database using the following string: (bone morphogenetic proteins OR BMPs) and (bone repair OR bone regeneration) including papers from 2000 to 2016. The search focused on clinical trials dealing with BMPs application to favor bone regeneration in bone fractures, non-union, and osteonecrosis, in English language, with level of evidence I, II, III, and IV. Relevant data (type of study, number of patients, BMPs delivery material, dose, site, follow-up, outcome, and adverse events) were extracted and analyzed.

RESULTS

Forty-four articles met the inclusion criteria: 10 randomized controlled trials (RCTs), 7 comparative studies, 18 case series, and 9 case reports. rhBMP-2 was documented mainly for the treatment of fractures, and rhBMP-7 mainly for non-unions and osteonecrosis. Mixed results were found among RCTs and comparative papers: 11 reported positive results for BMPs augmentation, 3 obtained no significant effects, and 2 showed negative results. The only study comparing the two BMPs showed a better outcome with rhBMP-2 for non-union treatment.

CONCLUSION

Clinical evidence on BMPs use for the treatment of fractures, non-union, and osteonecrosis is still controversial, with the few available reports being mainly of low quality. While positive findings have been described in many studies, mixed results are still present in the literature in terms of efficacy and adverse events. The difficulties in drawing clear conclusions are also due to the studies heterogeneity, mainly in terms of different BMPs applied, with different concomitant treatments for each bone pathology. Therefore, further research with well-designed studies is needed in order to understand the real potential of this biological approach to favour bone healing.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for the prediction of non-union consolidation

INTRODUCTION

Non-union perfusion can be visualized with dynamic contrast-enhanced (DCE) MRI. This study evaluated DCE-MRI to predict non-union consolidation after surgery and detect factors that affect bone healing.

MATERIALS AND METHODS

Between 2010 and 2015 non-union perfusion was prospectively quantified in 205 patients (mean age, 51.5 years, 129 men, 76 women) before intervention and at 6, 12, 26, 52 and more weeks follow-up. DCE-MRI results were related to the osseous consolidation, the ability to predict successful outcome was estimated by ROC analysis. The relevance of the body mass index (BMI) and the non-union severity score (NUSS) to the healing process was assessed.

RESULTS

Tibial (n=99) and femoral (n=76) non-unions were most common. Consolidation could be assessed in 169 patients, of these 103 (61%) showed eventual healing and demonstrated higher perfusion than in failed consolidation at 6 (p=0.0226), 12 (p=0.0252) and 26 (p=0.0088) weeks follow-up. DCE-MRI at 26 weeks follow-up predicted non-union consolidation with a sensitivity of 75% and a specificity of 87% (false classification rate 19%). Higher BMI (p=0.041) and NUSS (p<0.0001) were associated with treatment failure.

CONCLUSIONS

DCE-MRI perfusion analysis after non-union surgery predicts successful outcome and could facilitate the decision of early intervention. NUSS and BMI are important prognostic factors concerning consolidation.

Limb reconstruction after traumatic bone loss

A variety of options exist to reconstruct limbs following traumatic bone loss. The management of these injuries is challenging and often requires prolonged and potentially painful treatment. The Ilizarov technique of bone transport using circular external fixators is widely used for limb reconstruction of large bone defects. Other techniques include vascularised fibular grafting, the use of induced pseudosynovial membranes combined with cancellous autologous bone grafts and the use of autologous, allogeneic or synthetic bone grafts on their own for smaller defects. Future directions include further research on bone tissue engineering using stem cell therapy and growth factors such as bone morphogenetic proteins. The purpose of this Continuing Medical Education article is to describe the key limb reconstructive techniques that may be employed to treat traumatic bone loss. In particular, this article is intended to serve as a revision tool for those preparing for postgraduate examinations.

Osteogenic Differentiation Capacity of In Vitro Cultured Human Skeletal Muscle for Expedited Bone Tissue Engineering

Expedited bone tissue engineering employs the biological stimuli to harness the intrinsic regenerative potential of skeletal muscle to trigger the reparative process in situ to improve or replace biological functions. When genetically modified with adenovirus mediated BMP2 gene transfer, muscle biopsies from animals have demonstrated success in regenerating bone within rat bony defects. However, it is uncertain whether the human adult skeletal muscle displays an osteogenic potential in vitro when a suitable biological trigger is applied. In present study, human skeletal muscle cultured in a standard osteogenic medium supplemented with dexamethasone demonstrated significant increase in alkaline phosphatase activity approximately 24-fold over control at 2-week time point. More interestingly, measurement of mRNA levels revealed the dramatic results for osteoblast transcripts of alkaline phosphatase, bone sialoproteins, transcription factor CBFA1, collagen type I, and osteocalcin. Calcified mineral deposits were demonstrated on superficial layers of muscle discs after an extended 8-week osteogenic induction. Taken together, these are the first data supporting human skeletal muscle tissue as a promising potential target for expedited bone regeneration, which of the technologies is a valuable method for tissue repair, being not only effective but also inexpensive and clinically expeditious.

Interaction between living bone particles and rhBMP-2 in large segmental defect healing in the rat femur

Orthopedic surgeons sometimes combine recombinant, human BMP-2 with autograft bone when dealing with problematic osseous fractures. Although some case reports indicate success with this off-label strategy, there have been no randomized controlled trials. Moreover, a literature search revealed only one pre-clinical study and this was in a cranial defect model. The present project examined the consequences of combining BMP-2 with particles of living bone in a rat femoral defect model. Human bone particles were recovered with a reamer-irrigator-aspirator (RIA). To allow acceptance of the xenograft as surrogate autograft, rats were administered an immunosuppressive cocktail that does not interfere with bone healing. Implantation of 200 µg living bone particles generated a small amount of new bone and defects did not heal. Graded amounts of BMP-2 that alone provoked no healing (1.1 µg), borderline healing (5.5 µg), or full healing (11 µg) were added to this amount of bone particles. Addition of BMP-2 (1.1 µg) increased osteogenesis, and produced bridging in 2 of 7 defects. The combination of BMP-2 (5.5 µg) and bone particles made healing more reliable and advanced the maturation of the regenerate. Bone formation with BMP-2 (11 µg) and bone particles showed improved maturation. Thus, the combination of autograft and BMP-2 may be helpful clinically under conditions where the healing response is suboptimal. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2137-2145, 2016. Clinical significance These data support the clinical use of recombinant, human BMP-2 with autograft bone when treating large segmental osseous defects. The combination leads to greater bone formation and accelerates the maturation of the regenerate.

Treatment of recalcitrant atrophic non-union of the humeral shaft with BMP-7, autologous bone graft and hydroxyapatite pellets

Recalcitrant humeral non-union is a disabling condition that is extremely difficult to treat. The use of BMP-7 has been proposed to improve bone healing. This is a report of the results obtained in 12 patients with recalcitrant humeral non-union treated using stable fixation with a long locking compression plate and BMP-7, autologous bone graft and hydroxyapatite pellets applied at the non-union site. Patients had up to three surgical attempts at non-union healing prior to our treatment. The average time from the initial fracture to our surgery was 5.2 years. Average follow-up was 5.3 years. At follow-up, non-union had healed in all patients by an average of 7.3 months. All the patients were very satisfied with their final results, despite a restricted range of motion of the elbow and a moderate muscular atrophy, which was frequently observed. Our study shows that BMP-7 associated with autologous bone grafting and hydroxyapatite pellets after stable fixation is an effective adjuvant to stimulate bone healing in the treatment of recalcitrant humeral non-union.

The role of peptides in bone healing and regeneration: a systematic review

BACKGROUND

Bone tissue engineering and the research surrounding peptides has expanded significantly over the last few decades. Several peptides have been shown to support and stimulate the bone healing response and have been proposed as therapeutic vehicles for clinical use. The aim of this comprehensive review is to present the clinical and experimental studies analysing the potential role of peptides for bone healing and bone regeneration.

METHODS

A systematic review according to PRISMA guidelines was conducted. Articles presenting peptides capable of exerting an upregulatory effect on osteoprogenitor cells and bone healing were included in the study.

RESULTS

Based on the available literature, a significant amount of experimental in vitro and in vivo evidence exists. Several peptides were found to upregulate the bone healing response in experimental models and could act as potential candidates for future clinical applications. However, from the available peptides that reached the level of clinical trials, the presented results are limited.

CONCLUSION

Further research is desirable to shed more light into the processes governing the osteoprogenitor cellular responses. With further advances in the field of biomimetic materials and scaffolds, new treatment modalities for bone repair will emerge.

The missing effect of human recombinant Bone Morphogenetic Proteins BMP-2 and BMP-7 in surgical treatment of aseptic forearm nonunion

INTRODUCTION

In this cohort study, the surgical revision concept of open compression plating and autologous bone grafting with and without additional application of BMP for treatment of aseptic ulna and/or radius shaft nonunion was evaluated. The purpose was to evaluate the clinical and radiological outcome, and to determine any difference in osseous healing, range of time between revision surgery and bone healing, and postoperative complications between the cohort groups.

PATIENTS AND METHODS

Between 01/2005 and 03/2015, a prospective, randomised, controlled cohort study was performed in a Level I Trauma Centre. Forty-nine patients were treated with the diagnosis of aseptic diaphyseal ulnar and/or radial shaft nonunion using compression plating and autologous bone grafting. Additional biological augmentation using BMP-2 or BMP-7 was performed in 24 patients. Clinical and radiological follow-up was performed six weeks, three and six months after revision surgery in accordance to the system by Anderson.

RESULTS

The study group consisted of 38 men and 11 women with a median age of 44 years (range 19-77). Twenty-four out of 49 patients obtained compression plating either with autologous iliac crest bone grafting (11/24 patients) or cancellous bone grafting (13/24 patients) and additional application of BMP-2 (4/24 patients) or BMP-7 (20/24 patients). The remaining 25 patients did not receive any additional application of BMP, but autologous bone grafting. The median follow-up was 15 months (range 6-54 months). Forty-six out of 49 nonunion healed within 12 months after revision surgery with a median time to union of six months. The clinical outcome, as assessed using the system by Anderson, as well as osseous healing, duration of time interval between revision surgery and bone healing, and postoperative complications did not demonstrate significant differences between the cohort groups.

DISCUSSION

Atrophic/oligotrophic forearm nonunion healed irrespective of additional application of BMP combined with autologous bone grafting. For successful treatment, radical resection of fibrous nonunion tissue and internal compression plate fixation is required with the aim of achieving high degree of rigid stability. Also, correction of angular deformities, restoration of length, and precise axial alignment of the distal radio-ulnar joint are mandatory prerequisites to successfully achieve bone healing.

Repair of a Complicated Calvarial Defect: Reconstruction of an Infected Wound With rhBMP-2

BACKGROUND

Management of the previously infected craniofacial defect remains a significant clinical challenge, posing obstacles such as wound healing complications, lack of donor site availability, and predisposition to failure of the repair. Optimal therapy would reconstruct like with like, without donor site morbidity. The purpose of this study was to compare the efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2)-mediated bone regeneration with the current standard of autologous bone graft for repair of previously infected calvarial defects.

METHODS

Nineteen adult New Zealand white rabbits underwent subtotal calvariectomy. Bone flaps were inoculated with Staphylococcus aureus and replanted. After 1 week of infection, bone flaps were removed, and wounds were debrided, followed by 10 days of antibiotic treatment. After 6 weeks, animals underwent scar debridement followed by definitive reconstruction in 1 of 4 groups: empty control (n = 3), vehicle control (buffer solution on absorbable collagen sponge [ACS], n = 3), autologous bone graft (n = 3), or rhBMP-2 repair (rhBMP-2/ACS, n = 10). Animals underwent computed tomography imaging at 0, 2, 4, and 6 weeks postoperatively, followed by euthanization and histological analysis. Percent healing was determined by 3-dimensional analysis. A (time × group) 2-way analysis of variance was performed on healing versus treatment group and postoperative time.

RESULTS

At 6 weeks postoperatively, rhBMP-2/ACS and autologous bone graft resulted in 93% and 68% healing, respectively, whereas the empty and vehicle control treatment resulted in 27% and 26% healing (P < 0.001). Histologically, compared to autologous bone graft, bone in the rhBMP-2/ACS group was more cellular and more consistently continuous with wound margins.

CONCLUSIONS

The rhBMP-2 therapy is effective in achieving radiographic coverage of previously infected calvarial defects.

Bone printing: new frontiers in the treatment of bone defects

Bone defects can be congenital or acquired resulting from trauma, infection, neoplasm and failed arthroplasty. The osseous reconstruction of these defects is challenging. Unfortunately, none of the current techniques for the repair of bone defects has proven to be fully satisfactory. Bone tissue engineering (BTE) is the field of regenerative medicine (RM) that focuses on alternative treatment options for bone defects that will ideally address all the issues of the traditional techniques in treating large bone defects. However, current techniques of BTE is laborious and have their own shortcomings. More recently, 2D and 3D bone printing has been introduced to overcome most of the limitations of bone grafts and BTE. So far, results are extremely promising, setting new frontiers in the management of bone defects.

Long bone non-unions treated with the diamond concept: a case series of 64 patients

The aim of this retrospective study with prospectively documented data was to report the clinical results of treatment of long bone non-unions using the "diamond concept". Over a 4-year period, patients that presented with a long bone non-union and were managed with the diamond conceptual framework of bone repair were evaluated. Exclusion criteria were hypertrophic, pathological, and infected non-unions. Fixation was revised as it was indicated whilst biological enhancement included the implantation of RIA graft, BMP-7 and concentrated bone marrow aspirate. Data recorded included patient demographics, initial fracture pattern and type of stabilisation, number of previous interventions, time to reoperation, time to union and functional outcome. Painless full weight bearing defined clinical union. Radiological union was defined as the presence of mature callous bridging to at least 3 bone cortices. The minimum follow up was 12 months (range 12-32). In total 64 patients (34 males) with a mean age of 45 years (17-83) were evaluated. Anatomical distribution of non-unions included the femur (54.68%), tibia (34.38%), humerus (4.68%), radius (3.13%) and clavicle (3.13%). The median number of previous interventions was 1 (range 1-5). The majority of patients (82.62%) underwent revision of fixation whereas only bone grafting was performed 9.38% of patients. Three patients developed superficial wound infection (one was MRSA), 1 had deep vein thrombosis and 1 developed heterotopic bone formation. Union was successful in 63/64 (98.4%) non-unions at a mean time of 6 months (range 3-12). All patients were mobilising pain free and returned to their daily living activities at the final follow up. The application of the "diamond concept" in this cohort of patients was associated with a high union rate by providing an optimal mechanical and biological environment. Such an approach should be considered in the surgeon's armamentarium particularly in such cases where difficulty of bone repair is foreseen.

Clinical effectiveness of Osigraft in long-bones non-unions

Current evidence, based primarily on case series, suggest that the eptotermin alfa (recombinant bone morphogenetic protein-7 (rhBM-7)), which is commercialized as Osigraft with an indication for tibial non-union, used in monotherapy or polytherapy, is a safe and effective therapy for long bones non-unions of lower and upper limbs. No previous study has compared the safety and the efficacy of Osigraft and the "gold standard" treatment for recalcitrant long-bones non-union, autologous bone graft (ABG). This study aims to compare the effectiveness of Osigraft and ABG in the treatment of post-traumatic, persistent long bone non-unions. In particular, the present study will focus exclusively on complex persistent non-unions, excluding simpler cases, in which it is likely that a simple revision of the osteosynthesis will be sufficient to promote union, and extremely severe cases in which there is an indication for amputation and prosthesis. The study addresses the following research question: 1. Is the effectiveness of eptotermin alfa comparable to that of ABG in the treatment of complex long bone non-unions? 2. Are there significant differences in the prevalence of adverse events between patients treated with eptotermin alfa and those treated with ABG? The study is an observational, retrospective study, located in one Experimental Recruiting Center (Ospedale Universitario G. PINI - Milano). The study was conducted with ethics approval and according with the existing Italian law. Demographic and clinical data were collected from patients Clinical Medical Records and other existing documentation, through a web based eCRF. The treatment (surgery with Osigraft or ABG) effectiveness was evaluated comparing the number of success cases (primary endpoint) and the length for clinical and radiological healing (secondary end-points). The treatment safety was evaluating comparing the prevalence of Adverse Events. Osigraft was demonstrated to be statistically equivalent to ABG with respect to the primary and secondary end point of surgical success. The treatment success was statistically comparable across all the anatomical regions considered, both in patients treated with Osigraft and in patients treated with ABG. The use of Osigraft when compared to autograft was associated with statistically lower intraoperative blood loss and shorter operative times. In addition patients treated with Osigraft developed statistically less peri-operative and late onset adverse events, compared to ABG. The difference was substantially due to the occurrence of pain at donor site in patients treated with ABG.

Management of a humeral shaft non-union after a Gustilo III C fracture

A 25-year-old man was admitted to our Department with an open humeral shaft fracture (Gustilo III C); two large wounds were noticed with ulnar artery and median nerve completely dissected. Initial primary treatment included irrigation, debridement and fracture stabilization with a monolateral external fixator followed by vascular and nerve repair and wound closure. At 6 months follow up the patient was able to use his arm without any painful stimuli and a CT scan showed the presence of postero-medial callus formation. Consequently, the external fixator was removed and the patient was discharged to physiotherapy. After 7 months, the patient presented with severe pain and functional impairment with no history of trauma. X rays showed recent re-fracture on a background of oligotrophic nonunion. Revision surgery included debridement of the non-union bone edges, reaming of the medullary canal and insertion of a humeral nail. Six months later osseous healing was noted with complete restoration of shoulder and elbow movement and partial recovery of the median nerve.