Establishment and characterization of the Masquelet induced membrane technique in a rat femur critical-sized defect model

Knowledge mapping of induced membrane technique: a scientometric study from 2004 to 2023

BACKGROUND

The induced membrane technique (IMT) is a two-step procedure used for reconstructing segmental bone defects in the limbs. The osteogenic mechanism after bone grafting using IMT remains unclear, and efforts to modify the original techniques are limited to the investigative phase. Therefore, reviewing existing knowledge and identifying hotspots and new trends in IMT is critical.

METHODS

We retrieved reviews and articles associated with IMT published between 2004 and 2023 from the Web of Science Core Collection (WoSCC). The keywords included induced membrane technique, guided bone regeneration, bone defect reconstruction, bone graft, stem cells, Masquelet technique, management of bone defects, and scaffold. HistCite, VOSviewer, CiteSpace, and R-bibliometrics were used for scientometric analysis.

RESULTS

A total of 1019 publications from 374 academic journals with 33,995 co-cited references by 2,331 institutions from 65 countries or regions were included. China (n = 235) and the United States (n = 215) were the most productive countries, with Shanghai Jiao Tong University producing the most number of publications (n = 18). Journal Injury [co-citations = 1774; impact factor (IF) 2022 = 2.5] published the most manuscripts, while Masquelet AC and Giannoudis PV published literature with a significant influence on IMT, showing more co-citations (n = 727; n = 355). Two preface hotspots of IMT focused on investigating the microscopic mechanism (such as the membrane supporting graft-to-bone union and the role of inflammatory cells) and developing new techniques to improve IMT (such as bone tissue engineering and new drugs).

CONCLUSION

This study comprehensively reviewed the literature about IMT published in the last 20 years using qualitative and quantitative methods, providing valuable information for researchers investigating IMT.

Modified and alternative bone cements can improve the induced membrane: Critical size bone defect model in rat femur

BACKGROUND

As a two-stage surgical procedure, Masquelet's technique has been used to care for critical-size bone defects (CSD). We aimed to determine the effects of modified and altered bone cement with biological or chemical enriching agents on the progression of Masquelet's induced membrane (IM) applied to a rat femur CSD model, and to compare the histopathological, biochemical, and immunohistochemical findings of these cements to enhance IM capacity.

METHODS

Thirty-five male rats were included in five groups: plain polymethyl methacrylate (PMMA), estrogen-impregnated PMMA (E+PMMA), bone chip added PMMA (BC+PMMA), hydroxyapatite-coated PMMA (HA) and calcium phosphate cement (CPC). The levels of bone alkaline phosphatase (BALP), osteocalcin (OC), and tumor necrosis factor-alpha (TNF-α) were analyzed in intracardiac blood samples collected at the end of 4 weeks of the right femur CSD intervention. All IMs collected were fixed and prepared for histopathological scoring. The tissue levels of rat-specific Transforming Growth Factor-Beta (TGF-β), Runt-related Transcription Factor 2 (Runx2), and Vascular Endothelial Growth Factor (VEGF) were analyzed immunohistochemically.

RESULTS

Serum levels of BALP and OC were significantly higher in E+PMMA and BC+PMMA groups than those of other groups (P = 0.0061 and 0.0019, respectively). In contrast, TNF-α levels of all groups with alternative bone cement significantly decreased compared to bare PMMA (P = 0.0116). Histopathological scores of E+PMMA, BC+PMMA, and CPC groups were 6.86 ± 1.57, 4.71 ± 0.76, and 6.57 ± 1.51, respectively, which were considerably higher than those of PMMA and HA groups (3.14 ± 0.70 and 1.86 ± 0.69, respectively) (P < 0.0001). Significant increases in TGF-β and VEGF expressions were observed in E+PMMA and CPC groups (P = 0.0001 and <0.0001, respectively) whereas Runx2 expression significantly increased only in the HA group compared to other groups (P < 0.0001).

CONCLUSIONS

The modified PMMA with E and BC, and CPC as an alternative spacer resulted in a well-differentiated IM and increased IM progression by elevating BALP and OC levels in serum and by mediating expressions of TGF-β and VEGF at the tissue level. Estrogen-supplemented cement spacer has yielded promising findings between modified and alternative bone cement.

Human Acellular Collagen Matrices-Clinical Opportunities in Tissue Replacement

The field of regenerative medicine is increasingly in need of effective and biocompatible materials for tissue engineering. Human acellular dermal matrix (hADM)-derived collagen matrices stand out as a particularly promising candidate. Their ability to preserve structural integrity, coupled with exceptional biocompatibility, positions them as a viable choice for tissue replacement. However, their clinical application has been largely confined to serving as scaffolds. This study aims to expand the horizon of clinical uses for collagen sheets by exploring the diverse cutting-edge clinical demands. This review illustrates the clinical utilizations of collagen sheets beyond traditional roles, such as covering skin defects or acting solely as scaffolds. In particular, the potential of Epiflex®, a commercially available and immediately clinically usable allogeneic membrane, will be evaluated. Collagen sheets have demonstrated efficacy in bone reconstruction, where they can substitute the induced Masquelet membrane in a single-stage procedure, proving to be clinically effective and safe. The application of these membranes allow the reconstruction of substantial tissue defects, without requiring extensive plastic reconstructive surgery. Additionally, they are found to be apt for addressing osteochondritis dissecans lesions and for ligament reconstruction in the carpus. The compelling clinical examples showcased in this study affirm that the applications of human ADM extend significantly beyond its initial use for skin defect treatments. hADM has proven to be highly successful and well-tolerated in managing various etiologies of bone and soft tissue defects, enhancing patient care outcomes. In particular, the application from the shelf reduces the need for additional surgery or donor site defects.

The Masquelet induced membrane technique with PRP-FG-nHA/PA66 scaffold can heal a rat large femoral bone defect

BACKGROUND

Masquelet membrane induction technology is one of the treatment strategies for large bone defect (LBD). However, the angiogenesis ability of induced membrane decreases with time and autologous bone grafting is associated with donor site morbidity. This study investigates if the PRP-FG-nHA/PA66 scaffold can be used as a spacer instead of PMMA to improve the angiogenesis ability of induced membrane and reduce the amount of autologous bone graft.

METHODS

Platelet rich plasma (PRP) was prepared and PRP-FG-nHA/PA66 scaffold was synthesized and observed. The sustained release of VEGFA and porosity of the scaffold were analyzed. We established a femur LBD model in male SD rats. 55 rats were randomly divided into four groups depending on the spacer filled in the defect area. "Defect only" group (n = 10), "PMMA" group (n = 15), "PRP-nHA/PA66" group (n = 15) and "PRP-FG-nHA/PA66" group (n = 15 ). At 6 weeks, the spacers were removed and the defects were grafted. The induced membrane and bone were collected and stained. The bone formation was detected by micro-CT and the callus union was scored on a three point system.

RESULTS

The PRP-FG-nHA/PA66 scaffold was porosity and could maintain a high concentration of VEGFA after 30 days of preparation. The induced membrane in PRP-FG-nHA/PA66 group was thinner than PMMA, but the vessel density was higher.The weight of autogenous bone grafted in PRP-FG-nHA/PA66 group was significantly smaller than that of PMMA group. In PRP-FG-nHA/PA66 group, the bone defect was morphologically repaired.

CONCLUSION

The study showed that PRP-FG-nHA/PA66 scaffold can significantly reduce the amount of autologous bone graft, and can achieve similar bone defect repair effect as PMMA. Our findings provide some reference and theoretical support for the treatment of large segmental bone defects in humans.

Differences in macrophage expression in induced membranes by fixation method - Masquelet technique using a mouse's femur critical-sized bone defect model

INTRODUCTION

Masquelet's induced membrane technique (MIMT) is an emerging method for reconstructing critical-sized bone defects. However, an incomplete understanding of the underlying biological and physical processes hinders further optimization. This study investigated the effect of different bone-defect fixation methods on macrophage expression in an induced membrane using a novel mouse plate-fixed Masquelet model.

METHODS

Mice were divided into Plate-fixed Masquelet (P-M), Intramedullary-fixed Masquelet (IM-M), Plate-fixed Control (P-C), and Back subfascial (B) groups. In the P-M and IM-M groups, a polymethylmethacrylate (PMMA) spacer was implanted into a 3 mm bone defect, while the defect in the P-C group remained unfilled. In group B, a spacer was inserted under the back fascia to examine membrane formation caused by a simple foreign body reaction. Tissues were collected at 1, 2, and 4 weeks postoperatively. Hematoxylin and eosin (H&E) staining and immunohistochemistry (CD68 and CD163: macrophage markers) were performed to assess macrophage expression within the membrane. qPCR was performed to measure the expression of CD68, CD163, and fibroblast growth factor 2 (FGF2).

RESULTS

Four weeks post-operation, the P-M group presented with minimal callus growth, whereas the IM-M group exhibited vigorous growth. The P-M and IM-M groups displayed a tri-layered membrane structure, which is consistent with the results of previous studies. The IM-M group had significantly thicker membranes, whereas the P-M group exhibited higher expression levels of CD68, CD163, and FGF2. Group P-C showed no osteogenesis, whereas group B maintained a thin, cell-dense membrane structure. The P-M group consistently showed higher gene expression levels than the P-C and P-B groups.

CONCLUSION

This study introduced a mouse plate fixation model for MIMT. The induced membranes could be adequately evaluated in this model. Induced membranes are formed by foreign body reactions to PMMA spacers; however, their properties are clearly different from those of simple foreign body reaction capsules and granulation tissues that infiltrate bone defects, suggesting that they are more complex tissues. The characteristics and expression of macrophages within these induced membranes varied according to the bone defect fixation method.

Induced-membrane technique for lower limb reconstruction after malignant bone tumour resection in paediatric patients: Complication and re-operation rates

BACKGROUND

The objective of this study was to assess the complication and re-operation rates, evaluate the risk of non-union, and describe the functional outcomes at last follow-up in children and adolescents after lower-limb malignant tumour resection and reconstruction using the induced-membrane technique.

HYPOTHESIS

Weight-bearing resumption 6 weeks after the second stage of the induced-membrane procedure promotes bone healing.

MATERIAL AND METHODS

The study included 13 patients (9 with osteosarcoma, 3 with Ewing's sarcomas, and 1 with alveolar sarcoma) managed between 2000 and 2020 by oncological femoral or tibial resection followed, at a distance from adjuvant chemotherapy, by reconstruction using the induced-membrane technique. Non-union was the primary outcome measure and the MusculoSkeletal Tumor Society (MSTS) lower-limb functional score was the secondary outcome measure. Mean follow-up was 6.1 years (range, 2.0-12.7). At last follow-up, mean age was 18.1 years (range, 11.0-26.0) and the mean MSTS score was 66.6% (37.0-93.0%).

RESULTS

After the second reconstruction stage, 8 complications developed in 6 patients (46%). Either a complication or limb-length inequality required 12 re-operations in 8 patients (61.5%). Non-union occurred after reconstruction in 5 (38.5%) patients. Early resumption of 50% weight-bearing 6 weeks after reconstruction was associated with bone healing (p=0.02).

CONCLUSION

The non-union rate was 38.5%. Partial, 50% weight-bearing with two elbow crutches and an orthosis, if allowed by construct stability, may promote bone healing.

LEVEL OF EVIDENCE

IV.

Use of F18 bioglass putty for induced membrane technique in segmental bone defect of the radius in rabbits

PURPOSE

To evaluate the inductive capacity of F18 bioglass putty on the induced membrane technique in a segmental bone defect of the rabbit's radius.

METHODS

Ten female Norfolk at 24 months of age were used. The animals were randomly separated based on postoperative time points: five rabbits at 21 and four at 42 days. A 1-cm segmental bone defect was created in both radii. The bone defects were filled with an F18 bioglass putty.

RESULTS

Immediate postoperative radiographic examination revealed the biomaterial occupying the segmental bone defect as a well-defined radiopaque structure with a density close to bone tissue. At 21 and 42 days after surgery, a reduction in radiopacity and volume of the biomaterial was observed, with particle dispersion in the bone defect region. Histologically, the induced membrane was verified in all animals, predominantly composed of fibrocollagenous tissue. In addition, chondroid and osteoid matrices undergoing regeneration, a densely vascularized tissue, and a foreign body type reaction composed of macrophages and multinucleated giant cells were seen.

CONCLUSIONS

the F18 bioglass putty caused a foreign body-type inflammatory response with the development of an induced membrane without expansion capacity to perform the second stage of the Masquelet technique.

Mechanisms of the Masquelet technique to promote bone defect repair and its influencing factors

The Masquelet technique, also known as the induced membrane technique, is a surgical technique for repairing large bone defects based on the use of a membrane generated by a foreign body reaction for bone grafting. This technique is not only simple to perform, with few complications and quick recovery, but also has excellent clinical results. To better understand the mechanisms by which this technique promotes bone defect repair and the factors that require special attention in practice, we examined and summarized the relevant research advances in this technique by searching, reading, and analysing the literature. Literature show that the Masquelet technique may promote the repair of bone defects through the physical septum and molecular barrier, vascular network, enrichment of mesenchymal stem cells, and high expression of bone-related growth factors, and the repair process is affected by the properties of spacers, the timing of bone graft, mechanical environment, intramembrane filling materials, artificial membrane, and pharmaceutical/biological agents/physical stimulation.

Fibromodulin facilitates the osteogenic effect of Masquelet's induced membrane by inhibiting the TGF-β/SMAD signaling pathway

Masquelet's induced membrane (IM) technique is a promising treatment strategy for the repair of substantial bone defects. The formation of an IM around polymethylmethacrylate bone cement plays a crucial role in this technique. Several studies have indicated that IMs have bioactivity because they contain abundant blood vessels, a variety of cells, and biological factors. The bioactivity of an IM increases during the initial stages of formation, thereby facilitating bone regeneration and remodeling. Nevertheless, the precise mechanisms underlying the enhancement of IM bioactivity and the promotion of bone regeneration necessitate further investigation. In this study, we successfully developed a Masquelet IM model of critical femur defects in rats. By employing proteomics analysis and biological detection techniques, we identified fibromodulin (FMOD) as a pivotal factor contributing to angiogenesis and the enhanced bioactivity of the IM. A significant increase in angiogenesis and the expression of bioactive factors in the IM was also observed with the upregulation of FMOD expression. Furthermore, this effect is mediated through the inhibition of the transforming growth factor beta (TGF-β)/SMAD signaling pathway. We also demonstrated that administering recombinant human FMOD enhanced osteogenesis in rat bone marrow mesenchymal stem cells and angiogenesis in human umbilical vein endothelial cells in vitro. Furthermore, the negative regulatory effect of the TGF-β signaling pathway was verified. In conclusion, this study provides a novel theoretical basis for the application of IMs in bone-defect reconstruction and explores possible new mechanisms that may play an important role in promoting the bioactivity and osteogenic potential of IMs.

Comparison of osteogenic activity from different parts of induced membrane in the Masquelet technique

BACKGROUND

The Masquelet technique is widely used to treat long-bone segmental defects because of its high success rate and low surgical difficulty. However, the cause of the uneven growth of bone grafts following this procedure remains unclear.

METHODS

Rats were randomly divided into four groups for analysis 2-, 4-, 6- and 8-weeks postoperatively and underwent a uniform surgical procedure to construct a 10 mm bone defect in the right posterior branch of the femur. Induced membrane specimens were harvested at the appropriate time points and divided into segments according to their location. Bone growth activity was assessed by immunohistochemistry, western blotting, and quantitative real-time polymerase chain reaction.

RESULTS

Mature blood vessels were more densely distributed at the proximal end of the bone defect than at other locations at all time points. The number of blood vessels on the same side of the longitudinal axis of the femur also varied depending on location. The difference between the proximal-anterior and distal-anterior regions within the induced membranes was most pronounced at 6 weeks postoperatively and decreased by 8 weeks postoperatively. The differences between the proximal-posterior and distal-posterior regions within the induced membranes were more pronounced. The expression of the growth factors bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor A(VEGFA), and transforming growth factor-β1(TGF-β1) in the proximal-posterior regions of the bone defect was almost always higher than that in other regions at the same time point. The expression of BMP-2 in the posterior regions of the bone defect was always higher than that in the anterior regions at the same end of the femoral longitudinal axis.

CONCLUSION

The number and maturation of vessels in the proximal region of the induced membrane at the bone defect site were higher than those in the distal region, and the expression of growth factors was higher, with the highest induced membrane activity in the proximal-posterior regions of the bone defect. Therefore, there was inhomogeneity in induced membrane activity.

Characterization of the Masquelet Induced Membrane Technique in a Murine Segmental Bone Defect Model

Objective  To reproduce in an animal model the surgical technique of Masquelet used in the treatment of critical bone defects and to analyze the characteristics of the membrane formed around the bone cement. Methods  A 10mm critical defect was created in the femoral shaft of 21 Sprague-Dawley rats. After resection of the central portion of the diaphysis, the defect was stabilized with a Kirschner wire introduced through the medullary canal and with the interposition of a bone cement spacer. After 2, 4, and 6 weeks of the surgical procedure, the animals were euthanized and evaluated on radiographs of the posterior limb regarding the size of the defect, alignment and stability of the osteosynthesis. The membranes formed around the spacer were subjected to histological analysis to assess thickness, connective tissue maturation and vascular density. Results  Over time, the membranes initially made up of loose connective tissue were replaced by membranes represented by dense connective tissue, rich in thick collagen fibers. At six weeks, membrane thickness was greater (565 ± 208μm) than at four (186.9 ± 70.21μm, p = 0.0002) and two weeks (252.2 ± 55.1μm, p = 0.001). All membranes from the initial time showed foci of osteogenic differentiation that progressively reduced over time. Conclusion  In addition to the structural and protective function of the membrane, its intrinsic biological characteristics can actively contribute to bone regeneration. The biological activity attributed by the presence of foci of osteogenesis confers to the membrane the potential of osteoinduction that favors the local conditions for the integration of the bone graft.

An engineered periosteum for efficient delivery of rhBMP-2 and mesenchymal progenitor cells during bone regeneration

During bone regeneration, the periosteum acts as a carrier for key regenerative cues, delivering osteochondroprogenitor cells and crucial growth factors to the injured bone. We developed a biocompatible, 3D polycaprolactone (PCL) melt electro-written membrane to act as a mimetic periosteum. Poly (ethyl acrylate) coating of the PCL membrane allowed functionalization, mediated by fibronectin and low dose recombinant human BMP-2 (rhBMP-2) (10-25 μg/ml), resulting in efficient, sustained osteoinduction in vitro. In vivo, rhBMP-2 functionalized mimetic periosteum demonstrated regenerative potential in the treatment of rat critical-size femoral defects with highly efficient healing and functional recovery (80%-93%). Mimetic periosteum has also proven to be efficient for cell delivery, as observed through the migration of transplanted periosteum-derived mesenchymal cells to the bone defect and their survival. Ultimately, mimetic periosteum demonstrated its ability to deliver key stem cells and morphogens to an injured site, exposing a therapeutic and translational potential in vivo when combined with unprecedentedly low rhBMP-2 doses.

Questions about Using the Induced Membrane Technique to Manage Cases of Congenital Tibial Pseudarthrosis

The induced membrane technique is an innovative approach for repairing critical bone defects and has been applied recently in patients with congenital pseudarthrosis of the tibia (CPT). CPT is frequently associated with neurofibromatosis type 1 (NF1). Here, we briefly describe the clinical results of the induced membrane technique in NF1-deficient patients with CPT and in an animal model of CPT. Furthermore, we discuss the hypotheses used to explain inconsistent outcomes for the induced membrane technique in CPT-especially when associated with NF1.

Effect of low-intensity pulsed ultrasound on osteogenic differentiation of human induced membrane-derived cells in Masquelet technique

INTRODUCTION

The Masquelet technique is a relatively new method for large bone defect treatment. In this technique, grafted bone tissue is used, and after the cement is removed, the induced membrane (IM; that form around the cement spacers placed in the bone defect region) is thought to play an important role in promoting bone formation. On the other hand, low-intensity pulsed ultrasound (LIPUS) is known to promote fracture healing and angiogenesis through mechanical stimulation. This study aimed to investigate the in vitro effects of LIPUS on the osteogenic differentiation of human induced membrane-derived cells (IMCs).

METHODS

Seven patients who had been treated using the Masquelet technique were enrolled. The IM was harvested during the second stage of the technique. IMCs were isolated, cultured in growth medium, and then divided into two groups: (1) control group, IMCs cultured in osteogenic medium without LIPUS, and (2) LIPUS group, IMCs cultured in osteogenic medium with LIPUS treatment. Adherent cells from the IM samples were harvested after the first passage and evaluated for cell surface protein expression using immunostaining. A cell proliferation assay was used to count the number of IMCs using a hemocytometer. Osteogenic differentiation capability was assessed using an alkaline phosphatase (ALP) activity assay, Alizarin Red S staining, and real-time reverse transcription-polymerase chain reaction.

RESULTS

Cell surface antigen profiling revealed that the IMCs contained cells positive for the mesenchymal stem cell-related markers CD73, CD90, and CD105. No significant difference in cell numbers was found between the control and LIPUS groups. The ALP activity of IMCs in the LIPUS group was significantly higher than that in the control group on days 7 and 14. Alizarin red S staining intensity was significantly higher in the LIPUS group than in the control group on day 21. Runx2 and VEGF expression was significantly upregulated on days 7 and 14, respectively, compared with levels in the control group.

CONCLUSION

We demonstrated the significant effect of LIPUS on the osteogenic differentiation of human IMCs. This study indicates that LIPUS can be used as an additional tool for the enhancement of the healing process of the Masquelet technique.

Does the use of antibiotic spacer disrupt induced membrane function?

Treatment of large segmental bone defects has been a challenging and long process for both physicians and patients. At present, the induced membrane technique is one of the reconstruction techniques commonly utilized in treating large segmental bone defects. It consists of a two-step procedure. In the first one, after bone debridement, the defect is filled with bone cement. The aim at this stage is to support and protect the defective area with cement. A membrane is formed around the area where cement was inserted 4-6 weeks after the first surgical stage. This membrane secretes vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), as shown in the earliest studies. In the second step, the bone cement is removed, and the defect is filled with cancellous bone autograft. In the first stage, antibiotics can be added to the applied bone cement, depending on the infection. Still, the histological and micromolecular effects of the added antibiotic on the membrane are unknown.This study investigates the molecular and histological effects of antibiotics addition into bone cement on the induced membrane.In this study, conducted on 27 male New Zealand rabbits, the 2 cm long defects of a bone were created in the rabbit femurs. Three groups were formed by placing antibiotic-free, gentamicin, and vancomycin-containing cement in the defect area.These groups were followed for six weeks, and the membrane formed at the end of 6 weeks was examined histologically. As a result of this study, it found that the membrane quality markers (Von Willebrand factor (vwf), Interleukin 6-8 (IL), Transforming growth factor beta (TGF-β), Vascular endothelial growth factor (VEGF) were significantly higher in the antibiotic-free bone cement group. Our study has shown that antibiotics added to the cement have negative effects on the membrane. Based on the results we obtained, it would be a better choice to use antibiotic-free cement in aseptic nonunions. However, more data is needed to understand the effects of these changes on the cement on the membrane.

The antibiotics supplemented bone cement improved the masquelet's induced membrane in a rat femur critical size defect model

BACKGROUND

Masquelet technique is a two-stage surgical procedure used in the treatment of critical-size bone defects (CSD). Adding antibiotics to polymethylmethacrylate (PMMA) is still questionable to create higher quality induced membrane (IM). The aim of the study was to evaluate the effects of three antibiotic-supplemented cement, fusidic acid, teicoplanin, and gentamicin, on osteogenesis and IM progression applied to rat femur CSD model by comparing histopathological, biochemical, and immunohistochemical findings.

METHODS

Twenty-eight male rats were divided into four groups control, gentamicin (G), teicoplanin (T), and fusidic acid (FA). A 10 mm CSD was created in rat femurs. In the postoperative 4th week, intracardiac blood samples were collected for biochemical analysis of bone alkaline phosphatase (BALP), osteocalcin (OC), and tumor necrosis factor-alpha (TNF-α) levels. IMs obtained in secondary operation were fixed and prepared for histopathological scoring of membrane progression and immunohistochemical evaluation of rat-specific Transforming Growth Factor-Beta (TGF-β), Runt-related Transcription Factor 2 (Runx2), and Vascular Endothelial Growth Factor (VEGF) expressions.

RESULTS

Levels of BALP and OC in serum didn't change among groups significantly while serum TNF-α levels significantly decreased in all antibiotic groups compared to the control group (P = 0.017). Histological scores of groups FA and T were significantly higher than those of groups Control and G (P = 0.0007). IMs of groups T and FA showed good progression while those of groups Control and G were also moderately progressed. A significant increase in TGF-β expression was observed in group G and FA (P = 0.001) while a significant increase in the expression of VEGF was observed in groups G and T compared to the control group (P = 0.036).

CONCLUSIONS

The bone cement impregnated with thermostable and safe antibiotics, gentamicin, fusidic acid, and teicoplanin can increase osteogenesis and support IM progression by increasing the expressions of TGF-β and VEGF. Anabolic effects of induced membranes used in the treatment of critical-size bone defects can be enhanced by antibiotic-supplemented PMMAs applied by altering the original technique.

Time-varying characteristics of the induced membrane and its effects on bone defect repair

PURPOSE

This study intended to determine the properties of induced membranes after various periods of polymethyl methacrylate (PMMA) retention and the effect of different retention intervals on subsequent defect repair.

METHODS

Model of a critical bone defect in rabbits was prepared to obtain the induced membrane. For varying intervals of spacer insertion (2, 4, 6, 8, 12, 16, and 20 weeks postoperatively), angiogenesis, osteogenesis, and MSC-related properties were analyzed by immunohistochemistry and western-blot. Furthermore, 2, 4, 6, and 8 weeks after PMMA insertion, bone grafting was performed. Characteristics of defect repair were analyzed by X-ray and micro-CT analysis.

RESULTS

The induced membrane displayed angiogenesis, osteogenesis, and MSC-related properties from the 2- to 20-week intervals. Quantitation of protein expression (RUNX2, ALP, VEGF, TGF-beta, OCT4, and STRO1) revealed that selected proteins gradually rose to a high level at 4-8 weeks postoperatively and then decreased to a low level over a long time period. Following bone grafting, the most new bone formation was in the group when grafting was performed at 4 weeks, followed by the groups at 2 and 6 weeks, with the least in the group at 8 weeks.

CONCLUSION

The induced membrane displays angiogenesis, osteogenesis, and MSC-related properties from the 2- to 20-week intervals. These were increased to a peak level at 4-8 weeks postoperatively and then gradually decreased. The optimal timing for bone grafting at the second stage in the presented model was 4 weeks after PMMA insertion.

Ternary regulation mechanism of Rhizoma drynariae total flavonoids on induced membrane formation and bone remodeling in Masquelet technique

CONTEXT

Rhizoma drynariae total flavonoids (RDTF) are used to treat fractures. CD31hiEmcnhi vessels induced by PDGF-BB secreted by osteoclast precursors, together with osteoblasts and osteoclasts, constitute the ternary regulatory mechanism of bone tissue reconstruction.

OBJECTIVE

This study aimed to determine whether RDTF can promote bone tissue remodeling and induce membrane growth in the rat Masquelet model and to explore its molecular mechanism based on the ternary regulation theory.

METHODS

Thirty-six SD rats were randomized to three groups: blank, induced membrane, and RDTF treatment (n = 12/group). The gross morphological characteristics of the new bone tissue were observed after 6 weeks. Sixty SD rats were also randomized to five groups: blank, induction membrane, low-dose RDTF, medium-dose RDTF, and high-dose RDTF (n = 12/group). After 4 weeks, immunohistochemistry and western blot were used to detect the expression of membrane tissue-related proteins. The mRNA expression of key factors of ternary regulation was analyzed by qRT-PCR.

RESULTS

RDTF positively affected angiogenesis and bone tissue reconstruction in the bone defect area. RDTF could upregulate the expression of key factors (PDGF-BB, CD31, and endomucin), VEGF, and HMGB1 mRNA and proteins in the ternary regulation pathway.

DISCUSSION AND CONCLUSION

Although the expected CD31hiEmcnhi vessels in the induction membrane were not observed, this study confirmed that RDTF could promote the secretion of angiogenic factors in the induced membrane. The specific mechanisms still need to be further studied.

The Combination of Platelet Rich Plasma Gel, Human Umbilical Mesenchymal Stem Cells and Nanohydroxyapatite/polyamide 66 Promotes Angiogenesis and Bone Regeneration in Large Bone Defect

BACKGROUND

In the present study, a novel tissue engineering bone graft including platelet rich plasma gel (PRP gel), human umbilical mesenchymal stem cells (HUMSCs) and nanohydroxyapatite/polyamide 66 (nHA-PA66) was constructed. We explored whether the composite scaffolds could enhance the angiogenesis and bone repair capacity in rat femoral large bone defect (LBD). This study aimed to provide evidence for the clinical application of the composite scaffold in LBD treatment.

METHODS

PRP was prepared, the platelets and growth factors were measured. HUMSCs were isolated and identified. the osteogenic capacity of PRP in vitro was measured. Then HUMSCs-PRP-gel/nHA-PA66 composite scaffolds were synthesized and observed. The proliferation and osteogenesis differentiation of HUMSCs on the composite scaffold was measured. The angiogenic capacity of PRP in vitro was measured by capillary-like tube formation assay. Finally, the angiogenesis and bone repair capacity of the composite scaffolds was measured in rat LBD.

RESULTS

PRP contained high level of platelets and growth factors after activation, and promoted osteogenic and angiogenic differentiation in vitro. The HUMSCs-PRP-gel/nHA-PA66 composite scaffold was porosity and promoted the proliferation and osteogenesis differentiation of HUMSCs. At 12th weeks, more micro-vessels and new bone were formed around the composite scaffolds compared with other groups, the defect was almost repaired.

CONCLUSION

Our study for the first time identified that the combination of PRP gel, HUMSCs and nHA-PA66 scaffold could significantly promote angiogenesis and bone regeneration in rat LBD, which may have implications for its further application in clinical LBD treatment.

Influence of the Immune Microenvironment Provided by Implanted Biomaterials on the Biological Properties of Masquelet-Induced Membranes in Rats: Metakaolin as an Alternative Spacer

Macrophages play a key role in the inflammatory phase of wound repair and foreign body reactions-two important processes in the Masquelet-induced membrane technique for extremity reconstruction. The macrophage response depends largely on the nature of the biomaterials implanted. However, little is known about the influence of the macrophage microenvironment on the osteogenic properties of the induced membrane or subsequent bone regeneration. We used metakaolin, an immunogenic material, as an alternative spacer to standard polymethylmethacrylate (PMMA) in a Masquelet model in rats. Four weeks after implantation, the PMMA- and metakaolin-induced membranes were harvested, and their osteogenic properties and macrophage microenvironments were investigated by histology, immunohistochemistry, mass spectroscopy and gene expression analysis. The metakaolin spacer induced membranes with higher levels of two potent pro-osteogenic factors, transforming growth factor-β (TGF-β) and bone morphogenic protein-2 (BMP-2). These alternative membranes thus had greater osteogenic activity, which was accompanied by a significant expansion of the total macrophage population, including both the M1-like and M2-like subtypes. Microcomputed tomographic analysis showed that metakaolin-induced membranes supported bone regeneration more effectively than PMMA-induced membranes through better callus properties (+58%), although this difference was not significant. This study provides the first evidence of the influence of the immune microenvironment on the osteogenic properties of the induced membranes.

Bone regeneration after marginal bone resection in two-stage treatment of chronic long bone infection - a combined histopathological and clinical pilot study

INTRODUCTION

In chronic bone infection, marginal bone resection avoids large and difficult to reconstruct bone defects. However, there is still a lack of knowledge on bone regeneration during chronic bone infection and bone healing capability after marginal bone resection. Therefore, the purpose of this study was to investigate the clinical and histopathological outcomes after marginal bone resection in chronic long bone infection. We hypothesized that there is a regenerative bone healing potential after marginal bone resection that results in an acceptable clinical outcome and improved pathohistological bone healing parameters during treatment.

MATERIALS AND METHODS

Nine patients were treated for chronic bone infections in a two-stage manner with marginal bone resection of the infected area and the placement of an antibiotic-loaded polymethyl methacrylate (PMMA) spacer at stage one followed by bone reconstruction at stage two combined with systemic antibiotic therapy. Comparable bone samples were harvested at the border region between vital and necrotic bone area during stage one and the identical location during stage two. Control bone samples were harvested from five healthy patients without bone infection. Clinical outcome in terms of infection eradication and bone consolidation were assessed. The phenotypic changes of osteocyte and morphological changes of lacunar-canalicular network were investigated by histological and immunohistochemical staining between the two observation periods. Furthermore, expression levels of major bone formation and resorption markers were investigated by immunohistochemical and tartrate-resistant acid phosphatase (TRAP) staining.

RESULTS

The clinical results with a follow-up of 12.9 months showed that eight of nine patients (88.9%) achieved bone consolidation after a planned two-stage procedure of marginal resection of necrotic bone and consecutive reconstruction. In four of the nine patients (44.4%), additional marginal debridements after stage two had to be performed. After marginal resection at stage one, the improved bone formation ability at stage two was demonstrated by significantly lower percentage of empty lacunae, significantly more mature osteocytes and higher BMP-2 positive cell density, whereas decreased resorption was indicated by significantly lower osteoclast density and RANKL/OPG ratio. In patients requiring additional debridement compared to patients without additional debridements, a significantly higher percentage of empty lacunae was found at stage one.

CONCLUSION

Marginal bone resection combined with local and systemic antibiotic therapy is a feasible treatment option to avoid large bone defects as bone from the marginal resection area seems to have good regenerative potential. Despite a high revision rate of 44.4%, this technique avoids large bone resection and revisions can be done by further marginal debridements.

Determination of the Elution Capacity of Dalbavancin in Bone Cements: New Alternative for the Treatment of Biofilm-Related Peri-Prosthetic Joint Infections Based on an In Vitro Study

Antibiotic-loaded bone cement is the most widely used approach for the treatment of biofilm-induced septic sequelae in orthopedic surgery. Dalbavancin is a lipoglycopeptide that acts against Gram-positive bacteria and has a long half-life, so we aimed to assess whether it could be a new alternative drug in antibiotic-loaded bone cement for the treatment of periprosthetic joint infections. We assessed the elution capacity of dalbavancin and compared it with that of vancomycin in bone cement. Palacos®R (Heraeus Medical GmbH, Wehrheim, Germany) bone cement was manually mixed with each of the antibiotics studied at 2.5% and 5%. Three cylinders were obtained from each of the mixtures; these were weighed and incubated in 5 mL phosphate-buffered saline at 37°C under shaking for 1 h, 2 h, 4 h, 8 h, 24 h, 48 h, 168 h, and 336 h. PBS was replenished at each time point. The samples were analyzed using high-performance liquid chromatography (vancomycin) and mass cytometry (dalbavancin). Elution was higher than the minimum inhibitory concentration (MIC)90 for both antibiotics after 14 days of study. The release of vancomycin at 14 days was higher than of dalbavancin at each concentration tested (p = 0.05, both). However, the cumulative release of 5% dalbavancin was similar to that of 2.5% vancomycin (p = 0.513). The elution capacity of dalbavancin reached a cumulative concentration similar to that of vancomycin. Moreover, considering that the MIC90 of dalbavancin is one third that of vancomycin (0.06 mg/L and 2 mg/L, respectively) and given the long half-life of dalbavancin, it may be a new alternative for the treatment of biofilm-related periprosthetic infections when loaded in bone cement.

Induced membrane technique for large bone defects: A systematic review and individual participant data meta-analysis

AIMS:

The aim of this study was to evaluate the efficacy of induced membrane technique (IMT), and to analyze the relationships between patient factors and surgical parameters as well as their impacts on achieving bone union and complication rates.

MATERIALS AND METHODS:

A comprehensive, computerized search of PubMed, Embase, and The Cochrane Library was conducted, and articles published from January 1, 1978 to February 1, 2021 were included. Clinical trials matching the following inclusion criteria were included: 1. published as a case series, case-controlled studies, or cohort study; 2. IMT was performed for more than 10 cases within the study. Univariate and multivariate logistic regression were performed with random intercepts to determine the association of specific predictor variables with nonunion rate, postoperative infection, the need for additional procedures, and time to union.

RESULTS:

Seventy eight trials were included in the study with a total of 3840 patients managed with IMT. Mean age was 38.6 (0.8–88) years, mean size of bone defects was 6.4 (0–25) cm primarily distributed in the tibia (n = 1814, 60.9%), and overall union rate was 87.6%. Multivariate analysis showed the odds of nonunion were significantly increased in patients with an interval between two stages from 8 to 12 weeks and ≥12 weeks. Patients with preoperative infection and addition of antibiotic to bone cement during IMT had significantly decreased odds of longer union time, but preoperative infection caused increased odds of additional surgery. External fixation throughout 2 stages had significantly increased odds of postoperative infection and additional surgery.

CONCLUSIONS:

We recommend that the timing of the second stage should be delayed until 6 to 8 weeks after the first stage. Bone cement with antibiotics can control the infection rate and shorten the healing time. Furthermore, there is no need to avoid using internal fixation due to possible concerns about causing postoperative infection.

Bone defect treatment: does the type and properties of the spacer affect the induction of Masquelet membrane? Evidence today

PURPOSE

High clinical success rates have been reported with the Masquelet technique in the treatment of traumatic bone loss. An increasing number of studies suggest that various factors can influence the properties of induced membranes. Goal of this systematic review is to answer the following questions: (1) which are the ideal spacer properties (material, surface topography, antibiotic supplementation) to booster the quality and osteogenic potential of induced membranes? (2) what is the ideal time to perform the second-stage operation?

METHODS

A systematic search using the keywords "((Masquelet) OR (Induced Periosteum)) AND ((Spacer) OR (Time))" was performed in PubMed, Embase and Cochrane Library according to PRISMA guidelines. Studies published up to the 23rd of February 2022 were included and assessed independently by two reviewers.

RESULTS

Thirteen animal and 1 clinical studies were identified to address the above questions. Spacer materials used were PMMA, silicone, titanium, polypropylene, PVA, PCL and calcium sulfate. With the exception of PVA sponges, all solid materials could induce membranes. Low union rates have been reported with titanium and rough surfaced spacers. Scraping of the inner surface of the IM also increased bony union rates. In terms of the ideal timing to perform the second-stage evidence suggests that membranes older than 8 weeks continue to have regenerative capacities similar to younger ones.

CONCLUSION

Membranes induced by smooth PMMA spacers loaded with low concentrations of antibiotics showed powerful osteogenic properties. Other materials such as Polypropylene or Calcium sulfate can also be used with good results. Despite current recommendation to perform the second stage operation in 4-8 weeks, membranes older than 8 weeks seem to have similar regenerative capacities to younger ones.

The induced membrane technique: Optimization of bone grafting in a rat model of segmental bone defect

INTRODUCTION

The induced membrane technique (IMT) is a two-stage surgical procedure used to treat fracture nonunion and bone defects. Although there is an increasing number of animal studies investigating the IMT, few have examined the outcomes of bone healing after a second stage grafting procedure. This study aimed at comparing two bone grafting procedures, as part of the IMT, in order to establish a rat model providing consistent healing outcomes.

METHODS

In male Fischer 344 rats, we created a 5 mm defect in the right femur, stabilized the bone with a plate and screws, and inserted a polymethylmethacrylate spacer into the defect. Four weeks later, the spacer was removed. Bone graft was harvested from a donor rat and placed into the defect, followed by membrane and wound closure. Experiments were conducted in two groups. In group 1 (n = 11), the bone graft contained a variable amount of cortical and cancellous bone, the time from donor euthanasia to grafting was up to 240 min, and one donor rat provided graft for 5-6 recipients. In group 2 (n = 12), we reduced the contribution of cortical bone to the graft, included bone marrow, and kept donor euthanasia to grafting time under 150 min. One donor was used per 3-4 recipients. The volume of graft per recipient and all other elements of the protocol were the same across groups. Bone healing at 12 weeks post grafting was compared radiographically by two orthopaedic surgeons in a blinded fashion, based on union status and a modified Lane & Sandhu score.

RESULTS

Healing rates improved from 36.4% in Group 1 to 91.6% in Group 2. There was a significant relationship between the methods and resulting union status (p = 0.004). The odds of achieving full union were significantly higher in group 2 compared to group 1 (odds ratio=19.25, 95% confidence interval [1.77-209.55]; p = 0.009). The average radiographic score was also significantly higher in group 2 (p = 0.005).

CONCLUSION

The revised bone grafting method significantly improved the healing outcomes and contributed to establishing a consistent rat model of the IMT. This model can benefit preclinical investigations by allowing for reliable and clinically-relevant comparisons.

Construction of adipose tissue using a silica expander capsule and cell sheet-assembled of decellularized adipose tissue

Delayed neovascularization and unstable adipose formation are major confounding factors in adipose tissue engineering. A system using decellularized adipose tissue (DAT), adipose-derived stem cells (ADSCs), and human umbilical vein endothelial cells (HUVECs) has been preliminarily studied, but it requires optimization, as adipogenic and angiogenic capabilities for maintaining a stable construct shape are limited. The current study aimed to address these limitations. Our initial modification involved the addition of exogenous chemokine (C-C motif) ligand 2 (CCL2), which resulted in enhanced adipogenesis and angiogenesis. However, further improvement was required due to delayed blood recanalization. To further optimize the system, a vascularized fibrous capsule derived from an implanted silica expander was utilized as a second modification. We hypothesized this would function as both a microbioreactor to fix the seed cells and exogenous CCL2 locally and as a vascular bed to promote neovascularization. Compared with that of the CCL2 loaded ADSC-HUVECs cell sheet assembled DAT system, adding the silica expander capsule resulted in significantly increased construct stability, new vessel intensity, a greater number of Oil Red O-positive lipid droplets, more enhanced tissue remodeling, and upregulated peroxisome proliferator-activated receptor gamma (PPARγ) & leptin expression. Thus, these two modifications helped optimize the currently available ADSC-HUVEC cell sheet assembled DAT system, providing an adipose tissue construction strategy with enhanced adipogenesis and angiogenesis to reconstruct soft tissue defects. Moreover, close-to-normal leptin expression provided the engineered adipose tissue with a glucometabolic function, in addition to remodeling capabilities. STATEMENT OF SIGNIFICANCE: Delayed neovascularization and unstable adipose formation are the two major problems in tissue engineering adipose. Here, we introduced an adipose tissue engineering construction strategy using a silica expander capsule along with hADSCs-HUVECs cell sheet-assembled DAT in a CCL2-rich microenvironment. Our data suggested that CCL2 could improve angiogenesis and adipogenesis in vitro and in vivo. The addition of tissue expander capsule could further improve the stability of construction and fabricated adipose tissue with increased new vessel intensity, greater numbers of Oil Red O-positive lipid droplets, more enhanced tissue remodeling, and upregulated leptin expression. CCL2 and expander capsule can have clinical utility for soft tissue defects repair, and these two factors can be useful in other tissue engineering.

The Induced Membrane Technique—The Filling Matters: Evaluation of Different Forms of Membrane Filling with and without Bone Marrow Mononuclear Cells (BMC) in Large Femoral Bone Defects in Rats

The Masquelet technique is used to treat large bone defects; it is a two-stage procedure based on an induced membrane. To improve the induced membrane process, demineralized bone matrix in granular (GDBM) and fibrous form (f-DBM) was tested with and without bone marrow mononuclear cells (BMC) as filling of the membrane against the gold standard filling with syngeneic cancellous bone (SCB). A total of 65 male Sprague–Dawley rats obtained a 5 mm femoral defect. These defects were treated with the induced membrane technique and filled with SCB, GDBM, or f-DBM, with or without BMC. After a healing period of eight weeks, the femurs were harvested and submitted for histological, radiological, and biomechanical analyses. The fracture load in the defect zone was lower compared to SCB in all groups. However, histological analysis showed comparable new bone formation, bone mineral density, and cartilage proportions and vascularization. The results suggest that f-DBM in combination with BMC and the induced membrane technique cannot reproduce the very good results of this material in large, non-membrane coated bone defects, nevertheless it supports the maturation of new bone tissue locally. It can be concluded that BMC should be applied in lower doses and inflammatory cells should be removed from the cell preparation before implantation.

Masquelet technique: Effects of vancomycin concentration on quality of the induced membrane

PURPOSE

The purpose of this study was to determine the effects of polymethylmetnacrylate (PMMA) spacer loaded with different concentrations of vancomycin on the proliferative, osteogenic, and angiogenic capacity of the induced membrane.

METHODS

Varying concentrations of vancomycin (0, 1, 2, 4, 6, 8, and 10 g) were fully mixed with bone cement powder (40 g), resulting in seven experimental groups. Hollow cylindrical PMMA spacers (10 mm height, 3 mm external diameter, and 0.8 mm internal diameter) were formed by a mold and submerged in phosphate-buffered saline for antibiotic release by spectrophotometry. Eighty-four New Zealand white rabbits were evenly randomized into seven groups, and segmental radius shaft defects (10 mm) were created. Defects were filled with cylindrical PMMA spacers containing different vancomycin concentrations, and subsequently underwent intramedullary fixation with a retrograde Kirschner's wire. Tissue toxicity was assessed and the proliferative, osteogenic, and angiogenic capacity of induced membranes were qualitatively analyzed by immunohistochemistry and real-time PCR.

RESULTS

No obvious toxicity was observed in the animal model. Alizarin red s staining and qualitative detection of type I collagen, CD31, Ki67, and STRO-1 by immunohistochemistry revealed an obvious decrease in the percentage of positively stained cells and in osteogenic capacity when the concentration of vancomycin was more than 6 g per cement dose. Quantitation of gene expression related to osteogenesis (Col1a, Alp, and Runx2), vascularization (Vegf, Tgfb1, and vWF), and proliferation (Oct4 and Stro-1) by real-time PCR revealed slight increases in the expression of selected genes at low vancomycin concentrations (1-4 g per cement dose), and relatively lower gene expression when the concentration of vancomycin was more than 6 g per cement dose.

CONCLUSION

PMMA spacers loaded with relatively low concentrations of vancomycin (1-4 g per cement dose) did not interfere with the proliferative, osteogenic, and angiogenic capacity of induced membranes, and even promoted their capacity. In contrast, spacers loaded with relatively high concentrations of vancomycin (6-10 g per cement dose) had negative effects on osteoblast viability, angiogenesis, and proliferation.

The induced membrane technique in animal models: a systematic review

Objectives:

Data Sources:

Study Selection:

Data Extraction:

Data Synthesis:

Conclusions:

Immunohistochemical analysis revealed the expression of bone morphogenetic proteins-4, 6, 7, and 9 in human induced membrane samples treated with the Masquelet technique

Background

Induced membrane (IM) is the key component of Masquelet reconstruction surgery for the treatment of bone defects. IM is formed around the cement spacer and is known to secrete growth factors and osteoinductive factors. However, there is limited evidence available concerning the presence of osteoinductive factors in IM. This study aimed to investigate the existence of bone morphogenetic proteins (BMPs) in IM harvested from patients during the treatment of bone defects using the Masquelet technique.

Methods

This study involved six patients whose bone defects had been treated using the Masquelet technique. The affected sites were the femur (n = 3) and the tibia (n = 3). During the second-stage surgery, 1 cm² pieces of IM were harvested. Histological sections of IM were immunostained with anti-BMP-4, 6, 7, and 9 antibodies. Human bone tissue served as the positive control.

Results

The presence of BMP-4, 6, 7, and 9 was observed in all IM samples. Further, immunolocalization of BMP-4, 6, 7, and 9 was observed in blood vessels and fibroblasts in all IM samples. Immunolocalization of BMP-4, 6, 7, and 9 was also observed in bone tissue within the IM in one sample, in which osteogenesis inside the IM was observed.

Conclusions

This study showed that osteoinductive factors BMP-4, 6, 7, and 9 were present in the IM harvested from patients, providing evidence indicating that the Masquelet technique effectively contributes to healing large bone defects. Therefore, it may be possible for surgeons to omit the addition of BMPs to bone grafts, given the endogenous secretion of BMPs from the IM.

The efficacy of combining a vascularized biogenic conduit and a decellularized nerve graft in the treatment of peripheral nerve defects: An experimental study using the rat sciatic nerve defect model

BACKGROUND

Although decellularized nerve grafts are often used as a bridging material in nerve defect repair, the lack of perfusion support in this procedure limits the regeneration capacity. To address this, we applied vascularized biogenic conduits, which are fibrous membranes prefabricated around the silicone rod that contain rich vascularity and macrophages, to nerve defect repair procedures using decellularized nerve grafts. The purpose of this study is to investigate the capacity of combining a vascularized biogenic conduit and a decellularized nerve graft for peripheral nerve regeneration using a 10-mm nerve defect model in rats.

MATERIALS AND METHODS

Sixteen adult male rats (F344 rats, 10-12 weeks, 200-250 g) were used in this study. For the prefabrication of vascularized biogenic conduits, a silicone rod was transplanted next to the sciatic nerve. After 8 weeks, this silicone rod was enveloped in connective tissue, called a vascularized biogenic conduit. The first rat was used to investigate the histological characteristics of vascularized biogenic conduits through immunofluorescence studies. The remaining 15 rats were divided into three groups to evaluate the efficacy of the combination of a decellularized nerve graft and a vascularized biogenic conduit: a decellularized nerve graft (DNG) group, a decellularized nerve graft with a vascularized biogenic conduit (DNG-w-VBC) group, and an autologous nerve graft (ANG) group. Eight weeks after nerve graft surgery, the assessment results of both functional recovery (electrophysical studies and target muscle atrophy) and morphological recovery (total number, diameter, and myelin thickness of the regenerated axons) of the regenerated nerves were examined.

RESULTS

Immunofluorescence studies revealed that the VBC contains extracellular matrix, vascular tissue, and macrophages. The results of the DNG-w-VBC group were superior to the DNG group in electrophysiological studies (CMAP; 6.29 ± 0.80% vs. 4.02 ± 3.35%, MNCV; 50.6 ± 8.4% vs. 25.7 ± 15.6%, p < .05, respectively), regenerated axon number (11,348 ± 812 vs. 7697 ± 2197, p < .05), and mean axon diameter (2.72 ± 0.33 μm vs. 1.64 ± 0.12 μm, p < .05).

CONCLUSIONS

Our study confirms that vascularized biogenic conduits supply vascularity and macrophages to nerve defect sites. Combining vascularized biogenic conduits with decellularized nerve grafts to treat nerve defects offers superior functional and morphological recovery of regenerated axons.

Is the bioactivity of induced membranes time dependent?

PURPOSE

The induced membrane technique (IMT) is a two-stage surgical procedure for reconstruction of bone defects. Bone grafting (second stage of IMT) is recommend after 4-8 weeks assuming the highest bioactivity of IMs. However, larger studies concerning the biology and maturation of IMs and a potential time dependency of the bioactivity are missing. Therefore, aim of this study was the time-dependent structural and cellular characterization of cement spacer IMs concomitantly to an analysis of membrane bioactivity.

METHODS

IMs from 60 patients (35-82 years) were obtained at different maturation stages (1-16 weeks). IMs were studied by histology and co-culture with mesenchymal stem cells (MSC). IM lysates were analyzed by ELISA and protein microarray.

RESULTS

Increasing vascularization and fibrosis were found in membranes older than 4 and 7 weeks, respectively. MSC grew out from all membranes and all membranes enhanced proliferation of cultured MSC. Osteocalcin and osteopontin (in membrane lysates or induced in MSC by membrane tissue) were found over all time points without significant differences. In contrast to alkaline phosphatase activity, increasing levels of osteoprotegerin were found in membranes.

CONCLUSION

The histological structure of IMs changes during growth and maturation, however, biologically active MSC and factors related to osteogenesis are found over all time points with minor changes. Thus, membranes older than 8 weeks exert regenerative capacities comparable to the younger ones. The postulated narrow time frame of 4-8 weeks until bone grafting can be questioned and surgeons may choose timing for the second operation more independently and based on other clinical factors.

The Masquelet Technique: Can Disposable Polypropylene Syringes be an Alternative to Standard PMMA Spacers? A Rat Bone Defect Model

BACKGROUND

Usually, the two-stage Masquelet induced-membrane technique for extremity reconstruction begins with a polymethylmethacrylate (PMMA) cement spacer-driven membrane, followed by an autologous cancellous bone graft implanted into the membrane cavity to promote healing of large bone defects. In exceptional cases, spacers made of polypropylene disposable syringes were successfully used instead of the usual PMMA spacers because of a PMMA cement shortage caused by a lack of resources. However, this approach lacks clinical evidence and requires experimental validation before being recommended as an alternative to the conventional technique.

QUESTIONS/PURPOSES

To (1) develop and (2) validate a critical-sized femoral defect model in rats for two stages of the Masquelet technique and to (3) compare the biological and bone healing properties of polypropylene-induced membranes and PMMA-induced membranes in this model.

METHODS

Fifty male Sprague Dawley rats aged 8 weeks old received a 6-mm femur defect, which was stabilized with an external fixator that was converted into an internal device. In the development phase, the defect was filled with PMMA in 16 rats to determine the most favorable timing for bone grafting. Two rats were excluded since they died of anesthetic complications. The other 14 were successively euthanized after 2 weeks (n = 3), 4 weeks (n = 4), 6 weeks (n = 4), and 8 weeks (n = 3) for induced membrane analyses. In the validation phase, 12 rats underwent both stages of the procedure using a PMMA spacer and were randomly assigned to two groups, whether the induced membrane was preserved or removed before grafting. To address our final objective, we implanted either polypropylene or PMMA spacers into the defect (Masquelet technique Stage 1; n = 11 rats per group) for the period established by the development phase. In each group, 6 of 11 rats were euthanized to compare the biological properties of polypropylene-induced membranes and PMMA-induced membranes using histological qualitative analysis, semiquantitative assessment of the bone morphogenic protein-2 content by immunostaining, and qualitative assessment of the mesenchymal stromal cell (MSC; CD31-, CD45-, CD90+, and CD73+ phenotypes) content by flow cytometry. Quantitative measurements from serum bone turnover markers were also performed. The five remaining rats of each group were used for Masquelet technique Stage 2, in which rat bone allografts were implanted in the induced membrane cavity after the polypropylene or PMMA spacers were removed. These rats recovered for 10 weeks before being euthanized for microCT quantitative measurements and bone histology qualitative assessment to evaluate and compare the extent of bone regeneration between groups.

RESULTS

Induced membrane analyses together with serum bone turnover measurements indicated that a 4-week interval time between stages was the most favorable. Removal of the induced membrane before grafting led to almost constant early implant failures with poor bone formation. Four-week-old rats with polypropylene-triggered induced membranes displayed similar histologic organization as rats with PMMA-driven induced membranes, without any difference in the cell density of the extracellular matrix (4933 ± 916 cells per mm2 for polypropylene versus 4923 ± 1284 cells per mm2 for PMMA; p = 0.98). Induced membrane-derived MSCs were found in both groups with no difference (4 of 5 with polypropylene versus 3 of 3 with PMMA; p > 0.99). Induced membrane bone morphogenic protein-2 immunolabeling and serum bone turnover marker levels were comparable between the polypropylene and PMMA groups. MicroCT analysis found that bone regeneration in the polypropylene group seemed comparable with that in the PMMA group (29 ± 26 mm3 for polypropylene versus 24 ± 18 mm3 for PMMA; p > 0.99). Finally, qualitative histological assessment revealed a satisfactory endochondral ossification maturation in both groups.

CONCLUSION

Using a critical-sized femoral defect model in rats, we demonstrated that polypropylene spacers could induce membrane encapsulation with histologic characteristics and bone regenerative capacities that seem like those of PMMA spacers.

CLINICAL RELEVANCE

In a same bone site, polymers with close physical properties seem to lead to similar foreign body reactions and induce encapsulating membranes with comparable bone healing properties. Polypropylene spacers made from disposable syringes could be a valuable alternative to PMMA. These results support the possibility of a cementless Masquelet technique in cases of PMMA shortage caused by a lack of resources.

Masquelet-Induced Membrane Characteristics in Chicken Radii Bone Defects

This study evaluated the formation of a Masquelet-induced membrane created through the formation of segmental bone defects in the radii of 15 healthy domestic chickens. When the chickens were in a surgical plane of anesthesia, a 1.5-cm segmental bone defect was produced in the left radius, which was subsequently filled with a bone cement spacer during its pasty polymerization phase. The bone defects were evaluated through radiographic imaging immediately after surgery and at 7, 15, 21, and 30 days after the creation of the bone defect. Five birds were euthanatized at 15, 21, and 30 days postoperatively for histological evaluation of the bone defect site. Immediate postoperative radiographic examination of the radii showed the presence of bone cement, which occupied the segmental bone defect. Thirty days after the surgical procedure, the presence of new bone formation at the fractured extremities was evident in the 5 remaining chickens. Histologically, the induced-membrane had 3 distinct zones at 15 days postoperatively, including 1 cell layer in contact with the bone cement spacer, 1 layer with collagen fibers, and 1 layer in contact with muscle, which was composed of disorganized connective tissue, active fibroblasts, and blood vessels. Twenty-one days after surgery, the zones were less defined, and there were metaplastic areas comprising cartilage and bone. Postoperative, diffuse mineralization of the membrane was observed 30 days after the surgical procedure. Formation of the induced membrane was observed during all periods of evaluation. The best histological characteristics for the Masquelet-induced membrane were detected 15 days after the formation of the bone defect, suggesting this would be the optimal time for second-stage surgery for bone reconstruction.

Masquelet's induced membrane technique: Review of current concepts and future directions

Masquelet's induced membrane technique (MIMT) is a relatively new, two-stage surgical procedure to reconstruct segmental bone defects. First performed by Dr. Masquelet in the mid-1980s, MIMT has shown great promise to revolutionize critical-sized bone defect repair and has several advantages over its alternative, distraction osteogenesis (DO). Also, its success in extremely challenging cases (defects > 15 cm) suggests that its study could lead to discovery of novel biological mechanisms that might be at play during segmental defect healing and fracture non-union. MIMT's advantages over DO have led to a world-wide increase in MIMT procedures over the past decades. However, MIMT often needs to be repeated and so the average initial success rate in adults lags significantly behind that of DO (86% vs 95%, respectively). The autologous foreign-body membrane created during the first stage by the immune system's response to a polymethyl methacrylate bone cement spacer is critical to supporting the morselized bone graft implanted in the second stage. However, the biological and/or physical mechanisms by which the membrane supports graft to bone union are unclear. This lack of knowledge makes refining MIMT and improving the success rates through technique improvements and patient selection a significant challenge and hinders wider adoption. In this review, current knowledge from basic, translational, and clinical studies is summarized. The dynamics of both stages under normal conditions as well as with drug or material perturbations is discussed along with perspectives on high-priority future research directions.

The induced membrane technique for bone defects: Basic science, clinical evidence, and technical tips

The clinical management of large bone defects continues to be a difficult clinical problem to manage for treating surgeons. The induced membrane technique is a commonly employed strategy to manage these complex injuries and achieve bone union. Basic science and clinical evidence continue to expand to address questions related to the biology of the membrane and how interventions may impact clinical outcomes. In this review, we discuss the basic science and clinical evidence for the induced membrane technique as well as provide indications for the procedure and technical tips for performing the induced membrane technique.

Comparison of amniotic membrane versus the induced membrane for bone regeneration in long bone segmental defects using calcium phosphate cement loaded with BMP-2

Thanks to its biological properties, the human amniotic membrane (HAM) combined with a bone substitute could be a single-step surgical alternative to the two-step Masquelet induced membrane (IM) technique for regeneration of critical bone defects. However, no study has directly compared these two membranes. We first designed a 3D-printed scaffold using calcium phosphate cement (CPC). We assessed its suitability in vitro to support human bone marrow mesenchymal stromal cells (hBMSCs) attachment and osteodifferentiation. We then performed a rat femoral critical size defect to compare the two-step IM technique with a single-step approach using the HAM. Five conditions were compared. Group 1 was left empty. Group 2 received the CPC scaffold loaded with rh-BMP2 (CPC/BMP2). Group 3 and 4 received the CPC/BMP2 scaffold covered with lyophilized or decellularized/lyophilized HAM. Group 5 underwent a two- step induced membrane procedure with insertion of a polymethylmethacrylate (PMMA) spacer followed by, after 4 weeks, its replacement with the CPC/BMP2 scaffold wrapped in the IM. Micro-CT and histomorphometric analysis were performed after six weeks. Results showed that the CPC scaffold supported the proliferation and osteodifferentiation of hBMSCs in vitro. In vivo, the CPC/BMP2 scaffold very efficiently induced bone formation and led to satisfactory healing of the femoral defect, in a single-step, without autograft or the need for any membrane covering. In this study, there was no difference between the two-step induced membrane procedure and a single step approach. However, the results indicated that none of the tested membranes further enhanced bone healing compared to the CPC/BMP2 group.

Expression of VEGF in Peripheral Serum Is a Possible Prognostic Factor in Bone-Regeneration via Masquelet-Technique-A Pilot Study

Two-step Masquelet-technique established a new procedure in the treatment of osseous defects, addressing prerequisites postulated by the “diamond concept”. Increase in blood perfusion and growth factors are enhanced by the “Masquelet-membrane”. To describe this, we measured serum levels of Vascular Endothelial Growth Factor (VEGF) of patients with atrophic non-unions of long bones undergoing Masquelet-technique. From over 500 non-union patients undergoing Masquelet-technique with prospective follow-up we randomly selected 30 patients. 23 were included, 7 lost to follow-up or excluded because of incomplete data. Serum was drawn at specified intervals before and after surgery. Patients were followed for at least 6 months after step 2. Classification into both groups was performed according to radiological results and clinical outcome 6 months after step 2. Concentration of VEGF in patients’ serum was performed via ELISA. 14 achieved osseous consolidation (responder group), 9 cases did not (non-responder). Responders showed a significant increase of serum-VEGF in the first and second week when compared to the preoperative values of step 1. Non-responders showed a significant increase of VEGF in the second week after Steps 1 and 2. Comparison of groups showed significantly higher increase of serum-VEGF week2 after step 1 and preoperative to step 2 for responders. Results show one possibility of illustrating therapeutic progress by monitoring growth factors and possibly allowing prognostic conclusions thereof. This might lead to a more targeted treatment protocol.

Comparison between Tonifying Kidney Yang and Yin in Treating Segmental Bone Defects Based on the Induced Membrane Technique: An Experimental Study in a Rat Model

Tonifying kidney therapy consisting of tonifying kidney yang and yin is the basic principle of Chinese medicine in treating segmental bone defects (SBDs). Previous studies have demonstrated the presence of the differences between tonifying kidney yang and yin in bone metabolism of osteoporosis and distraction osteogenesis models. However, whether the difference between the two tonifying kidney methods in bone repair for the induced membrane (IM) technique occurs or what is the difference remain unclear. Angiogeneic-osteogenic coupling plays an important role in bone repair and the induced membrane couples angiogenesis with the later osteogenesis during the IM process. This study aimed at investigating the effects of tonifying kidney yang (total flavonoids of Rhizoma Drynariae, TFRD) and yin (plastrum testudinis extract, PTE) on angiogenesis and osteogenesis in the IM-treated SBDs. Rats of 6 mm tibia bone defect model treated with IM were divided into five groups: the control group, the model group, the tonifying kidney yang group (TFRD-treated group), the tonifying kidney yin group (PTE-treated group), and the western medicine group. At 4 weeks after insertion of the polymethylmethacrylate (PMMA), three caudal vertebrae from the tail in each rat were implanted into the 6 mm defect gap. Radiographical, histological, immunohistochemical, and immunofluorescent analyses were performed to assess bone and vessel formation at 4 or 12 weeks after insertion of the PMMA, respectively. Our results revealed that TFRD and PTE were beneficial to both angiogenesis and osteogenesis. TFRD exerted a better effect on angiogenesis than PTE and achieved a better result in stage 1 rather than in stage 2 of IM, whereas PTE was superior to TFRD in osteogenesis and achieved a better result in stage 2 instead of stage 1. Collectively, these findings elucidated the beneficial effects of tonifying kidney yang and yin on angiogenesis and osteogenesis of SBD repair during the IM process, as well as the difference that tonifying kidney yang surpasses tonifying kidney yin in angiogenesis while tonifying kidney yin outperforms tonifying kidney yang in osteogenesis, which suggests that the combination between the application of tonifying kidney yang method in stage 1 of IM and tonifying kidney yin method in stage 2 may achieve better repair efficiency.

The induced membrane technique for the management of long bone defects

AIMS

The purpose of this study was to: review the efficacy of the induced membrane technique (IMT), also known as the Masquelet technique; and investigate the relationship between patient factors and technique variations on the outcomes of the IMT.

METHODS

A systematic search was performed in CINAHL, The Cochrane Library, Embase, Ovid MEDLINE, and PubMed. We included articles from 1 January 1980 to 30 September 2019. Studies with a minimum sample size of five cases, where the IMT was performed primarily in adult patients (≥ 18 years old), in a long bone were included. Multivariate regression models were performed on patient-level data to determine variables associated with nonunion, postoperative infection, and the need for additional procedures.

RESULTS

A total of 48 studies were included, with 1,386 cases treated with the IMT. Patients had a mean age of 40.7 years (4 to 88), and the mean defect size was 5.9 cm (0.5 to 26). In total, 82.3% of cases achieved union after the index second stage procedure. The mean time to union was 6.6 months (1.4 to 58.7) after the second stage. Our multivariate analysis of 450 individual patients showed that the odds of developing a nonunion were significantly increased in those with preoperative infection. Patients with tibial defects, and those with larger defects, were at significantly higher odds of developing a postoperative infection. Our analysis also demonstrated a trend towards the inclusion of antibiotics in the cement spacer having a protective effect against the need for additional procedures.

CONCLUSION

The IMT is an effective management strategy for complex segmental bone defects. Standardized reporting of individual patient data or larger prospective trials is required to determine the optimal implementation of this technique. This is the most comprehensive review of the IMT, and the first to compile individual patient data and use regression models to determine predictors of outcomes. Cite this article: Bone Joint J 2020;102-B(12):1723-1734.

Induced membrane technique: a critical literature analysis and proposal for a failure classification scheme

The reconstruction of long-bone segmental defects remains challenging, with the three common methods of treatment being bone transport, vascularized bone transfer, and the induced membrane technique (IMT). Because of its simplicity, replicability, and reliability, usage of IMT has spread all over the world in the last decade, with more than 300 papers published in the PubMed literature database on this subject so far. Most of the clinical studies have reported high rates of bone union, yet some also include more controversial results with frequent complications and revision surgeries. At the same time, various experimental research efforts have been designed to understand and improve the biological properties of the induced membrane. This literature review aims to provide an overview of IMT clinical results in terms of bone union and complications and to compare them with those of other reconstructive procedures. In light of our findings, we then propose an original classification scheme of IMT failures distinguishing between preventable and nonpreventable failures.

Effects of topical mechanical stability on the formation of Masquelet membrane in a rabbit radial defect model

The exact mechanism of Masquelet technique is unknown. This study intends to explore the effects of topical mechanical stability on the formation of Masquelet membrane. Segmental radius shaft defect was created in all rabbits, which were filled with polymethylmethacrylate (PMMA) in Non-fixation group, and with PMMA fixed with plates in Fixation group, and subjected to no disposal in control group. The topical stability of PMMA and plates were monitored via X-ray and mechanical test. And the membranes were excised for further Histological, IHC and Western-Blotting analysis 4 and 6 weeks post-operatively. X-ray revealed no sign of plates loosening, or shift of PMMA. Mechanical tests revealed superior topical stability by plates. Pathological examinations suggested that vascularized and osteogenic membranes were formed around PMMA. IHC and Western-Blotting analysis revealed that both Fixation and Non-fixation group exerted significant effects on the expression of Ki67, COL I, and CD31 positive cells, as well as the protein expression of osteogenic (RUNX2, ALP) and angiogenic (VEGFA, TGF-β1) factors. And compared with membrane in Non-fixation group, Fixing PMMA spacer with plates caused a significant increase in osteogenic and angiogenic expression. This study indicates that rigid fixation provided by plate in Masquelet technique positively alters the quality of membrane formed surrounding PMMA, in terms of significantly osteogenic and angiogenic potential.

Impact of scaffold granule size use in Masquelet technique on periosteal reaction: a study in rat femur critical size bone defect model

Purpose

The Masquelet technique for the treatment of large bone defects is a two-stage procedure based on an induced membrane. Compared to mature periosteum, the induced membrane differs significantly. However, both play a crucial role in bone regeneration. As part of a histological and radiological post-evaluation of an earlier project, we analyzed the influence of the granule size of the bone void filler Herafill^® on development of periosteum regrowth in a critical size defect.

Methods

We compared three different sizes of Herafill^® granules (Heraeus Medical GmbH, Wehrheim) in vivo in a rat femoral critical size defect (10 mm) treated with the induced membrane technique. After 8 weeks healing time, femurs were harvested and taken for histological and radiological analysis.

Results

A significantly increased regrowth of periosteum into the defect was found when small granules were used. Large granules showed significantly increased occurrence of bone capping. Small granules lead to significant increase in callus formation in the vicinity to the membrane.

Conclusion

The size of Herafill^® granules has significant impact on the development of periosteal-like structures around the defect using Masquelet’s induced membrane technique. Small granules show significantly increased regrowth of periosteum and improved bone formation adjacent to the induced membrane.

Evaluation of global gene expression in regenerate tissues during Masquelet treatment

The Masquelet induced-membrane (IM) technique is indicated for large segmental bone defects. Attributes of the IM and local milieu that contribute to graft-to-bone union are unknown. Using a rat model, we compared global gene expression profiles in critically sized femoral osteotomies managed using a cement spacer as per Masquelet to those left empty. At the end of the experiment, IM and bone adjacent to the spacer were collected from the Masquelet side. Nonunion tissue in the defect and bone next to the empty defect were collected from the contralateral side. Tissues were subjected to RNA isolation, sequencing, and differential expression analysis. Cell type enrichment analysis suggested the IM and the bone next to the polymethylmethacrylate (PMMA) spacer were comparatively enriched for osteoblastic genes. The nonunion environment was comparatively enriched for innate and adaptive immune cell markers, but only macrophages were evident in the Masquelet context. iPathwayGuide was utilized to identify cell signaling pathways and protein interaction networks enriched in the Masquelet environment. For IM vs nonunion false-discovery rate correction of P values rendered overall pathway differences nonsignificant, and so only protein interaction networks are presented. For the bone comparison, substantial enrichment of pathways and networks known to contribute to osteogenic mechanisms was revealed. Our results suggest that the PMMA spacer affects the cut bone ends that are in contact with it and at the same time induces the foreign body reaction and formation of the IM. B cells in the empty defect suggest a chronic inflammatory response to a large segmental osteotomy.

Induced-membrane treatment of refractory humeral non-union with or without bone defect

INTRODUCTION

Treatment of humeral non-union with or without bone defect is complex, with non-negligible rates of complication and failure. Few reports focused on management of treatment failure.

OBJECTIVE

The study hypothesis was that the induced-membrane technique associated in a 2-stage strategy to internal fixation provides systematic bone healing in refractory humeral non-union.

MATERIAL AND METHODS

The study included 15 patients, with a median age of 46.6 years, with humeral non-union of a mean 24 months' progression and mean history of 3 attempted revision surgeries. Seven patients showed bone defect, exceeding 5cm in 2 cases. Six had history of radial palsy.

RESULTS

Consolidation was achieved in all cases, at a mean 4.6 months. Ten patients underwent radial nerve transposition, 6 of whom had shown radial motor nerve palsy; all recovered within 2 to 5 months. There was 1 case of superficial infection, and 1 of seroma.

DISCUSSION

The induced-membrane technique ensures bone healing due to the biological properties of the membrane; the main drawback is the need for 2-stage surgery. When bone defect exceeds 5cm, a multi-perforated fibula segment can be placed inside the membrane to increase primary stability and enhance bone integration.

CONCLUSION

The induced-membrane technique is suited to humeral non-union, with or without bone defect. The 2-stage strategy is mandatory in case of suspected latent infection. In the 2-stage procedure, anteromedial radial nerve transposition facilitates the bone-graft stage.

LEVEL OF EVIDENCE

IV, retrospective study.

Induced Periosteum-Mimicking Membrane with Cell Barrier and Multipotential Stromal Cell (MSC) Homing Functionalities

The current management of critical size bone defects (CSBDs) remains challenging and requires multiple surgeries. To reduce the number of surgeries, wrapping a biodegradable fibrous membrane around the defect to contain the graft and carry biological stimulants for repair is highly desirable. Poly(ε-caprolactone) (PCL) can be utilised to realise nonwoven fibrous barrier-like structures through free surface electrospinning (FSE). Human periosteum and induced membrane (IM) samples informed the development of an FSE membrane to support platelet lysate (PL) absorption, multipotential stromal cells (MSC) growth, and the prevention of cell migration. Although thinner than IM, periosteum presented a more mature vascular system with a significantly larger blood vessel diameter. The electrospun membrane (PCL3%-E) exhibited randomly configured nanoscale fibres that were successfully customised to introduce pores of increased diameter, without compromising tensile properties. Additional to the PL absorption and release capabilities needed for MSC attraction and growth, PCL3%-E also provided a favourable surface for the proliferation and alignment of periosteum- and bone marrow derived-MSCs, whilst possessing a barrier function to cell migration. These results demonstrate the development of a promising biodegradable barrier membrane enabling PL release and MSC colonisation, two key functionalities needed for the in situ formation of a transitional periosteum-like structure, enabling movement towards single-surgery CSBD reconstruction.

The Masquelet technique: Current concepts, animal models, and perspectives

Bone reconstruction within a critical-sized defect remains a real challenge in orthopedic surgery. The Masquelet technique is an innovative, two-step therapeutic approach for bone reconstruction in which the placement of a poly (methylmethacrylate) spacer into the bone defect induces the neo-formation of a tissue called "induced membrane." This surgical technique has many advantages and is often preferred to a vascularized bone flap or Ilizarov's technique. Although the Masquelet technique has achieved high clinical success rates since its development by Alain-Charles Masquelet in the early 2000s, very little is known about how the process works, and few animal models of membrane induction have been developed. Our successful use of this technique in the clinic and our interest in the mechanisms of tissue regeneration (notably bone regeneration) prompted us to develop a surgical model of the Masquelet technique in rats. Here, we provide a comprehensive review of the literature on animal models of membrane induction, encompassing the defect site, the surgical procedure, and the histologic and osteogenic properties of the induced membrane. We also discuss the advantages and disadvantages of those models to facilitate efforts in characterizing the complex biological mechanisms that underlie membrane induction.

Vascularization Strategies in the Prevention of Nonunion Formation

Delayed healing and nonunion formation are major challenges in orthopedic surgery, which require the development of novel treatment strategies. Vascularization is considered one of the major prerequisites for successful bone healing, providing an adequate nutrient supply and allowing the infiltration of progenitor cells to the fracture site. Hence, during the last decade, a considerable number of studies have focused on the evaluation of vascularization strategies to prevent or to treat nonunion formation. These involve (1) biophysical applications, (2) systemic pharmacological interventions, and (3) tissue engineering, including sophisticated scaffold materials, local growth factor delivery systems, cell-based techniques, and surgical vascularization approaches. Accumulating evidence indicates that in nonunions, these strategies are indeed capable of improving the process of bone healing. The major challenge for the future will now be the translation of these strategies into clinical practice to make them accessible for the majority of patients. If this succeeds, these vascularization strategies may markedly reduce the incidence of nonunion formation. Impact statement Delayed healing and nonunion formation are a major clinical problem in orthopedic surgery. This review provides an overview of vascularization strategies for the prevention and treatment of nonunions. The successful translation of these strategies in clinical practice is of major importance to achieve adequate bone healing.

Introduction of a New Surgical Method to Improve Bone Healing in a Large Bone Defect by Replacement of the Induced Membrane by a Human Decellularized Dermis Repopulated with Bone Marrow Mononuclear Cells in Rat

The Masquelet technique for the treatment of large bone defects is a two-stage procedure based on an induced membrane. We eliminate the first surgical step by using a decellularized dermal skin graft (Epiflex^®) populated with bone marrow mononuclear cells (BMC), as a replacement for the induced membrane. The aim of this study was to demonstrate the feasibility of this technology and provide evidence of equivalent bone healing in comparison to the induced membrane-technique. Therefore, 112 male Sprague–Dawley rats were allocated in six groups and received a 10 mm femoral defect. Defects were treated with either the induced membrane or decellularized dermis, with or without the addition of BMC. Defects were then filled with a scaffold (β-TCP), with or without BMC. After a healing time of eight weeks, femurs were taken for histological, radiological and biomechanical analysis. Defects treated with Epiflex^® showed increased mineralization and bone formation predominantly in the transplanted dermis surrounding the defect. No significant decrease of biomechanical properties was found. Vascularization of the defect could be enhanced by addition of BMC. Considering the dramatic reduction of a patient’s burden by the reduced surgical stress and shortened time of treatment, this technique could have a great impact on clinical practice.