Osteoclasts and their precursors are present in the induced-membrane during bone reconstruction using the Masquelet technique

Improvements in Pediatric Bone Loss Reconstruction With the Induced Membrane Technique

BACKGROUND

The induced membrane technique is now widely used for pediatric diaphyseal bone loss due to various etiologies. Although consolidation rates remain satisfactory, complications, and healing delays may occur requiring additional procedures. We studied a series of induced membrane bone reconstructions in which the second stage included an embedded endomembranous non vascularized fibular shaft, in addition to iliac bone grafts. The purpose of this study was to analyze the results in terms of bone consolidation and complications.

METHODS

This is a retrospective comparative and multicentric study of 32 children with large bone loss treated with the induced membrane reconstruction technique. Patients were divided into 2 groups according to the graft used during the second stage. The first group (G1) of 16 patients had a nonvascularized fibula embedded inside the membrane in addition with the corticocancellous grafts from the iliac crest. The second group (G2) of 16 patients underwent reconstruction using the original technique, with iliac crest graft only.

RESULTS

The 2 groups were similar in terms of etiologies of bone loss and follow-up (mean: 44 mo for G1 and 49 mo for G2). Mean bone losses were 15.4 cm (range: 2 to 25; SD: 5.6) for G1 and 10.6 cm (range: 3 to 19; SD: 5.2) for G2. In the first group, all patients healed primarily, with a mean time of 5.9 months (range: 4 to 8; SD: 1.6). In the second group, 2 of 16 patients did not healed; for the others 14, healing mean time was 6.9 months (range: 3 to 12; SD: 2.7). The short-term and long-term complications rates were 38% to 19% for G1 and 50% to 31% for G2, respectively. Regarding the donor site, the fibulas reconstructed spontaneously with a mean time of 4.8 months (range: 3 to 6; SD: 1.2).

CONCLUSIONS

The integration of a nonvascularized fibula during the second stage of the induced membrane technique appears to improve the consolidation rate in the pediatric population.

LEVEL OF EVIDENCE

Level III-Retrospective comparative study.

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.

Comparative bone healing with induced membrane technique (IMT) versus empty defects in septic and aseptic conditions in a novel rabbit humerus model

BACKGROUND

Long bone defects resulting from primary trauma or secondary to debridement of fracture-related infection (FRI) remain a major clinical challenge. One approach often used is the induced membrane technique (IMT). The effectiveness of the IMT in infected versus non-infected settings remains to be definitively established. In this study we present a new rabbit humerus model and compare the IMT approach between animals with prior infection and non-infected equivalents.

METHODS

A 5 mm defect was created in the humerus of New Zealand White rabbits (n = 53) and fixed with a 2.5 mm stainless steel plate. In the non-infected groups, the defect was either left empty (n = 6) or treated using the IMT procedure (PMMA spacer for 3 weeks, n = 6). Additionally, both approaches were applied in animals that were inoculated with Staphylococcus aureus 4 weeks prior to defect creation (n = 5 and n = 6, respectively). At the first and second revision surgeries, infected and necrotic tissues were debrided and processed for bacteriological quantification. In the IMT groups, the PMMA spacer was removed 3 weeks post implantation and replaced with a beta-tricalcium phosphate scaffold and bone healing observed for a further 10 weeks. Infected groups also received systemic antibiotic therapy. The differences in bone healing between the groups were evaluated radiographically using a modification of the radiographic union score for tibial fractures (RUST) and by semiquantitative histopathology on Giemsa-Eosin-stained sections.

RESULTS

The presence of S. aureus infection at revision surgery was required for inclusion to the second stage. At the second revision surgery all collected samples were culture negative confirming successful treatment. In the empty defect group, bone healing was increased in the previously infected animals compared with non-infected controls as revealed by radiography with significantly higher RUST values at 6 weeks (p = 0.0281) and at the end of the study (p = 0.0411) and by histopathology with increased cortical bridging (80% and 100% in cis and trans cortical bridging in infected animals compared to 17% and 67% in the non-infected animals). With the IMT approach, both infected and non-infected animals had positive healing assessments.

CONCLUSION

We successfully developed an in vivo model of bone defect healing with IMT with and without infection. Bone defects can heal after an infection with even better outcomes compared to the non-infected setting, although in both cases, the IMT achieved better healing.

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.

Discovery of multipotent progenitor cells from human induced membrane: Equivalent to periosteum-derived stem cells in bone regeneration

Background

The periosteum stem cells (PSCs) plays a critical role in bone regeneration and defect reconstruction. Insertion of polymethyl methacrylate (PMMA) bone cement can form an induced membrane(IM) and showed promising strategy for bone defect reconstruction, the underlying mechanism remains unclear. Our study sought to determine whether IM-derived cells(IMDCs) versus PSCs have similar characteristics in bone regeneration.

Methods

IM and periosteum were harvested from ten bone defect patients treated with PMMA, the IMDCs and PSCs were isolated respectively. Morphological, functional and molecular evaluation was performed and matched for comparison.

Results

Both progenitor-like IMDCs and PSCs were successfully isolated. In vitro, we found IMDCs were similar to PSCs in morphology, colony forming capacity and expression of surface marker(CD90+, CD73+, CD105+, CD34-/CD45-). Meanwhile, these IMSCs displayed multipotency with chondrogenic, adipogenic and osteogenic differentiation, but differed in some IMSCs(3/10) population showing relatively poor osteogenic differentiation. The molecular profiles suggests that cell cycle and DNA replication signaling pathways were associated with these varying osteogenic potential. In vivo, we established a cell-based tissue-engineered bone by seeding IMDSs/PSCs to demineralized bone matrix (DBM) scaffold and demonstrated both IMDSs and PSCs enhanced bone regeneration in SCID mice bone defect model compared with DBM alone.

Conclusion

Our data demonstrated IM containing multipotent progenitor cells similar to that periosteum promoting bone regeneration, and indicated the existence of multiple subsets in osteogenic differentiation. Overall, the study provided a cellular and molecular insights in understanding the successful or failed outcome of bone defect healing.The translational potential of this article: This study confirmed IMDCs and PSCs share similar regeneration capacity and inform a translation potential of that cellular therapy applying IMDCs in bone defect repair.

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.

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.

Repair of critical diaphyseal defects of lower limbs by 3D printed porous Ti6Al4V scaffolds without additional bone grafting: a prospective clinical study

The repair of critical diaphyseal defects of lower weight-bearing limbs is an intractable problem in clinical practice. From December 2017, we prospectively applied 3D printed porous Ti6Al4V scaffolds to reconstruct this kind of bone defect. All patients experienced a two-stage surgical process, including thorough debridement and scaffold implantation. With an average follow-up of 23.0 months, ten patients with 11 parts of bone defects were enrolled in this study. The case series included three females and seven males, their defect reasons included seven parts of osteomyelitis and four parts of aseptic nonunion. The bone defects located at femur (five parts) and tibia (six parts), with an average defect distance of 12.2 cm. Serial postoperative radiologic follow-ups displayed a continuous process of new bone growing and remodeling around the scaffold. One patient suffered tibial varus deformity, and he underwent a revision surgery. The other nine patients achieved scaffold stability. No scaffold breakage occurred. In conclusion, the implantation of 3D printed Ti6Al4V scaffold was feasible and effective to reconstruct critical bone defects of lower limbs without additional bone grafting. Graphical abstract.

Masquelet technique in military practice: specificities and future directions for combat-related bone defect reconstruction

Because of its simplicity, reliability, and replicability, the Masquelet induced membrane technique (IMT) has become one of the preferred methods for critical bone defect reconstruction in extremities. Although it is now used worldwide, few studies have been published about IMT in military practice. Bone reconstruction is particularly challenging in this context of care due to extensive soft-tissue injury, early wound infection, and even delayed management in austere conditions. Based on our clinical expertise, recent research, and a literature analysis, this narrative review provides an overview of the IMT application to combat-related bone defects. It presents technical specificities and future developments aiming to optimize IMT outcomes, including for the management of massive multi-tissue defects or bone reconstruction performed in the field with limited resources.

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.

Efficacy of total flavonoids of Rhizoma drynariae on the blood vessels and the bone graft in the induced membrane

BACKGROUND

Total flavonoids of Rhizoma drynariae (TFRD), a Chinese medicine, is widely used in the treatment of orthopedic diseases. However, there are few basic and clinical studies on the effect of TFRD on induced membrane technique (Masquelet technique).

PURPOSE

This trial is to explore effects of TFRD on vascularization of the induced membrane, and mineralization of the bone graft in rats with femoral bone defects.

STUDY DESIGN AND METHODS

Forty-eight Sprague-Dawley rats were randomly divided into high dose group (H-TFRD), medium dose group (M-TFRD), low dose group (L-TFRD) and control group (control). The segmental bone defects were established with 12 rats in per group. The polymethyl methacrylate (PMMA) spacer was implanted into the femoral bone defect of rats in the first-stage surgery. About 4 weeks after first-stage surgery, induced membranes of 6 rats in each group were selected. The blood vessels and angiogenesis-related factors in the induced membrane were analyzed by hematoxylin-eosin (HE) and masson staining, western blot, qPCR and immunohistostaining. The remaining rats in per group underwent second-stage surgery (bone grafting). Twelve weeks after the bone grafting, the bone tissues was examined by X-ray, micro-computed tomography (Micro-CT), HE staining and enzyme-linked immunosorbent assay (ELISA) to evaluate the growth of the bone graft. Meanwhile, the TFRD-containing serum was collected from rats to culture osteoblasts in vitro. Cell Counting Kit-8 (CCK-8) method, Alizarin Red S (ARS) staining, western blot and immunofluorescence were used to detect effects of TFRD on the osteoblasts' proliferation and BMP-SMAD signaling pathway.

RESULTS

Compared with the L-TFRD and control groups, the number of blood vessels and the expression of angiogenesis-related factors (VEGF, TGF-β1, BMP-2, PDGF-BB and CD31) were higher in the H-TFRD and M-TFRD groups. The Lane-Sandhu X-ray score, bone mass and growth rate of the bone graft in the H-TFRD and M-TFRD groups were significantly better than those in the L-TFRD and control groups. In addition, medium and high doses of TFRD significantly increased the expression of BMP-SMAD pathway proteins (BMP-2, SMAD1, SMAD4, SMAD5 and RUNX2) in rat serum and bone graft. In vitro, after osteoblasts were intervened with TFRD-containing serum from the H-TFRD and M-TFRD groups, the cell viability, the number of mineralized nodules and the phosphorylation of BMP-SMAD pathway proteins were markedly increased.

CONCLUSION

TFRD could promote the formation of blood vessels and the expression of angiogenesis-related factors during the formation of the induced membrane. During the growing period of bone graft, it could facilitate the growth and mineralization of bone graft in a dose-dependent manner, which is partly related to the activation and phosphorylation of BMP-SMAD signaling pathway.

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 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.

Skeletal regeneration for segmental bone loss: Vascularised grafts, analogues and surrogates

Massive segmental bone defects (SBD) are mostly treated by removing the fibula and transplanting it complete with blood supply. While revolutionary 50 years ago, this remains the standard treatment. This review considers different strategies to repair SBD and emerging potential replacements for this highly invasive procedure. Prior to the technical breakthrough of microsurgery, researchers in the 1960s and 1970s had begun to make considerable progress in developing non autologous routes to repairing SBD. While the breaktthrough of vascularised bone transplantation solved the immediate problem of a lack of reliable repair strategies, much of their prior work is still relevant today. We challenge the assumption that mimicry is necessary or likely to be successful and instead point to the utility of quite crude (from a materials technology perspective), approaches. Together there are quite compelling indications that the body can regenerate entire bone segments with few or no exogenous factors. This is important, as there is a limit to how expensive a bone repair can be and still be widely available to all patients since cost restraints within healthcare systems are not likely to diminish in the near future. STATEMENT OF SIGNIFICANCE: This review is significant because it is a multidisciplinary view of several surgeons and scientists as to what is driving improvement in segmental bone defect repair, why many approaches to date have not succeeded and why some quite basic approaches can be as effective as they are. While there are many reviews of the literature of grafting and bone repair the relative lack of substantial improvement and slow rate of progress in clinical translation is often overlooked and we seek to challenge the reader to consider the issue more broadly.

Effect of low-level laser therapy on the membrane induced by the Masquelet technique at an orthotopic site in rabbits

Purpose:

To evaluate the low-level laser therapy (LLLT) on the membrane induced by the Masquelet technique in rabbits.

Methods:

Twelve Norfolk rabbits at approximately 3 months of age were used. A 1-cm segmental defect was induced in both radii, which were filled with polymethylmethacrylate cylinder. LLLT was used postoperatively in the bone defect of one of the forelimbs every 48 hours for 15 days. Six rabbits were euthanatized on third and sixth postoperative weeks.

Results:

In both forelimbs, radiographs showed new bone growth from radius cut ends on the third postoperative week and more advanced stage on the sixth postoperative week. Ultrasound showed induced membrane one week after the surgery. Histologically, there were no significant differences in the semi-quantitative score of inflammation intensity, total number of blood vessels, bone metaplasia, and collagen. The average thicknesses were 2,050.17 and 1,451.96 μm for control membranes and 2,724.26 and 2,081.03 μm for irradiated membranes, respectively, on third and sixth postoperative weeks. Vascular endothelial growth factor A (VEGF-A) and platelet derived growth factor (PDGF) expression were present in the induced membranes of control and irradiated forelimbs, but there was no significant difference.

Conclusions:

Based on assessment methods, it was not possible to demonstrate the effect of LLLT on the induced membrane.

Strategies for large bone defect reconstruction after trauma, infections or tumour excision: a comprehensive review of the literature

Large bone defects resulting from musculoskeletal tumours, infections, or trauma are often unable to heal spontaneously. The challenge for surgeons is to avoid amputation, and provide the best functional outcomes. Allograft, vascularized fibular or iliac graft, hybrid graft, extracorporeal devitalized autograft, distraction osteogenesis, induced-membrane technique, and segmental prostheses are the most common surgical strategies to manage large bone defects. Given its optimal osteogenesis, osteoinduction, osteoconduction, and histocompatibility properties, along with the lower the risk of immunological rejection, autologous graft represents the most common used strategy for reconstruction of bone defects. However, the choice of the best surgical technique is still debated, and no consensus has been reached. The present study investigated the current reconstructive strategies for large bone defect after trauma, infections, or tumour excision, discussed advantages and disadvantages of each technique, debated available techniques and materials, and evaluated complications and new perspectives.

Rat model of an autologous cancellous bone graft

Autologous cancellous bone (ACB) grafting is the "gold standard" treatment for delayed bone union. However, small animal models for such grafts are lacking. Here, we developed an ACB graft rat model. Anatomical information regarding the iliac structure was recorded from five rat cadavers (10 ilia). Additionally, 5 and 25 rats were used as controls and ACB graft models, respectively. A defect was created in rat femurs and filled with ACB. Post-graft neo-osteogenic potential was assessed by radiographic evaluation and histological analysis. Iliac bone harvesting yielded the maximum amount of cancellous bone with minimal invasiveness, considering the position of parailiac nerves and vessels. The mean volume of cancellous bone per rat separated from the cortical bone was 73.8 ± 5.5 mm³. Bone union was evident in all ACB graft groups at 8 weeks, and new bone volume significantly increased every 2 weeks (P < 0.001). Histological analysis demonstrated the ability of ACB grafts to act as a scaffold and promote bone union in the defect. In conclusion, we established a stable rat model of ACB grafts by harvesting the iliac bone. This model can aid in investigating ACB grafts and development of novel therapies for bone injury.

The Basic Science Behind the Clinical Success of the Induced Membrane Technique for Critical-Sized Bone Defects

»

The induced membrane technique (IMT) takes advantage of an osteoinductive environment that is created by the placement of a cement spacer into a bone defect.

»

Most commonly, a polymethylmethacrylate (PMMA) spacer has been used, but spacers made from other materials have emerged and achieved good clinical outcomes.

»

The IMT has demonstrated good results for long-bone repair; however, more research is required in order to optimize union rates as well as delineate more precise indications and surgical timing.

Total Flavonoids of Rhizoma Drynariae Promotes Differentiation of Osteoblasts and Growth of Bone Graft in Induced Membrane Partly by Activating Wnt/β-Catenin Signaling Pathway

Total flavonoids of Rhizoma drynariae (TFRD), a Chinese medicine, is widely used in the treatment of fracture, bone defect, osteoporosis and other orthopedic diseases, and has achieved good effects. Purpose of this trial was to explore efficacy of TFRD on bone graft’s mineralization and osteoblasts’ differentiation in Masquelet induced membrane technique in rats. Forty male Sprague-Dawley rats were randomly divided into high dose group (H-TFRD), middle dose group (M-TFRD), low dose group (L-TFRD) and control group (control). The critical size bone defect model of rats was established with 10 rats in each group. Polymethyl methacrylate (PMMA) spacer was implanted into the defect of right femur in rats. After the formation of the induced membrane, autogenous bone was implanted into the induced membrane. After 12 weeks of bone graft, bone tissues in the area of bone graft were examined by X-ray, Micro-CT, hematoxylin-eosin (HE) and Masson trichrome staining to evaluate the growth of the bone graft. The β-catenin, c-myc, COL1A1, BMP-2 and OPN in bone graft were quantitatively analyzed by Western blot and Immunohistostaining. Osteoblasts were cultured in the medium containing TFRD. Cell Counting Kit-8 (CCK-8) method, Alkaline phosphatase (ALP) and Alizarin Red S (ARS) staining, Western blot, RT-PCR and other methods were used to detect the effects of TFRD on the proliferation of osteoblasts and the regulation of Wnt/β-catenin signaling pathway. In vivo experiments showed that the growth and mineralization of bone graft in TFRD group was better. Moreover, the expression of Wnt/β-catenin and osteogenesis-related proteins in bone tissue of TFRD group was more than that in other groups. In vitro experiments indicated that osteoblasts proliferated faster, activity of ALP was higher, number of mineralized nodules and proteins related to osteogenesis were more in TFRD group. But blocking Wnt/β-catenin signaling pathway could limit these effects. Therefore, TFRD could promote mineralization of bone graft and differentiation of osteoblasts in a dose-dependent manner during growing period of the bone graft of induced membrane technique, which is partly related to the activation of Wnt/β-catenin signaling pathway.

Oxidation-Responsive, Tunable Growth Factor Delivery from Polyelectrolyte-Coated Implants

Polyelectrolyte multilayer (PEM) coatings, constructed on the surfaces of tissue engineering scaffolds using layer-by-layer assembly (LbL), promote sustained release of therapeutic molecules and have enabled regeneration of large-scale, pre-clinical bone defects. However, these systems primarily rely on non-specific hydrolysis of PEM components to foster drug release, and their pre-determined drug delivery schedules potentially limit future translation into innately heterogeneous patient populations. To trigger therapeutic delivery directly in response to local environmental stimuli, an LbL-compatible polycation solely degraded by cell-generated reactive oxygen species (ROS) was synthesized. These thioketal-based polymers were selectively cleaved by physiologic doses of ROS, stably incorporated into PEM films alongside growth factors, and facilitated tunable release of therapeutic bone morphogenetic protein-2 (BMP-2) upon oxidation. These coatings' sensitivity to oxidation was also dependent on the polyanions used in film construction, providing a simple method for enhancing ROS-mediated protein delivery in vitro. Correspondingly, when implanted in critically-sized rat calvarial defects, the most sensitive ROS-responsive coatings generated a 50% increase in bone regeneration compared with less sensitive formulations and demonstrated a nearly threefold extension in BMP-2 delivery half-life over conventional hydrolytically-sensitive coatings. These combined results highlight the potential of environmentally-responsive PEM coatings as tunable drug delivery systems for regenerative medicine.

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.

Histological analysis of induced membranes in patients whose bone defects were treated with the Masquelet technique to identify factors affecting the vascularity of induced membranes

Background

Rich vascularity of the induced membrane (IM) is important for Masquelet reconstruction surgery. The factors affecting IM vascularity are not completely understood. This study aimed to investigate these factors using histological samples of human IMs.

Methods

We retrospectively evaluated 36 patients whose bone defects were treated using the Masquelet technique. Two clinical pathologists analyzed histological sections of IM pieces (1 cm²). The number of blood vessels per 1 mm² was counted and compared among men and women, femur or tibia, with and without free flap surgery, antibiotic impregnation to the cement, osteogenesis inside the membrane, smoking, and diabetes mellitus. The number of blood vessels within the same patient was compared among different time points. Correlation analysis was performed among blood vessel numbers and patient age, duration of cement spacer placement, and histological grading scales (inflammation, foreign body reaction, and fibrosis).

Results

IM formation with rich vascularity and some inflammation, foreign body reaction, and fibrosis were histologically confirmed in all patients. We found 37.4 ± 19.1 blood vessels per 1 mm². The number of blood vessels was significantly lower in patients with than in those without free flap surgery; it was higher in patients with osteogenesis inside the IM. No significant correlations were found in any of the analyses.

Conclusion

Sex, patient age, smoking, diabetes mellitus, femur or tibia, duration of cement spacer placement, and antibiotic impregnation to the cement did not affect IM vascularization. IM vascularization was reduced in patients with than in those without free flap surgery.

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.

Radiological and clinical outcomes using induced membrane technique combined with bone marrow concentrate in the treatment of chronic osteomyelitis of immature patients

Aims

Treatment of chronic osteomyelitis (COM) for young patients remains a challenge. Large bone deficiencies secondary to COM can be treated using induced membrane technique (IMT). However, it is unclear which type of bone graft is optimal. The goal of the study was to determine the clinical effectiveness of bone marrow concentrator modified allograft (BMCA) versus bone marrow aspirate mixed allograft (BMAA) for children with COM of long bones.

Methods

Between January 2013 and December 2017, 26 young patients with COM were enrolled. Different bone grafts were applied to repair bone defects secondary to IMT procedure for infection eradication. Group BMCA was administered BMCA while Group BMAA was given BMAA. The results of this case-control study were retrospectively analyzed.

Results

Patient infection in both groups was eradicated after IMT surgery. As for reconstruction surgery, no substantial changes in the operative period (p = 0.852), intraoperative blood loss (p = 0.573), or length of hospital stay (p = 0.362) were found between the two groups. All patients were monitored for 12 to 60 months. The median time to bone healing was 4.0 months (interquartile range (IQR) 3.0 to 5.0; range 3 to 7) and 5.0 months (IQR 4.0 to 7.0; range 3 to 10) in Groups BMCA and BMAA, respectively. The time to heal in Group BMCA versus Group BMAA was substantially lower (p = 0.024).

Conclusion

IMT with BMCA or BMAA may attain healing in large bone defects secondary to COM in children. The bone healing time was significantly shorter for BMCA, indicating that this could be considered as a new strategy for bone defect after COM treatment.

Cite this article: Bone Joint Res 2021;10(1):31–40.

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.

[Effect of glycoside of short-horned epimedium Herb on the expressions of transforming growth factor β 1 and basic fibroblast growth factor induced membrane by Masquelet technology]

Objective

To observe the expressions of transforming growth factor β ₁ (TGF-β ₁) and basic fibroblast growth factor (bFGF) induced membrane by Masquelet technique in rats treated with glycoside of short-horned epimedium Herb, and to explore the effect of glycoside of short-horned epimedium Herb on Masquelet induced membrane.

Methods

Sixty 3-month-old male Wistar rats were randomly divided into 3 groups with 20 rats in each group; a tibial bone defect (6 mm in length) model was established. The blank group (group A) was not treated; the control group (group B) and the experimental group (group C) were filled with vancomycin antibiotic bone cement in the drawing stage, and the bone cement was completely solidified. Group C was given perfused flavonoids glycoside of short-horned epimedium Herb (10 μmol/L) by gavage once a day (0.3 mL) from 1 day after operation, and groups A and B were given the same amount of normal saline by gavage. After operation, the recovery and wound healing of experimental animals were observed; at 4 weeks after operation, X-ray film was taken to observe the recovery of bone defect of proximal tibia; at 6 weeks after operation, the bone defect was observed, and the morphological changes and vascularization degree of granulation tissue and induction membrane tissue were observed; the expressions of TGF-β ₁ and bFGF were observed by immunohistochemistry staining and ELISA detection.

Results

The bone defect models of the 3 groups were established successfully, and there was no abnormality after operation. The incisions healed by first intention after operation. At 4 weeks after operation, X-ray films of proximal tibial defect showed that there was obvious space in group A, while bone cement was filled and Kirschner wire fixation was good in groups B and C. At 6 weeks after operation, the gross observation showed that the granulation tissue was filled in the defect area in group A; transparent membrane was formed in groups B and C, and microvessels were seen in some areas, and the microvessels in group C were significantly more than those in group B. Immunohistochemical staining showed that the expressions of TGF-β ₁ and bFGF were negative in group A, but they were expressed in groups B and C, and the expressions of TGF-β ₁ and bFGF in group B were significantly less than those in group C. ELISA detection showed that the expressions of TGF-β ₁ and bFGF in group C were significantly higher than those in groups A and B ( P<0.05), but there was no significant difference between groups A and B ( P>0.05).

Conclusion

Glycoside of short-horned epimedium Herb can significantly increase the expressions of TGF-β ₁ and bFGF, accelerate the process of osteogenesis, and contribute to bone shaping and reconstruction.

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.

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 membrane technique combined with antibiotic-loaded calcium sulfate-calcium phosphate composite as bone graft expander for the treatment of large infected bone defects: preliminary results of 12 cases

BACKGROUND

Management of large infected bone defects is a major clinical and socioeconomic problem. The induced membrane technique has been widely used as a solution. However, it has apparent disadvantages such as limited autologous bone graft supply and lack of continuous infection control. Meanwhile, calcium sulfate/calcium phosphate composites have efficacious osteogenesis and antibiotic delivery capacity. For the first time, we analyzed the efficiency of calcium sulfate/calcium phosphate composites as a bone graft expander in the induced membrane technique to treat large infected bone defects.

METHODS

We retrospectively analyzed the clinical data of 12 patients with large infected bone defects of 6.1-17.2 cm treated with the induced membrane technique from November 2016 to July 2019. In the second reconstruction stage, the bone defect was filled with a mixture of the autogenous iliac bone and vancomycin-impregnated calcium sulfate/calcium phosphate composites at a ratio of 3:1. We assessed the bony union by Samantha X-ray score and recorded infection recurrence and complications. Paley scale and SF-36 score were used to evaluate the function of adjacent joint and quality of life pre and postoperatively. Pearson's correlation coefficients were calculated for union time and other clinical scores.

RESULTS

The mean follow-up was 69 weeks (ranging from 30 to 142) after the second stage of the operation. The mean Samantha X-ray score was 5.1 [3-6], preoperative and postoperative SF-36 scores showed that there were statistical differences in all the nine aspects, and the excellent rate of adjacent joint function was 75% (Paley). All cases were radiologically healed, and none of the 12 patients had infection recurrence or failure of fixation at the last follow-up. Two cases had delayed wound healing and were cured after dress changing. There was a significant correlation between union time and Samantha X-ray score (r =‒0.887; P=0.000), while there was no correlation between filling dose, size of the defect, and other outcomes.

CONCLUSIONS

This study provided evidence supporting calcium sulfate/calcium phosphate composites as an effective and safe bone graft expander in the induced membrane technique to treat large infected bone defect. This technique may help decrease the use of autologous bone graft and enhance the anti-infection effect of the induced membrane technique.

Repeated Induced-Membrane Technique Failure without Infection: A Series of Three Consecutive Procedures Performed for a Single Femur Defect

A 40-year-old male was treated using the induced-membrane technique (IMT) for a noninfected, 9 cm long femoral bone defect complicating a lengthening procedure. The interesting case feature lies in the three consecutive IMT procedures that were necessary to achieve complete bone repair in this unusual clinical situation. The first procedure failed because of the lack of graft revascularization likely related to an induced-membrane (IM) alteration demonstrated by histological observations. The second IMT procedure led to partial graft integration interrupted by the elongation nail breakage. At last, the third procedure fully succeeded after nail exchange and iterative iliac bone grafting. Complete bone union was achieved with a poor functional recovery one year after the last procedure and four years following the first cement spacer implantation. By means of clinical and histological observations, we demonstrated that the first and the second IMT failures had two distinct origins, namely, biological and mechanical causes, respectively. Although simple, a successful IMT procedure is not so easy to complete.

[Clinical study on treatment of chronic infection of foot and ankle with lower extremity ischemic diseases by tibial transverse transport combined with antibiotic embedded bone cement]

Objective

To study the effectiveness of tibial transverse transport combined with the antibiotics embedded bone cement in the treatment of chronic infection of foot and ankle with lower extremity ischemic diseases.

Methods

A retrospective analysis was performed on 28 patients with ischemic diseases of lower extremities associated with chronic foot and ankle infection who were treated with tibial transverse transport combined with antibiotic bone cement between August 2015 and October 2019. There were 22 males and 6 females, with an average age of 65.6 years (range, 41-86 years). There were 25 cases of diabetic foot, 2 cases of arteriosclerosis obliterans, and 1 case of thromboangiitis obliterans. The course of infection ranged from 1 to 27 years, with an average of 14.9 years. The healing condition and time of foot and ankle in all patients were recorded and compared, and the Wagner grading and WIFi (W: lower extremity wound classification; I: ischemic classification; Fi: foot infection classification) grading were compared before and at last follow-up.

Results

The wound surface of 1 diabetic foot patient improved at 111 days after operation, without purulent secretion, and lost follow-up. The remaining 27 cases were followed up 5 to 21 months (mean, 8.4 months). There was no necrosis in the tibial osteotomy incision and the local flap. After operation, 21 cases showed needle reaction of external fixator, but the needle infection gradually improved after the corresponding treatment. Among the 24 patients with diabetic foot, 1 died of multiple organ failure due to pulmonary infection. Acute lower extremity vascular embolism occurred in 1 case, and the foot was amputated due to acute gangrene. In the remaining 22 cases, the wound healing time of foot and ankle was 2.5-11.0 months (mean, 4.6 months). At last follow-up, Wagner grading and WIFi grading of the patients were significantly improved when compared with those before operation ( P<0.05). One patient with thromboangiitis obliterans had foot and ankle healing at 6 months after operation. Two patients with lower extremity arteriosclerosis obliterans had foot and ankle healing at 16 and 18 months after operation, respectively.

Conclusion

Tibial transverse transport combined with the antibiotics embedded bone cement is effective in treating chronic infection of foot and ankle with lower extremity ischemic diseases.

An innovative strategy to treat large metaphyseal segmental femoral bone defect using customized design and 3D printed micro-porous prosthesis: a prospective clinical study

Five patients with segmental irregular-shaped bone defect of the femur were recruited in this study from 2017.12 to 2018.11. All patients were treated by customized design and 3D printed micro-porous prosthesis. And the procedure was divided into stages: radical debridement and temporary fixation (the first stage); the membrane formation and virtual surgery (intervening period for 6-8 weeks); definite reconstruction the defects (the second stage). Routine clinical follow-up and radiographic evaluation were done to assess bone incorporation and complications of internal fixation. The weight-bearing time and the joint function of the patients were recorded. The patients were followed up for an average of 16.4 months. The average length of bone defect and the distal residual bone was 12 cm and 6.5 cm. The average time of partial weight-bearing and full weight-bearing was 12.7 days and 2.6 months. X-ray demonstrated good osseous integration of the implant/bone interface. No complications occurred such as implant loosening, subsidence, loss of correction and infection. At the last follow-up, Harris score of hip joint was excellent in 2 cases, good in 2 cases, fair in 1 case; HSS score of knee joint was good in 4 cases, middle in 1 case. From our study, we concluded that meticulous customized design 3D printed micro-porous prosthesis combined with intramedullary nail may be a promising and an alternative strategy to treat metaphyseal segmental irregular-shaped femoral bone defect, especially for cases with massive juxta-articular bone loss.

Adding a Fibular Strut Allograft to Intramedullary Nail and Cancellous Autograft During Stage II of the Masquelet Technique for Segmental Femur Defects: A Technique Tip

Reconstruction of segmental diaphyseal bone defects has been a major challenge in limb salvage surgery. Staged reconstruction as first described by Masquelet is a common strategy to deal with this problem in limb salvage surgery. One consequence of this technique is a time period of prolonged limited weightbearing while the segmental defect heals. The purpose of this study was to describe an adjunctive technique for stage II of the Masquelet procedure and retrospectively analyze the outcome and weight bearing progression of 3 patients who sustained femur fractures with significant bone loss and underwent this technique. A retrospective chart review was performed. The patients (2 males, 1 female with an average age of 36.6 years) all sustained segmental femur fractures which resulted in significant bone loss. Induced membrane technique with adjunct use of a fibular strut allograft was performed after initial stabilization and PMMA spacer placement. All three patients went on to union and full weight bearing after being treated by the described technique. All the patients were allowed toe-touch weight bearing immediately after surgery and all progressed to weight bearing as tolerated at an average of 3.6 months. Using a fibular strut allograft as an adjunct to the induced membrane technique serves as a biologic and mechanical scaffold and may allow earlier weightbearing.

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.

Application of a pre-filled tissue expander for preventing soft tissue incarceration during tibial distraction osteogenesis

BACKGROUND

Bone transport and distraction osteogenesis has been widely used to treat bone defects after traumatic surgery, but, skin and soft tissue incarceration can be as high as 27.6%.

AIM

To investigate the efficacy of inserting a tissue expander to prevent soft tissue incarceration.

METHODS

Between January 2016 and December 2018, 12 patients underwent implantation of a tissue expander in the subcutaneous layer in the vicinity of a tibial defect to maintain the soft tissue in position. A certain amount of normal saline was injected into the tissue expander during surgery and was then gradually extracted to shrink the expander during the course of transport distraction osteogenesis. The tissue expander was removed when the two ends of the tibial defect were close enough.

RESULTS

In all 12 patients, the expanders remained intact in the subcutaneous layer of the bone defect area during the course of transport distraction osteogenesis. When bone transport was adequate, the expander was removed and the bone transport process was completed. During the whole process, there was no incarceration of skin and soft tissue in the bone defect area. Complications occurred in one patient, who experienced poor wound healing.

CONCLUSION

The pre-filled expander technique can effectively avoid soft tissue incarceration. The authors’ primary success with this method indicates that it may be a valuable tool in the management of incarcerated soft tissue.

Advances in the Masquelet technique: Myeloid-derived suppressor cells promote angiogenesis in PMMA-induced membranes

The periosteum plays a critical role in bone formation and defect reconstruction. The concept of tissue engineering in the periosteum has been suggested to solve the clinical problems related to bone defect repair. Insertion of polymethyl methacrylate (PMMA) bone cement can induce the autologous generation of a tissue-engineered periosteum and has been considered as a promising strategy for bone defect reconstruction. The PMMA-induced membrane is a crucial element in the reconstruction of bone defects, especially for angiogenesis, but its biological mechanism remains elusive. Here, a PMMA-induced membrane model was established using a femoral critically sized defect in mice. We identified myeloid-derived suppressor cells (MDSCs) as a regulatory component of induced membrane vascularization. The increased number of MDSCs was markedly linked to increased membrane thickness and capillary density. Importantly, the results of an in vitro coculture assay indicated that MDSCs of the induced membrane further facilitated the angiogenic capacity of human umbilical vein endothelial cells (HUVECs) by upregulating the expression of VEGFA, Ang2 and HIF-1α. Furthermore, signaling pathway blockade results suggested that STAT3 activation is involved in the upregulation of VEGFA, Ang2 and HIF-1α expression in induced membrane MDSCs. Our findings provide new insights into the mechanism of angiogenesis in the PMMA-induced membrane and confirm the key signaling molecules of MDSCs in induced membrane angiogenesis. Based on these results, this strategy may become a new therapy for the treatment of large bone defects in the future. STATEMENT OF SIGNIFICANCE: In this study, we established an autologous tissue-engineered periosteum - PMMA-induced membrane, which was formed by the foreign body reaction to PMMA bone cement. The induced membrane establishes a blood supply for the large bone defect healing. After investigation, our study discovered the critical cell type in the formation and angiogenesis processes of the induced membrane, myeloid-derived suppressor cells (MDSCs). We revealed that MDSCs of the induced membrane promote the angiogenesis of endothelial cells through the expression of VEGFA, Ang2 and HIF-1α, which was upregulated by the activation of STAT3 signaling. Our findings clarified the beneficial effect of MDSCs in the angiogenesis of bone repair, and offered an additional target for the study of foreign body reactions to bone repair materials.

[Masquelet technique combined with artificial dermis for the treatment of bone and soft tissue defects in rabbits]

Objective

To investigate the effect of Masquelet technique combined with artificial dermis on repairing bone and soft tissue defects in rabbits, and to observe the microstructure and vascularization of induced membrane, so as to guide the clinical treatment of Gustilo-Anderson type Ⅲ open fracture with large bone defect and soft tissue defect.

Methods

Eighty male rabbits, weighing 2.03-2.27 kg (mean, 2.11 kg), were selected. The bilateral thighs of 64 rabbits were randomly divided into experimental group and control group, the remaining 16 rabbits were sham operation group. Bone and soft tissue defect models of femur were made in all rabbits. In the experimental group, the first stage of Masquelet technique was used [polymethyl methacrylate bone cement was filled in bone defect area] combined with artificial dermis treatment; in the control group, the first stage of Masquelet technique was used only; in the sham operation group, the wound was sutured directly without any treatment. Four rabbits in sham operation group and 16 rabbits in the experimental group and control group were sacrificed at 2, 4, 6, and 8 weeks after operation, respectively. The induced membranes and conjunctive membranes were observed on both sides of the femur. The membrane structure was observed by HE staining, and the microvessel density (MVD) was counted by CD34 immunohistochemical staining.

Results

Gross observation showed that the spongy layer of collagen in the artificial dermis of the experimental group disappeared completely at 4 weeks after operation, and the induced membrane structure of the experimental group and the control group was complete; the membrane structure of the control group was translucent, and the membrane structure of the experimental group was thicker, light red opaque, accompanied by small vessel proliferation. The membrane structure of the experimental group and the control group increased gradually from 6 to 8 weeks after operation. In the sham operation group, only scar tissue proliferation was observed over time. HE staining showed that a large number of muscle fibers and a small amount of collagen fibers proliferation with inflammatory cell infiltration could be seen in the experimental group and the control group at 2 weeks after operation; most of the sham operation group were muscle fibers with a small amount of interfibrous vessels. At 4 weeks after operation, collagen fibers increased and some blood vessels formed in the experimental group. The nuclei of collagen fibers in the control group were round-like, while those in the experimental group were flat-round. At 6 and 8 weeks after operation, the collagen fibers in the experimental group and the control group increased. The nuclei of the collagen fibers in the control group were still round-like. The nuclei of the collagen fibers in the experimental group were fusiformis and deeply stained compared with those in the control group. The proliferation of blood vessels was observed in both groups, and the number of proliferation vessels in the experimental group was increased compared with that in the control group. In the sham operation group, a large number of fibroblasts still appeared, but no significant proliferation of blood vessels with time was observed. CD34 immunohistochemical staining showed that MVD in each group increased gradually with the prolongation of time after operation. MVD in the sham operation group was significantly higher than that in the experimental group and the control group at 2 weeks after operation, and significantly smaller than that in the experimental group and the control group at 4, 6, and 8 weeks after operation ( P<0.05). MVD in the experimental group was significantly higher than that in the control group at 4 and 6 weeks after operation ( P<0.05), but there was no significant difference in MVD between the two groups at 2 and 8 weeks ( P>0.05).

Conclusion

Masquelet technique combined with artificial dermis in the treatment of femoral bone defect and soft tissue defect in rabbits can significantly promote the vascularization of membrane structure at 4-6 weeks after operation. The combination of these two methods has guiding significance for the treatment of Gustilo-Anderson type Ⅲ open fracture with bone and soft tissue defects.

Induced membrane maintains its osteogenic properties even when the second stage of Masquelet's technique is performed later

PURPOSE

Previous clinical studies have shown the effectiveness of bone repair using two-stage surgery called the induced membrane (IM) technique. The optimal wait before the second surgery is said to be 1 month. We have been successfully performing the IM technique while waiting an average of 6 months to carry out the second stage. We hypothesised that the IM maintains its beneficial capabilities, even at a later second stage, and that there is no relation between the speed of bone union and the wait between the first and second stage. We sought to explore the biological properties of 'older' IMs sampled to substantiate our clinical observations.

METHODS

Thirty-four patients with a critical size defect were treated with the IM technique. In seven of these patients, pieces of the IM were collected 4.2-14.7 months after the first surgery. IM-derived cell phenotype and osteogenic potential were investigated using in vitro studies (n = 4) while IM nature and function were investigated by histology and immunohistochemistry (n = 3).

RESULTS

The median wait before the second surgery was 5.8 months [range 1.2-14.7] and bone healing occurred at 7.6 months [range 2.5-49.9] for 26 patients. IMs aged 4.2-14.7 months contained mesenchymal stromal cells with in vitro osteogenic potential and corresponded to a multipotent tissue with osteogenic and chondrogenic capabilities contributing to osteogenesis over time.

CONCLUSION

This preliminary study suggests the IM retains its powerful osteogenic properties over time and that waiting longer between the two surgeries does not delay bone union.

Reconstruction of large segmental bone defects in rabbit using the Masquelet technique with α-calcium sulfate hemihydrate

Background

Large segmental bone defects can be repaired using the Masquelet technique in conjunction with autologous cancellous bone (ACB). However, ACB harvesting is severely restricted. α-calcium sulfate hemihydrate (α-CSH) is an outstanding bone substitute due to its easy availability, excellent biocompatibility, biodegradability, and osteoconductivity. However, the resorption rate of α-CSH is too fast to match the rate of new bone formation. The objective of this study was to investigate the bone repair capacity of the Masquelet technique in conjunction with isolated α-CSH or an α-CSH/ACB mix in a rabbit critical-sized defect model.

Methods

The rabbits (n = 28) were randomized into four groups: sham, isolated α-CSH, α-CSH/ACB mix, and isolated ACB group. A 15-mm critical-sized defect was established in the left radius, followed by filling with polymethyl methacrylate spacer. Six weeks after the first operation, the spacers were removed and the membranous tubes were grafted with isolated α-CSH, isolated ACB, α-CSH/ACB mix, or none. Twelve weeks later, the outcomes were evaluated by manual assessment, radiography, and spiral-CT. The histopathological and morphological changes were examined by H&E staining. The levels of alkaline phosphatase and osteocalcin were analyzed by immunohistochemistry and immunofluorescence staining.

Results

Our results suggest that the bone repair capacity of the α-CSH/ACB mix group was similar to the isolated ACB group, while the isolated α-CSH group was significantly decreased compared to the isolated ACB group.

Conclusion

These results highlighted a promising strategy in the healing of large segmental bone defect with the Masquelet technique in conjunction with an α-CSH/ACB mix (1:1, w/w) as they possessed the combined effects of sufficient supply and low resorption.

Masquelet Reconstruction for Posttraumatic Segmental Bone Defects in the Forearm

PURPOSE

The Masquelet technique is a procedure increasingly utilized for addressing segmental bone defects. The technique involves staged procedures consisting of bone debridement and temporary spacer placement to induce membrane formation, followed by delayed bone grafting. This report summarizes our center's experience with the Masquelet technique to reconstruct bone loss exclusively in the forearm.

METHODS

We reviewed all cases in which the Masquelet technique was used to reconstruct segmental bone defects in the forearm resulting from acute trauma or nonunion, with or without infection, between 2014 and 2017 at a level-1 trauma center. Injury mechanism, prior surgeries, extent of bone defect, and demographic data were collected. Union was assessed along with treatment-related complications or reoperations.

RESULTS

We identified 9 patients with segmental bony defects in the forearm treated with the Masquelet technique. Among this cohort, 5 patients had bone defects associated with acute open fractures and 4 patients presented with nonunion (1 atrophic and 3 infected nonunions). The median bony defect was 4.7 cm (range, 1.7-5.4 cm) at the time of grafting. Second stage grafting was performed with Reamer Irrigator Aspirator autograft from the femur in 8 patients and iliac crest bone cancellous graft in 1 patient. Union was achieved in all 9 patients. Six patients achieved union by 3-month follow-up, 2 patients by 6 months, and 1 patient by 12 months. One patient required a reoperation for plate fracture prior to union treated with revision internal fixation and grafting.

CONCLUSIONS

The Masquelet technique effectively reconstructed traumatic and posttraumatic segmental defects in the forearm with a low incidence of complication.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic V.

Masquelet Technique: Effects of Spacer Material and Micro-topography on Factor Expression and Bone Regeneration

We and others have shown that changing surface characteristics of the spacer implanted during the first Masquelet stage alters some aspects of membrane development. Previously we demonstrated that titanium (TI) spacers create membranes that are better barriers to movement of solutes > 70 kDa in size than polymethyl methacrylate (PMMA) induced-membranes, and roughening creates more mechanically compliant membranes. However, it is unclear if these alterations affect the membrane's biochemical environment or bone regeneration during the second stage. Ten-week-old, male Sprague-Dawley rats underwent an initial surgery to create an externally stabilized 6 mm femoral defect. PMMA or TI spacers with smooth (~ 1 μm) or roughened (~ 8 μm) surfaces were implanted. Four weeks later, rats were either euthanized for membrane harvest or underwent the second Masquelet surgery. TI spacers induced thicker membranes that were similar in structure and biochemical expression. All membranes were bilayered with the inner layer having increased factor expression [bone morphogenetic protein 2 (BMP2), transforming growth factor beta (TGFβ), interleukin 6 (IL6), and vascular endothelial growth factor (VEGF)]. Roughening increased overall IL6 levels. Ten-weeks post-engraftment, PMMA-smooth induced membranes better supported bone regeneration (60% union). The other groups only had 1 or 2 that united (9-22%). There were no significant differences in any micro computed tomography or dynamic histology outcome. In conclusion, this study suggests that the membrane's important function in the Masquelet technique is not simply as a barrier. There is likely a critical biochemical, cellular, or vascular component as well.

Preclinical induced membrane model to evaluate synthetic implants for healing critical bone defects without autograft

Critical bone defects pose a formidable orthopaedic problem in patients with bone loss. We developed a preclinical model based on the induced membrane technique using a synthetic graft to replace autograft for healing critical bone defects. Additionally, we used a novel osteoconductive scaffold coupled with a synthetic membrane to evaluate the potential for single-stage bone regeneration. Three experimental conditions were investigated in critical femoral defects in rats. Group A underwent a two-stage procedure with insertion of a polymethylmethacrylate (PMMA) spacer followed by replacement with a 3D printed polycaprolactone(PCL)/β-tricalcium phosphate (β-TCP) osteoconductive scaffold after 4 weeks. Group B received a single-stage PCL/β-TCP scaffold wrapped in a PCL-based microporous polymer film creating a synthetic membrane. Group C received a single-stage bare PCL/β-TCP scaffold. All groups were examined by serial radiographs for callus formation. After 12 weeks, the femurs were explanted and analyzed with micro-CT and histology. Mean callus scores tended to be higher in Group A. Group A showed statistically significant greater bone formation on micro-CT compared with other groups, although bone volume fraction was similar between groups. Histology results suggested extensive bone ingrowth and new bone formation within the macroporous scaffolds in all groups and cell infiltration into the microporous synthetic membrane. This study supports the use of a critical size femoral defect in rats as a suitable model for investigating modifications to the induced membrane technique without autograft harvest. Future investigations should focus on bioactive synthetic membranes coupled with growth factors for single-stage bone healing. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.