Altering spacer material affects bone regeneration in the Masquelet technique in a rat femoral defect

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.

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

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

Biodegradable poly(caprolactone fumarate) 3D printed scaffolds for segmental bone defects within the Masquelet technique

Segmental bone defects, often clinically treated with nondegradable poly(methylmethacrylate) (PMMA) in multistage surgeries, present a significant clinical challenge. Our study investigated the efficacy of 3D printed biodegradable polycaprolactone fumarate (PCLF)/PCL spacers in a one-stage surgical intervention for these defects, focusing on early bone regeneration influenced by spacer porosities. We compared nonporous PCLF/PCL and PMMA spacers, conventionally molded into cylinders, with porous PCLF/PCL spacers, 3D printed to structurally mimic segmental defects in rat femurs for a 4-week implantation study. Histological analysis, including tissue staining and immunohistochemistry with bone-specific antibodies, was conducted for histomorphometry evaluation. The PCLF/PCL spacers demonstrated compressive properties within 6 ± 0.5 MPa (strength) and 140 ± 15 MPa (modulus). Both porous PCLF/PCL and Nonporous PMMA formed collagen-rich membranes (PCLF/PCL: 92% ± 1.3%, PMMA: 86% ± 1.5%) similar to those induced in the Masquelet technique, indicating PCLF/PCL's potential for one-stage healing. Immunohistochemistry confirmed biomarkers for tissue regeneration, underscoring PCLF/PCL's regenerative capabilities. This research highlights PCLF/PCL scaffolds' ability to induce membrane formation in critical-sized segmental bone defects, supporting their use in one-stage surgery. Both solid and porous PCLF/PCL spacers showed adequate compressive properties, with the porous variants exhibiting BMP-2 expression and woven bone formation, akin to clinical standard PMMA. Notably, the early ossification of the membrane into the pores of porous scaffolds suggests potential for bone interlocking and regeneration, potentially eliminating the need for a second surgery required for PMMA spacers. The biocompatibility and biodegradability of PCLF/PCL make them promising alternatives for treating critical bone defects, especially in vulnerable patient groups.

[Biological reconstruction of large bone defects : Masquelet technique and new procedures]

Extensive diaphyseal and metaphyseal bone defects continue to pose a major challenge for orthopedic trauma surgeons. Various treatment options have been described for the biological reconstruction of these defects. The most frequently used methods are bone segment transport, the Masquelet technique and 3D printed scaffolds. As far as the Masquelet technique is concerned, in the first stage spacers, such as polymethyl methacrylate (PMMA), calcium sulfate or polypropylene are inserted into the bone defects to induce a foreign body membrane. In the second stage the bone defect surrounded by the induced membrane is filled with autologous cancellous bone. The time interval between the first and second interventions is usually 4-8 weeks whereby the induced membranes do not lose their bioactivity even with a latency period longer than 8 weeks. Three-dimensional printed scaffolds are increasingly used but large clinical studies are lacking in order to show the exact role of this procedure in the reconstruction of bone defects.

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.

Puricelli biconvex arthroplasty as an alternative for temporomandibular joint reconstruction: description of the technique and long-term case report

Background

There are several indications for partial or total replacement of the temporomandibular joint (TMJ), including neoplasms and severe bone resorptions. In this regard, several techniques have been suggested to increase the functionality and longevity of these prosthetic devices. This case report describes the treatment of a TMJ ankylosis patient with the Puricelli biconvex arthroplasty (ABiP) technique, with a long-term follow-up.

Case presentation

In 1978, a 33-year-old male polytraumatised patient developed painful symptoms in the right preauricular region, associated with restricted movement of the ipsilateral TMJ. Due to subcondylar fracture, an elastic maxillomandibular immobilisation (EMMI) was applied. Subsequently, the patient was referred for treatment when limitations of the interincisal opening (10 mm) and the presence of spontaneous pain that increased on palpation were confirmed. Imaging exams confirmed the fracture, with anteromedial displacement and bony ankylosis of the joint. Exeresis of the compromised tissues and their replacement through ABiP was indicated. The method uses conservative access (i.e., preauricular incision), partial resection of the ankylosed mass, and tissue replacement using two poly(methyl methacrylate) components, with minimal and stable contact between the convex surfaces. At the end of the procedure, joint stability and dental occlusion were tested. The patient showed significant improvement at the postoperative 6-month follow-up, with no pain and increased mouth opening range (30 mm). At the 43-year follow-up, no joint noises, pain or movement restrictions were reported (mouth opening of 36 mm). Imaging exams did not indicate tissue degeneration and showed the integrity of prosthetic components.

Conclusions

The present case report indicates that ABiP enables joint movements of the TMJ, allowing the remission of signs and symptoms over more than 40 years of follow-up. These data suggest that this technique is a simple and effective alternative when there is an indication for TMJ reconstruction in adult patients with ankylosis.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Probing the role of methyl methacrylate release from spacer materials in induced membrane bone healing

In the induced membrane (IM) technique for bone reconstruction, a poly(methyl methacrylate) (PMMA) spacer is implanted to induce formation of a foreign body membrane around the defect site. Membrane development is essential for later bone grafting success, yet the mechanism by which the IM promotes bone regeneration remains unknown, as are the ways that spacer composition plays a role in the membrane's healing potential. This study investigated the impact of leached methyl methacrylate (MMA)-the major monomeric component of PMMA-on IM development. In vitro cell culture found that MMA elution did not impact endothelial cell or mesenchymal stem cell proliferation. For in vivo analysis, we advanced a streamlined rat femoral model to efficiently study the influence of spacer properties on IM characteristics. Comparison of membrane formation around polycaprolactone (PCL), MMA-eluting PCL (high-dose PCL-MMA and low-dose PCL-MMA), and surgical PMMA revealed robust membranes enveloped all groups after 4 weeks in vivo, with elevated expression of osteogenic bone morphogenetic protein-2 and angiogenic vascular endothelial growth factor compared with the surrounding muscle and bone tissues. Growth factor quantitation in IM tissue found no statistically significant difference between groups. New bone growth, vascularization, and CD163+ macrophage populations surrounding the polymer implants were also quantified; and blood vessel formation around high-dose PCL-MMA was found to be significantly decreased compared with PCL alone. To the best of our knowledge, these findings represent the first time that results have been obtained about the characteristics of membranes formed around PCL in the IM setting.

Effects of PMMA spacer loaded with varying vancomycin concentrations on bone regeneration in the Masquelet technique

Whether antibiotics should be included remains greatly debated in Masquelet technique. This study intended to determine the effect of polymethyl methacrylate (PMMA) spacer loaded with different vancomycin concentrations on bone defect repair. Hollow cylindrical spacers consisting of PMMA and varying vancomycin concentrations (0, 1, 2, 4, 6, 8, and 10 g) were prepared. Critical bone defects of rabbits were created at the radial shaft, and spacers were implanted and subsequently intramedullary fixed with retrograde Kirschner’s wires (n = 4 for each vancomycin concentration). After 4 weeks, the induced membranes were opened and cancellous allografts were implanted into the defects. Eight weeks post-operatively, the results of X-ray, histology, and micro-CT revealed that some cortical bone was formed to bridge the gap and the bone marrow cavity was formed over time. Quantitatively, there was more new bone formation in the groups with a relatively lower vancomycin concentration (1–4 g) compared with that in the groups with a higher vancomycin concentration (6–10 g). Our findings suggested that PMMA spacers loaded with relatively lower vancomycin concentrations (1–4 g) did not interfere with new bone formation, whereas spacers loaded with relatively higher vancomycin concentrations (6–10 g) had negative effects on bone formation.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The induced membrane technique in animal models: a systematic review

Objectives:

Data Sources:

Study Selection:

Data Extraction:

Data Synthesis:

Conclusions:

Reconstruction of Ipsilateral Femoral and Tibial Bone Defect by 3D Printed Porous Scaffold Without Bone Graft: A Case Report

CASE

This study reported the case of a 42-year-old woman with traumatic ipsilateral critical bone defect of right femur and tibia after a motor accident. Three-dimensional (3D) printed porous titanium scaffolds were innovatively used to reconstruct this challenging situation. The initial stability was safe enough for early exercise and partial weight bearing. The 26-month follow-up showed osseous integration of the prosthesis-bone interface with short-term satisfactory clinical result.

CONCLUSION

The custom-designed 3D-printed porous scaffold has the potential to become an effective option for reconstructing the segmental irregular-shaped bone defect.

Regenerative Approaches for the Treatment of Large Bone Defects

A variety of engineered materials have gained acceptance in orthopedic practice as substitutes for autologous bone grafts, although the regenerative efficacy of these engineered grafts is still limited compared with that of transplanted native tissues. For bone defects greater than 4-5 cm, however, common bone grafting procedures are insufficient and more complicated surgical interventions are required to repair and regenerate the damaged or missing bone. In this review, we describe current grafting materials and surgical techniques for the reconstruction of large bone defects, followed by tissue engineering (TE) efforts to develop improved therapies. Particular emphasis is placed on graft vascularization, because for both autologous bone and engineered alternatives, achieving adequate vascular development within the regenerating bone tissues remains a significant challenge in the context of large bone defects. To this end, TE and surgical strategies to induce development of a vasculature within bone grafts are discussed. Impact statement This review aims to present an accessible and thorough overview of current orthopedic surgical techniques as well as bone tissue engineering and vascularization strategies that might one day offer improvements to clinical therapies for the repair of large bone defects. We consider the lessons that clinical orthopedic reconstructive practices can contribute to the push toward engineered bone.

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.

Sexual differences in bone porosity, osteocyte density, and extracellular matrix organization due to osteoblastic-specific Bmp2 deficiency in mice

Clinical studies have come to conflicting conclusions regarding BMP2 deficiency's link to regulating bone mass and increasing fracture risk. This may be due to the signaling protein having sex- or age-dependent effects. Previous pre-clinical studies have supported a role, but have not adequately determined the physical mechanism causing altered bulk material properties. This study investigated the physical effects of Bmp2 ablation from osteogenic lineage cells (Osx-Cre; Bmp2^fl/fl) in 10- and 15-week-old male and female mice. Bones collected post-mortem were subjected to fracture toughness testing, reference point indentation testing, microCT, and histological analysis to determine the multi-scale relationships between mechanical/material behavior and collagen production, collagen organization, and bone architecture. BMP2-deficient bones were smaller, more brittle, and contained more lacunae-scale voids and cortical pores. The cellular density was significantly increased and there were material-level differences measured by reference point indentation, independently of collagen fiber alignment or organization. The disparities in bone size and in bone fracture toughness between genotypes were especially striking in males at 15-weeks-old. Together, this study suggests that there are sex- and age-dependent effects of BMP2 deficiency. The results from both sexes also warrant further investigation into BMP2 deficiency's role in osteoblasts' transition to osteocytes and overall bone porosity.

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

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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.

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

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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.

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.

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.

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.

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.

From two stages to one: acceleration of the induced membrane (Masquelet) technique using human acellular dermis for the treatment of non-infectious large bone defects

Introduction

The induced membrane technique for the treatment of large bone defects is a two-step procedure. In the first operation, a foreign body membrane is induced around a spacer, then, in the second step, several weeks or months later, the spacer is removed and the Membrane pocket is filled with autologous bone material. Induction of a functional biological membrane might be avoided by initially using a biological membrane. In this study, the effect of a human acellular dermis (hADM, Epiflex, DIZG gGmbH) was evaluated for the treatment of a large (5 mm), plate-stabilised femoral bone defect.

Material and Methods

In an established rat model, hADM was compared to the two-stage induced membrane technique and a bone defect without membrane cover. Syngeneous spongiosa from donor animals was used for defect filling in all groups. The group size in each case was n = 5, the induction time of the membrane was 3–4 weeks and the healing time after filling of the defect was 8 weeks.

Results

The ultimate loads were increased to levels comparable with native bone in both membrane groups (hADM: 63.2% ± 29.6% of the reference bone, p < 0.05 vs. no membrane, induced membrane: 52.1% ± 25.8% of the reference bone, p < 0.05 vs. no membrane) and were significantly higher than the control group without membrane (21.5%). The membrane groups were radiologically and histologically almost completely bridged by new bone formation, in contrast to the control Group where no closed osseous bridging could be observed.

Conclusion

The use of the human acellular dermis leads to equivalent healing results in comparison to the two-stage induced membrane technique. This could lead to a shortened therapy duration of large bone defects.

Comparison between the induced membrane technique and distraction osteogenesis in treating segmental bone defects: An experimental study in a rat model

Previous studies have suggested that treatment plans for segmental bone defects (SBDs) are affected by the bone defect sizes. If the selected treatment was not the most appropriate, it would not contribute to bone healing, but increase complications. The induced membrane technique (IM) and distraction osteogenesis (DO) have been proved to be effective in treating SBDs. However, the differences between the two in therapeutic effects on SBDs with different sizes are still unclear. Thus, we aimed to observe the effects of IM and DO on different sizes of SBDs and to further determine what method is more appropriate for what defect size. Rat models of 4-, 6-and 8-mm mid-diaphyseal defects using IM and DO techniques were established. X-rays, micro-CT, histological and immunohistochemical examinations were performed to assess bone repair. Faster bone formation rate, shorter treatment duration, higher expressions of OPN and OCN and higher parameters of bone properties including bone mineral density (BMD), bone volume/total tissue volume (BV/TV), mineral apposition rate (MAR) and mineral surface/bone surface (MS/BS) were found in 4-mm SBDs treated with DO than in those with IM treatment. However, the results were reversed and IM outperformed DO in bone repair capacity for 8-mm SBDs, while no significant difference emerges in the case of 6-mm SBDs. This study suggests that the therapeutic effects of IM and DO may be subjected to sizes of bone defects and the best treatment size of defects is different between the two. For small-sized SBDs, DO may be more suitable and efficient than IM, but IM has advantages over DO for over-sized SBDs, while DO and IM show similar bone repair capability in moderate-sized SBDs, which would offer a new insight into how to choose DO and IM for SBDs in clinical practice and provide references for further clinical research.

Intervertebral Bridging Ossification After Percutaneous Kyphoplasty in Osteoporotic Vertebral Compression Fractures

BACKGROUND

Percutaneous kyphoplasty (PKP) is effective in treating osteoporotic vertebral compression fractures (OVCFs). Intervertebral bridging ossification can sometimes be detected after surgery, but studies related to its formation mechanism and its influence on outcome are few.

CASE DESCRIPTION

We reviewed patients' radiologic images and found 7 patients in whom intervertebral bridging ossification developed after PKP. Their personal and clinical information was recorded. The 7 patients had an average age of 63.43 ± 4.79 years. Injured levels included L1 (1 patients) and L2 (1 patient). GeneX and PMMA cement were respectively applied. Both the Cobb angle and the VAS scores were significantly improved after surgery, but all surgical vertebrae showed recollapse combined with larger Cobb angle at the last follow-up visits. In 1 patient the new-onset T11 fracture developed 29 months after surgery.

CONCLUSIONS

We deemed that spinal degeneration, mechanical instability, bone cement, and fracture pattern are all potential promoting factors for intervertebral bridging ossification. Solid bridging ossification may increase local spinal stability, but it also increases the risk of adjacent vertebral fractures.

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.