Induced membrane technique: Advances in the management of bone defects

Bone marrow fluid enhances the osteogenic activity of induced membrane leading to spontaneous osteogenesis: experimental validation and application in tibiofibular fusion for support reconstruction of segmental tibial defects

BACKGROUND

Managing large bone defects remains a significant clinical problem. We enhanced the osteogenic activity of the induced membrane (IM) by incorporating bone marrow fluid, leading to spontaneous osteogenesis (SO). We aimed to explore the application of this method in tibiofibular fusion (TFF) for reconstructing segmental tibial defects.

METHODS

Forty-two rats with femoral defects were divided into seven groups (n = 6). Defects in groups A1-3 and B1-3 were filled with polymethylmethacrylate spacers while Group B4 was the control. Kirschner wires were used in Groups A1 and B1, plating was used in Groups A3 and B3-4, while the medullary canal was sealed in Groups A2 and B2. In Group A, osteogenic activity was measured using immunohistochemistry, W-B, and qRT-PCR. In Group B, the osteogenic results were measured using X-ray and gross examinations. Ten patients with 4-10 cm segmental defects of the middle and distal tibia underwent reconstruction using the IM technique, and IM and bone marrow fluid-induced SO for TFF, whose effects were assessed.

RESULTS

At five weeks, Group A1 showed higher levels of BMSCs and expression of BMP-2 and TGF-β1 than Groups A2 and A3 (p < 0.05). After 12 weeks, Group B1 had more new bone at the bone end than Group B3 (p = 0.009) whereas Groups B2 and B4 did not. All tibial defects and TFF healed. The TFF site and posterior tibia healed faster than the other sides and showed quicker clinical healing (p < 0.05). All patients could fully bear weight before tibial clinical healing, with an excellent-to-good functional rate of 80% (Paley's criterion) at the 13 - to 36-month follow-up.

CONCLUSION

Bone marrow fluid enhances the osteogenic activity of IMs leading to SO. TFF by SO progresses faster than tibial clinical healing, making the IM technique an effective stabilizer for faster and better functional recovery after reconstruction of segmental defects of the middle and distal tibia.

Lyophilized apoptotic vesicles improve hemostasis and bone regeneration in traumatic patients with impacted third molar extraction

Uncontrollable bleeding and tissue defects caused by trauma are significant clinical issues. Apoptotic vesicles (apoVs) derived from mesenchymal stem cells (MSCs) have shown promise for hemostasis and tissue regeneration, but their clinical safety and efficacy remain unverified. We investigated the procoagulant and regenerative function of lyophilized MSC-derived apoVs (MSC-apoVs) using in vitro experiments and in vivo rat models. In addition, we conducted a double-blind, randomized, self-controlled clinical trial to evaluate the safety and efficiency of lyophilized MSC-apoVs for hemostasis and bone regeneration following extraction of impacted mandibular third molars. We show that lyophilized MSC-apoVs maintain their procoagulant and regenerative functions after storage at 4°C for 3 months and upregulate tripartite motif containing 71 to activate the extracellular signal-regulated kinase signaling pathway. Furthermore, among the 43 enrolled subjects, 39 patients completed all follow-ups and 4 patients were lost to contact. All 39 patients tolerated MSC-apoVs well, with no serious adverse events or abnormal blood test results observed. The MSC-apoV group exhibited shortened hemostatic time and accelerated alveolar bone regeneration compared with the control group. This is the first clinical study to demonstrate that apoVs are safe, well tolerated, and effective as a cell-free biological therapy for hemostasis and bone regeneration.

Comparison of free vascularized fibular grafts and the Masquelet technique for the treatment of segmental bone defects with open forearm fractures: a retrospective cohort study

PURPOSE

Severe open forearm fractures commonly involve segmental bone defects. Although several methods have been proposed to treat segmental bone defects with such fractures, research comparing the radiological and clinical outcomes of free vascularized fibular grafts (FVFG) and the Masquelet technique (MT) is rare.

METHODS

Data on 43 patients with open forearm fractures and segmental bone defects treated surgically in our hospital from January 2005 to January 2021 were retrospectively analyzed, and these patients were divided into an FVFG group (18 cases) and an MT group (25 cases). Clinical and radiological evaluations were performed regularly, and the minimum follow-up was 18 months.

RESULTS

All 43 patients were followed up for 18 to 190 months, with a mean of 46.93 months. The mean follow-up time was significantly longer in the FVFG group than in the MT group (p = 0.000). Bone healing time was 3-16 months, with a mean of 4.67 months. The QuickDASH score at the last follow-up was 0-38.6, with a mean of 17.71, and there was no statistically significant difference between the two groups. Operative time, hospital stay, and intraoperative bleeding for bone defect reconstruction were higher in the FVFG group compared to the MT group (p = 0.000), whereas the number of procedures was lower in the FVFG group than in the MT group (p = 0.035).

CONCLUSIONS

FVFG and the MT showed satisfactory clinical results for segmental bone defects of the forearm. Compared with FVFG, the MT exhibited a lower operative time, hospital stay, and intraoperative bleeding.

LEVEL OF EVIDENCE

Level IV. Trial registration This study was registered in the Chinese Clinical Trial Registry (registration no. ChiCTR2300067675; registered 17 January 2023), https://www.chictr.org.cn/showproj.html?proj=189458 .

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

The induced membrane technique for the management of infected segmental bone defects

Aims

The aim of the present study was to assess the outcomes of the induced membrane technique (IMT) for the management of infected segmental bone defects, and to analyze predictive factors associated with unfavourable outcomes.

Methods

Between May 2012 and December 2020, 203 patients with infected segmental bone defects treated with the IMT were enrolled. The digital medical records of these patients were retrospectively analyzed. Factors associated with unfavourable outcomes were identified through logistic regression analysis.

Results

Among the 203 enrolled patients, infection recurred in 27 patients (13.3%) after bone grafting. The union rate was 75.9% (154 patients) after second-stage surgery without additional procedures, and final union was achieved in 173 patients (85.2%) after second-stage surgery with or without additional procedures. The mean healing time was 9.3 months (3 to 37). Multivariate logistic regression analysis of 203 patients showed that the number (≥ two) of debridements (first stage) was an independent risk factor for infection recurrence and nonunion. Larger defect sizes were associated with higher odds of nonunion. After excluding 27 patients with infection recurrence, multivariate analysis of the remaining 176 patients suggested that intramedullary nail plus plate internal fixation, smoking, and an allograft-to-autograft ratio exceeding 1:3 adversely affected healing time.

Conclusion

The IMT is an effective method to achieve infection eradication and union in the management of infected segmental bone defects. Our study identified several risk factors associated with unfavourable outcomes. Some of these factors are modifiable, and the risk of adverse outcomes can be reduced by adopting targeted interventions or strategies. Surgeons can fully inform patients with non-modifiable risk factors preoperatively, and may even use other methods for bone defect reconstruction.

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.

Case report: A left forearm mass with eccentric intramedullary ulnar destruction diagnosed as alveolar rhabdomyosarcoma and treated by wide resection and free vascularized fibular graft

Background

Alveolar Rhabdomyosarcoma is a profoundly malignant soft-tissue sarcoma that predominantly affects children and adolescents. However, the medical field lacks consensus regarding the optimal surgical approach to be undertaken in cases where this tumor causes local bone destruction in the upper limb.

Case description

A 17-year-old male presented a mass in his left forearm and CT and MRI indicated that the mass had penetrated the ulnar cortex and infiltrating the medulla, resulting in the formation of an eccentric trans-ventricular tumor focus. The sizable tumor affected the volar muscles of the forearm as well as the ulnar bone marrow, exerting pressure on the ulnar artery and vein. It was confirmed by needle biopsy that the mass is alveolar rhabdomyosarcoma. Following two courses of neoadjuvant chemotherapy, the tumor was widely excised en bloc. Autologous fibula with a vascular pedicle was utilized for reconstruction during the procedure. In the postoperative follow-up, no local recurrence of the tumor was observed. Furthermore, the patient retained satisfactory wrist flexion and pronation function in the left forearm.

Conclusions

Alveolar rhabdomyosarcoma is an uncommon and highly aggressive form of soft tissue sarcoma. Scientific management necessitates a multidisciplinary approach, combining chemotherapy with surgery. In cases where the tumor invaded into compartment of the bone, careful consideration should be given to the boundaries of tumor resection, the extent of osteotomy, and the approach to musculoskeletal reconstruction when designing the surgical plan. Through reporting our own case and thoroughly reviewing previous clinical experiences, we aim to provide valuable insights for the treatment of this particular disease.

Application of double plate fixation combined with Masquelet technique for large segmental bone defects of distal tibia: a retrospective study and literature review

BACKGROUND

There is no effective consensus on the choice of internal fixation method for the Masquelet technique in the treatment of large segmental bone defects of the distal tibia. Thus, the study aimed to investigate the outcomes of the Masquelet technique combined with double plate fixation in the treatment of large segmental bone defects.

METHODS

This was a retrospective study involving 21 patients with large segmental bone defects of the distal tibia who were treated between June 2017 and June 2020. The length of bone defect ranged from 6.0 cm to 11 cm (mean, 8.19 cm). In the first stage of treatment, following complete debridement, a cement spacer was placed to induce membrane formation. In the second stage, double plate fixation and autologous cancellous bone grafting were employed for bone reconstruction. Each patient's full weight-bearing time, bone healing time, and Iowa ankle score were recorded, and the occurrence of any complications was noted.

RESULTS

All patients were followed up for 16 to 26 months (mean, 19.48 months). The group mean full weight-bearing time and bone healing time after bone grafting were 2.41 (± 0.37) months and 6.29 (± 0.66) months, respectively. During the treatment, one patient had a wound infection on the medial side of the leg, so the medial plate was removed. The wound completely healed after debridement without any recurrence. After extraction of iliac bone for grafting, one patient had a severe iliac bone defect, which was managed by filling the gap with a cement spacer. Most patients reported mild pain in the left bone extraction area after surgery. The postoperative Iowa ankle score range was 84-94 (P < 0.05). In this cohort, 15 cases were rated as "excellent", and 6 cases as "good" on the Iowa ankle scoring system.

CONCLUSION

The Masquelet technique combined with double plate fixation is a safe and effective method for the treatment of large segmental bone defects of the distal tibia.

Orthoplastic limb reconstruction using free fibula flap after trauma: Outcomes from a retrospective European multicenter study

BACKGROUND

Free vascularized fibula flap represents the gold standard vascularized bone graft for the management of segmental long bone defects after traumatic injury. The current study represents the largest retrospective multicenter data collection on the use of free fibula flap (FFF) for extremities' orthoplastic reconstruction after trauma aiming to highlight current surgical practice and to set the basis for updating current surgical indications.

METHODS

The study is designed as a retrospective analysis of prospectively collected data between 2009 and 2021 from six European University hospitals. Patients who underwent fibula flap reconstruction after acute traumatic injury (AF) or as a late reconstruction (LF) after post-traumatic non-union of upper or lower limb were included. Only extra-articular, diaphyseal fracture were included in the study. Surgical data were collected. Time to bone healing and complications were reported as clinical outcomes.

RESULTS

Sixty-two patients were included in the study (27 in the AF group and 35 in the LF group). The average patients' age at the time of the traumatic event was 45.3 ± 2.9 years in the AF group and 41.1 ± 2.1 years in the LF group. Mean bone defect size was 7.7 ± 0.6 cm for upper limb and 11.2 ± 1.1 cm (p = .32) for lower limb. Bone healing was uneventful in 69% of treated patients, reaching 92% after complementary procedures. Bone healing time was 7.6 ± 1.2 months in the acute group and 9.6 ± 1.5 months in the late group. An overall complication rate of 30.6% was observed, with a higher percentage of late bone complications in the LF group (34%), mostly non-union cases.

CONCLUSIONS

FFF reconstruction represents a reliable and definitive solution for long bone defects with bone healing reached in 92% cases with a 8.4 months of average bone healing time.

Irisin-loaded electrospun core-shell nanofibers as calvarial periosteum accelerate vascularized bone regeneration by activating the mitochondrial SIRT3 pathway

The scarcity of native periosteum poses a significant clinical barrier in the repair of critical-sized bone defects. The challenge of enhancing regenerative potential in bone healing is further compounded by oxidative stress at the fracture site. However, the introduction of artificial periosteum has demonstrated its ability to promote bone regeneration through the provision of appropriate mechanical support and controlled release of pro-osteogenic factors. In this study, a poly (l-lactic acid) (PLLA)/hyaluronic acid (HA)-based nanofibrous membrane was fabricated using the coaxial electrospinning technique. The incorporation of irisin into the core-shell structure of PLLA/HA nanofibers (PLLA/HA@Irisin) achieved its sustained release. In vitro experiments demonstrated that the PLLA/HA@Irisin membranes exhibited favorable biocompatibility. The osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) was improved by PLLA/HA@Irisin, as evidenced by a significant increase in alkaline phosphatase activity and matrix mineralization. Mechanistically, PLLA/HA@Irisin significantly enhanced the mitochondrial function of BMMSCs via the activation of the sirtuin 3 antioxidant pathway. To assess the therapeutic effectiveness, PLLA/HA@Irisin membranes were implanted in situ into critical-sized calvarial defects in rats. The results at 4 and 8 weeks post-surgery indicated that the implantation of PLLA/HA@Irisin exhibited superior efficacy in promoting vascularized bone formation, as demonstrated by the enhancement of bone matrix synthesis and the development of new blood vessels. The results of our study indicate that the electrospun PLLA/HA@Irisin nanofibers possess characteristics of a biomimetic periosteum, showing potential for effectively treating critical-sized bone defects by improving the mitochondrial function and maintaining redox homeostasis of BMMSCs.

Treatment of infected bone defects with the induced membrane technique

Aims

This study aimed to evaluate the effectiveness of the induced membrane technique for treating infected bone defects, and to explore the factors that might affect patient outcomes.

Methods

A comprehensive search was performed in PubMed, Embase, and the Cochrane Central Register of Controlled Trials databases between 1 January 2000 and 31 October 2021. Studies with a minimum sample size of five patients with infected bone defects treated with the induced membrane technique were included. Factors associated with nonunion, infection recurrence, and additional procedures were identified using logistic regression analysis on individual patient data.

Results

After the screening, 44 studies were included with 1,079 patients and 1,083 segments of infected bone defects treated with the induced membrane technique. The mean defect size was 6.8 cm (0.5 to 30). After the index second stage procedure, 85% (797/942) of segments achieved union, and 92% (999/1,083) of segments achieved final healing. The multivariate analysis with data from 296 patients suggested that older age was associated with higher nonunion risk. Patients with external fixation in the second stage had a significantly higher risk of developing nonunion, increasing the need for additional procedures. The autografts harvested from the femur reamer-irrigator-aspirator increased nonunion, infection recurrence, and additional procedure rates.

Conclusion

The induced membrane technique is an effective technique for treating infected bone defects. Internal fixation during the second stage might effectively promote bone healing and reduce additional procedures without increasing infection recurrence. Future studies should standardize individual patient data prospectively to facilitate research on the affected patient outcomes.

A review of the Masquelet technique in the treatment of lower limb critical-size bone defects

The need for bone tissue to heal effectively is paramount given its role in the mechanical support of tissues. Bone has a very good natural healing potential in comparison with most other tissue types, largely regenerating to its pre-injury state in the vast majority of cases. Certain factors such as high energy trauma, tumour resection, revision surgery, developmental deformities and infection can lead to the formation of bone defects, where the intrinsic healing potential of bone is diminished owing to bone loss. Various approaches to resolving bone defects exist in current practice, each with their respective benefits and drawbacks. These include bone grafting, free tissue transfer, Ilizarov bone transport and the Masquelet induced membrane technique. This review focuses on evaluating the Masquelet technique, discussing its method and underlying mechanisms, the effectiveness of certain modifications, and its potential future directions.

Orthoplastic management of distal tibia bone infection using Masquelet technique and PRECICE nail: A case report

The orthoplastic treatment of post-traumatic bone infections is complex and requires a multidisciplinary approach using both orthopedic and plastic surgery principles. Its primary goal is to achieve rapid control of the infection through aggressive debridement of the affected tissue, in order to perform a complete reconstruction of the limb. This allows both its salvage and restoration of function. We present a patient with septic non-union secondary to distal tibia fracture with a bone defect of 7 cm and severe soft tissue injury. The treatment was divided into three stages. First, the infection was controlled by radical debridement, limb shortening, and temporary stabilization. Second, early reconstruction was initiated utilizing the first stage of the Masquelet's induced membrane technique (MIMT), and soft tissue coverage with free flap. Third, MIMT was finalized, and bone lengthening with PRECICE nail was performed. We consider this approach effective as it can offer early recovery with optimal functional and aesthetic results in bone defects associated with coverage defects.

Varying degrees of spontaneous osteogenesis of Masquelet's induced membrane: experimental and clinical observations

BACKGROUND

Masquelet's induced membrane (IM) has osteogenesis activity, but IM spontaneous osteogenesis (SO) has not been described previously.

OBJECTIVES

To report on varying degrees of IMSO and analyze its possible causes.

METHODS

Twelve eight-week-old male Sprague-Dawley rats with 10 mm right femoral bone defects who received the first stage of IM technique (IMT) were used to observe the SO. In addition, clinical data from patients with bone defects who received the first stage of IMT with an interval of > 2 months post-operatively and exhibited SO between January 2012 and June 2020 were retrospectively analyzed. The SO was divided into four grades according to the amount and characteristics of the new bone formation.

RESULTS

At twelve weeks, grade II SO was observed in all rats, and more new bone was formed in the IM near the bone end forming an uneven margin. Histology revealed bone and cartilage foci in the new bone. Four of the 98 patients treated with the first stage of IMT exhibited IMSO, including one female and three males with a median age of 40.5 years (range 29-52 years). The bone defects were caused by severe fractures and infection in two cases and by infection or tumor in one case each. Partial or segmental defects occurred in two cases. The time interval between inserting a cement spacer and diagnosis of SO ranged from six months to nine years. Two cases were grade I, and one case each of grades III and IV.

CONCLUSION

Varying degrees of SO confirm the existence of the IMSO phenomenon. Bioactive bone tissue or local inflammation and a long time interval are the primary reasons underlying enhancement of the osteogenic activity of IM and leading to SO, which tends to take place as endochondral osteogenesis.

Hydrogel Drug Delivery Systems for Bone Regeneration

With the in-depth understanding of bone regeneration mechanisms and the development of bone tissue engineering, a variety of scaffold carrier materials with desirable physicochemical properties and biological functions have recently emerged in the field of bone regeneration. Hydrogels are being increasingly used in the field of bone regeneration and tissue engineering because of their biocompatibility, unique swelling properties, and relative ease of fabrication. Hydrogel drug delivery systems comprise cells, cytokines, an extracellular matrix, and small molecule nucleotides, which have different properties depending on their chemical or physical cross-linking. Additionally, hydrogels can be designed for different types of drug delivery for specific applications. In this paper, we summarize recent research in the field of bone regeneration using hydrogels as delivery carriers, detail the application of hydrogels in bone defect diseases and their mechanisms, and discuss future research directions of hydrogel drug delivery systems in bone tissue engineering.

Induced membrane technique using bone cement with or without cefazolin in chicken segmental radius defect

The utilization of antibiotic-loaded cement spacer in the induced membrane development has been a debate topic in human medicine. To the best of the author's knowledge, these combinations have not yet been evaluated in birds. Therefore, this study assessed induced membrane formation using radiography and histology, in a segmental defect of a chicken radius, with or without the addition of cefazolin. Thirty 18-month-old healthy chickens were divided into two equal groups: G1-bone defect filled with bone cement; G2-bone defect filled with cefazolin powder-loaded bone cement. Radiographic examinations of the left forearm were taken immediately after surgery and at 7, 15, and 21 postoperative days. For the collection of the induced membranes, five chickens in each group were euthanized at 7, 15, and 21 days after surgery. Radiographically, the bone cement was identified as a radiopaque structure occupying the bone defect in both groups. Mild new bone formation in at least one of the fractured extremities of the bone defect was seen only 21 days after surgery in most chickens. Histologically, there was no difference in the mean thickness of the induced membrane between groups at all time points. Multifocal multinucleated cells differed between groups at 7 (G1 > G2) and 21 (G2 > G1) days after surgery. Mononuclear inflammatory infiltrate differed between groups only on day 21 (G1 > G2). Fibrous tissue proliferation did not differ between groups at all evaluation times. Blood vessel density differed only at 21 days postoperatively (G2 < G1). Multifocal areas of cartilage differed between groups at all time points (G1 > G2). In conclusion, cefazolin mixed with bone cement did not affect thickness of the induced membrane, but did result in a negative effect on some histological aspects, such as fewer vessels, less multifocal areas of cartilage, and persistence of inflammation.

Is the bioactivity of induced membranes time dependent?

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Masquelet technique in post-traumatic infected femoral and tibial segmental bone defects. Union and reoperation rates with high proportions (up to 64%) of allograft in the second stage

Introduction The aim of this study was to describe union, reoperation and failure rates after using the induced membrane (IM) technique with ≥50% allograft over autograft to treat infected femoral and tibial segmental bone defects (SBD). Materials and methods We retrospectively analyzed patients with femoral and tibial SBD treated in our center between 2012 and 2019 using ≥50% allograft over autograft during the second stage of the Masquelet technique. We analyzed the affected bone, defect size, osteosynthesis technique used, time elapsed between the first and second stage of the technique, graft proportions, union time, reoperations, and non-union rates. Results We included 21 patients (61.90% men) with a median age of 41 (range 18-68) years. The tibia was affected in 61.90% (n:13) and the femur in 38.09% (n:8) of the cases. SBD length was 4.5 (range 3.5-14) cm. The median interval between both stages of the technique was 10 (range 6-28) weeks. The proportion of allograft used was 50 % in 10 patients, 51 to 55% in 5 patients, 56 to 59% in 4 patients, and 60 to 64% in 2. The union rate was 95.23% over a median time of 7 (range 6-12) months. There were 3 (14.28%) reoperations: 2 for relapse of infection and 1 for mechanical instability. There was one failure (4.76%). One patient presented non-union and nail break. The median follow-up after the second stage of the technique was 26 (range 13-54) months. Conclusion The use of the induced membrane technique and a high proportion of allograft (up to 64%) achieved similar union and failure rates than those reported for similar series that relied on lower allograft proportions.

Management of surgical site infection post-open reduction and internal fixation for tibial plateau fractures

AIMS

In contrast to operations performed for other fractures, there is a high incidence rate of surgical site infection (SSI) post-open reduction and internal fixation (ORIF) done for tibial plateau fractures (TPFs). This study investigates the effect of induced membrane technique combined with internal fixation for managing SSI in TPF patients who underwent ORIF.

METHODS

From April 2013 to May 2017, 46 consecutive patients with SSI post-ORIF for TPFs were managed in our centre with an induced membrane technique. Of these, 35 patients were included for this study, with data analyzed in a retrospective manner.

RESULTS

All participants were monitored for a mean of 36 months (24 to 62). None were subjected to amputations. A total of 21 patients underwent two-stage surgeries (Group A), with 14 patients who did not receive second-stage surgery (Group B). Group A did not experience infection recurrence, and no implant or cement spacer loosening was noted in Group B for at least 24 months of follow-up. No significant difference was noted in the Lower Extremity Functional Scale (LEFS) and the Hospital for Special Surgery Knee Score (HSS) between the two groups. The clinical healing time was significantly shorter in Group B (p＜0.001). Those with longer duration of infection had poorer functional status (p＜0.001).

CONCLUSION

Management of SSI post-ORIF for TPF with induced membrane technique combined with internal fixation represents a feasible mode of treatment with satisfactory outcomes in terms of infection control and functional recovery. Cite this article: Bone Joint Res 2021;10(7):380-387.

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-Induced Membrane Characteristics in Chicken Radii Bone Defects

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

Masquelet’s induced membrane technique for the reconstruction of post-traumatic, open-grade distal femur fracture with bone defect

Introduction:

Reconstruction of complex, open-grade distal femur fracture with bone defect presents an orthopaedic surgeon with a distinctive challenge as they are often associated with contaminated, compromised soft tissue and poor host condition. Conventional techniques like vascularized fibula transfer, autologous bone grafting or distraction osteogenesis focus mainly over bone union without taking infection control into consideration. The aim of this study is to evaluate the outcome of induced membrane technique in the reconstruction of open distal femur fracture with bone defect.

Methods:

10 such patients were retrospectively evaluated. Union was considered when a minimum of two cortices were seen on a radiograph. Knee Society Score was used to evaluate the functional outcome.

Results:

The average length of the defect was 5.7cm (3–10 cm) with mean interval period between the two stages being 42.7 days (34–51 days). Internal fixation was carried out in all cases. In 7 patients we used a mixture of cancellous autograft and cancellous allograft mixed in a ratio of 3:1. In the remaining 3 patients we used only cancellous autograft. Radiological union was achieved in all patients with mean union time of 8.5 months (7–11 months). Mean knee score was 79 (69–86) and mean function score was 71.5 (60–80).

Conclusion:

The induced membrane technique is an economical, technically less demanding technique for reconstruction of distal femur fracture with bone defects. The results are reproducible with a high success rate and without the need of any special instrumentation. It bestows infection control and prevents graft resorption. Long reconstructive period and donor site morbidity are matters of concern.

Salvage Reconstruction With the Masquelet Technique Following Wide Resection for Chondrosarcoma of the Proximal Femoral Metaphysis: A Case Report

BACKGROUND

Bone reconstruction following a wide resection for a malignant musculoskeletal tumor remains challenging, especially for an intercalary defect following the resection of a metaphyseal lesion.

CASE REPORT

Here, we describe a surgical procedure using the Masquelet technique for the biological reconstruction of a huge subtrochanteric bone defect following failed pasteurized autologous bone grafting for a conventional chondrosarcoma of the proximal femoral metaphysis with a subtrochanteric pathological fracture. The patient, a 43-year-old Japanese male, was able to walk without a cane or a brace at 15 months after the final operation (International Society of Limb Salvage score, 86.7%).

CONCLUSION

This procedure should be considered as one of the reconstruction options following the wide resection of malignant bone tumors located in the metaphysis.

Management of Osteomyelitis in Sickle Cell Disease: Review Article

Sickle cell disease (SCD) is an autosomal recessive disorder that is characterized by abnormal “sickle-shaped” erythrocytes. Because of their shape, these erythrocytes are more likely to become trapped in small slow-flowing vessels, leading to vaso-occlusion. Because this commonly happens in the bones, patients with SCD are at an increased risk for orthopaedic manifestations such as osteomyelitis, septic joint, or osteonecrosis. Osteomyelitis is a serious and potentially disabling condition but can be difficult to differentiate from benign conditions of SCD, such as vaso-occlusive crisis. Diagnosis of osteomyelitis requires careful evaluation of the clinical presentation, laboratory testing, and imaging. Treatment of osteomyelitis in patients with SCD may be medical or surgical, but considerations in antibiotic selection and management preoperatively and postoperatively must be taken to ensure optimal outcomes.

Application of the Masquelet technique in austere environments: experience from a French forward surgical unit deployed in Chad

PURPOSE

We sought to evaluate the results of the Masquelet-induced membrane technique (IMT) for long bone defect reconstruction within the limited-resource setting of a French forward surgical unit deployed in Chad.

METHODS

A prospective and observational study was conducted in all patients with a traumatic segmental bone defect in any anatomical location treated by IMT from November 2015 to December 2019. Although IMT was applied by various orthopedic surgeons with variable expertise, all followed the same surgical protocol. Endpoint assessment was performed 12 months after IMT application.

RESULTS

Sixteen patients with a mean age of 32.7 years were included in the study. Bone defects were located on the tibia (n = 8), the femur (n = 6) or the radius (n = 2). Thirteen bone defects were infected. After debridement, the mean bone defect length was 4.3 cm. External fixation of the tibia and femur was predominant in both stages. Bone union was achieved in only 8 of the 16 cases at a mean time of 7.6 months. All failures were related to persistent infection or insufficient fixation stability in the second stage.

CONCLUSIONS

This series is the first to report IMT use in a forward surgical unit. Despite frequent complications, local patients can benefit from this procedure, which is the only available method for bone reconstruction in areas with limited medical resources. A rigorous technical completion at both stages is crucial to limit septic or mechanical failures.

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.

Scaffolds and coatings for bone regeneration

Bone tissue has an astonishing self-healing capacity yet only for non-critical size defects (<6 mm) and clinical intervention is needed for critical-size defects and beyond that along with non-union bone fractures and bone defects larger than critical size represent a major healthcare problem. Autografts are, still, being used as preferred to treat large bone defects. Mostly, due to the presence of living differentiated and progenitor cells, its osteogenic, osteoinductive and osteoconductive properties that allow osteogenesis, vascularization, and provide structural support. Bone tissue engineering strategies have been proposed to overcome the limited supply of grafts. Complete and successful bone regeneration can be influenced by several factors namely: the age of the patient, health, gender and is expected that the ideal scaffold for bone regeneration combines factors such as bioactivity and osteoinductivity. The commercially available products have as their main function the replacement of bone. Moreover, scaffolds still present limitations including poor osteointegration and limited vascularization. The introduction of pores in scaffolds are being used to promote the osteointegration as it allows cell and vessel infiltration. Moreover, combinations with growth factors or coatings have been explored as they can improve the osteoconductive and osteoinductive properties of the scaffold. This review focuses on the bone defects treatments and on the research of scaffolds for bone regeneration. Moreover, it summarizes the latest progress in the development of coatings used in bone tissue engineering. Despite the interesting advances which include the development of hybrid scaffolds, there are still important challenges that need to be addressed in order to fasten translation of scaffolds into the clinical scenario. Finally, we must reflect on the main challenges for bone tissue regeneration. There is a need to achieve a proper mechanical properties to bear the load of movements; have a scaffolds with a structure that fit the bone anatomy.

Management of Infected Bone Defects of the Lower Extremities by Three-Stage Induced Membrane Technique

BACKGROUND Infected bone defects are therapeutic challenges. Although the induced membrane technique has been used for this problem, there is a 3% to 20.7% failure to eradicate infection, and there have been few reports about its use in tuberculous infection. We present our three-stage induced membrane technique (TSIMT) for treating infected bone defects of the lower extremity. MATERIAL AND METHODS Forty-one adult patients with infected bone defects of the lower extremities treated by TSIMT were included in a retrospective case-series study between January 2013 and June 2018. The clinical, imaging and laboratory assessment outcomes were analyzed. RESULTS In the first stage, 3 patients had ankle tuberculous bone defects and 17 patients underwent 2-4 debridements. In the second stage, the average bone defect was 6.0 cm; 1 patient needed an anterolateral thigh flap to cover the wound. In the third stage, 10 patients underwent autograft mixed allograft, and 18 cases used internal fixation. The mean follow-up period was 23.3 months. All patients achieved bone union and clinical eradication of infection. Changes in Lower Extremity Functional Scale (LEFS) scores after 1 year of TSIMT and bone union time are associated with advanced age, longer duration of infected bone defects, active smoking, and external fixation (p<0.05), but are not dependent on bone defect size, debridement times, type of bone graft, or spacer-placing time (p>0.05). CONCLUSIONS TSIMT is effective in treating infected bone defects of the lower extremities. Advanced age, longer duration of infected bone defects, active smoking, and external fixation adversely affect bone union and recovery of infected extremities in a limited time span.

Reconstruction of Large Skeletal Defects: Current Clinical Therapeutic Strategies and Future Directions Using 3D Printing

The healing of bone fractures is a well-orchestrated physiological process involving multiple cell types and signaling molecules interacting at the fracture site to replace and repair bone tissue without scar formation. However, when the lesion is too large, normal healing is compromised. These so-called non-union bone fractures, mostly arising due to trauma, tumor resection or disease, represent a major therapeutic challenge for orthopedic and reconstructive surgeons. In this review, we firstly present the current commonly employed surgical strategies comprising auto-, allo-, and xenograft transplantations, as well as synthetic biomaterials. Further to this, we discuss the multiple factors influencing the effectiveness of the reconstructive therapy. One essential parameter is adequate vascularization that ensures the vitality of the bone grafts thereby supporting the regeneration process, however deficient vascularization presents a frequently encountered problem in current management strategies. To address this challenge, vascularized bone grafts, including free or pedicled fibula flaps, or in situ approaches using the Masquelet induced membrane, or the patient’s body as a bioreactor, comprise feasible alternatives. Finally, we highlight future directions and novel strategies such as 3D printing and bioprinting which could overcome some of the current challenges in the field of bone defect reconstruction, with the benefit of fabricating personalized and vascularized scaffolds.

Does the induced membrane have antibacterial properties? An experimental rat model of a chronic infected nonunion

INTRODUCTION

The Masquelet procedure proved its efficiency in treating infected nonunion filling bony gaps up to 25 cm. Yet the use of local antibiotics is still questionable in the daily practice with lack of evidence regarding its usefulness in controlling infection. An experimental rat model is put in place to study the antibacterial properties of the induced membrane produced during the first stage of Masquelet.

METHOD

Twenty-three-month-old wistar male rats are inoculated with a 0.5 mL solution of 10^8 CFU/mL MRSA over a critical fracture done on the right femur. Six weeks later, remaining 11 rats exhibiting signs of a chronic infection with a sinus tract and oozing pus along with radiological nonunion are used for a first stage Masquelet procedure. They are randomly divided into two groups with six rats having no local antibiotic in the cement mixture and five rats having 3 g of vancomycin mixed with gentamycin loaded cement. Six weeks later (twelve weeks from baseline), all eleven rats are euthanized and blood samples for C-reactive protein are withdrawn. The induced membrane is identified and resected along with bone fragments and sent for cultures and pathology.

RESULTS

MRSA is isolated in the cultures of all six rats in the first group where no local antibiotic was added. Altered polymorphonuclears with abscess and pus are noted on four of six pathology samples. However in the second group where local antibiotics were added, three out of five rats exhibited eradication of MRSA (p = 0.034) and all samples did not exhibit clear infection signs on pathology. A pyo-epithelioid over a foreign body reaction is seen predominantly in this group demonstrating a regenerative process.

DISCUSSION

The induced membrane does not have antimicrobial properties capable of overcoming an infected nonunion on its own. When local antibiotics were added during the first stage of the Masquelet procedure, new bone formation occurred indicating the need to control an infection in order for bone union to occur.

CONCLUSION

Local antibiotics use in adjunction to extensive debridement is advisable during the first stage of a Masquelet procedure for an infected nonunion.

A Bioactive Coating Enhances Bone Allografts in Rat Models of Bone Formation and Critical Defect Repair

Bone allografts are inferior to autografts for the repair of critical-sized defects. Prior studies have suggested that bone morphogenetic protein-2 (BMP-2) can be combined with allografts to produce superior healing. We created a bioactive coating on bone allografts using polycondensed deoxyribose isobutyrate ester (PDIB) polymer to deliver BMP-2 ± the bisphosphonate zoledronic acid (ZA) and tested its ability to enhance the functional utility of allografts in preclinical Wistar rat models. One ex vivo and two in vivo proof-of-concept studies were performed. First, PDIB was shown to be able to coat bone grafts (BGs). Second, PDIB was used to coat structural allogenic corticocancellous BG with BMP-2 ± ZA ± hydroxyapatite (HA) microparticles and compared with PDIB-coated grafts in a rat muscle pouch model. Next, a rat critical defect model was performed with treatment groups including (i) empty defect, (ii) BG, (iii) collagen sponge + BMP-2, (iv) BG + PDIB/BMP-2, and (v) BG + PDIB/BMP-2/ZA. Key outcome measures included detection of fluorescent bone labels, microcomputed tomography (CT) quantification of bone, and radiographic healing. In the muscle pouch study, BMP-2 did not increase net bone volume measured by microCT, however, fluorescent labeling showed large amounts of new bone. Addition of ZA increased BV by sevenfold (p < 0.01). In the critical defect model, allografts were insufficient to promote reliable union, however, union was achieved in collagen/BMP-2 and all BG/BMP-2 groups. Statement of clinical significance: These data support the concept that PDIB is a viable delivery method for BMP-2 and ZA delivery to enhance the bone forming potential of allografts. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2278-2286, 2019.

Outcomes of Vacuum Sealing Drainage Treatment Combined with Skin Flap Transplantation and Antibiotic Bone Cement on Chronic Tibia Osteomyelitis: A Case Series Study

BACKGROUND Chronic osteomyelitis is one of the currently refractory diseases. The aim of this study is to discuss the method and curative effects of vacuum sealing drainage (VSD) treatment combined with skin flap transplantation and antibiotic bone cement for chronic tibia osteomyelitis. MATERIAL AND METHODS For this study, 18 cases of open fracture secondary chronic tibia osteomyelitis were selected. After the granulation tissue of the wound surface became fresh and infection was controlled, the wound surface was repaired with a medial head of gastrocnemius transfer flap or a myofascial and cutaneous island pedicle flap with a collateral vessel nourished by the retrograde sural nerve. VSD combined with focus debridement and antibiotic bone cement filling was conducted. After inflammation was completely regulated, elective bone cement extraction, bone grafting, and internal fixation were performed. Within 2 to 3 years of follow-up post-surgery, the satisfaction and recurrence rates were evaluated. The patients' pre-operative and post-operative recovery of limb functions were compared according to the Enneking scoring system. RESULTS The patients did not suffer from osteomyelitis recurrence, with the exception of 1 case that manifested osteomyelitis recurrence and recovered through surgical treatment within the period of follow-up. The satisfaction and recurrence rates of these study cases post-surgery were 94.4% and 5.6%, respectively. The average functional recovery post-surgery was 81.5% of normal function. CONCLUSIONS Vacuum sealing drainage combined with skin flap transplantation and antibiotic bone cement is an effective treatment for chronic tibia osteomyelitis.

Masquelet induced membrane technique for treatment of rat chronic osteomyelitis

The application value of Masquelet induced membrane technique for the treatment of rat chronic osteomyelitis was explored. A total of 180 male Sprague-Dawley (SD) rats were randomly divided into sham operation group (control group), chronic osteomyelitis model group (model group) and Masquelet induced membrane therapy + chronic osteomyelitis model group (observation group); 60 rats in each group. A rat model of traumatic osteomyelitis was established using a modified blunt trauma method in model and observation group. All rats in observation group were treated with membrane induction technology while in the control group they were not. Postoperative complications, bone healing time and functional status of the affected limbs were recorded. After surgery, no obvious perioperative complications occurred in most of the rats, except that 5 rats experienced partial necrosis at the edge of the flap, and 3 experienced superficial infection around the incision site in the ilium. Primary bone healing was achieved in 50 rats with an average healing time of 15 weeks. Among them, 38 rats restored weight-bearing function after 20 weeks. Seven rats experienced infection after surgery, but complete bone healing was achieved after treatment with induced membrane technique again. Following treatment with induced membrane technique, the rat body weight, body temperature and the number of bacteria in the wound decreased over time. In conclusion, Masquelet induced membrane technique is effective for the treatment of large bone defects in rats after traumatic osteomyelitis. This technique significantly shortens the treatment cycle. The surgical procedure is simple, and the incidence of postoperative complications is low.

Inhibition of Dll4/Notch1 pathway promotes angiogenesis of Masquelet's induced membrane in rats

The Masquelet’s induced membrane technique for repairing bone defects has been demonstrated to be a promising treatment strategy. Previous studies have shown that the vessel density of induced membrane is decreased in the late stage of membrane formation, which consequently disrupts the bone healing process. However, relatively little is known about certain mechanisms of vessel degeneration in the induced membrane tissue and whether promotion of angiogenesis in induced membranes can improve bone regeneration. Here, we showed that the Delta-like ligand 4/ Notch homolog 1 (Dll4/Notch1) pathway was relatively activated in the late stage of induced membrane, especially at the subcutaneous site. Then, DAPT, a classical γ-secretase inhibitor, was applied to specifically inhibit Notch1 activation, followed by up-regulation of vascular endothelial growth factor receptor 2 (VEGFR2) and CD31 expression. DAPT-modified induced membranes were further confirmed to contribute to bone regeneration after autogenous bone grafting. Finally, in vitro experiments revealed that knocking down Notch1 contributed to the functional improvement of endothelial progenitor cells (EPCs) and that DAPT-treated induced membrane tissue was more favorable for angiogenesis of EPCs compared with the vehicle group. In conclusion, the present findings demonstrate that Dll4/Notch1 signaling is negatively associated with the vessel density of induced membrane. Pharmacological inhibition of Notch1 attenuated the vessel degeneration of induced membrane both in vitro and in vivo, which consequently improved bone formation at the bone defect site and graft resorption at the subcutaneous site.

Repairs to serious bone injuries may be improved by blocking a signaling pathway that causes newly forming membranes to fail. Masquelet’s technique involves placing acrylic spacers in areas of bone damage, inducing the formation of vascularised membranes which encourage the body to accept bone grafts. However, sometimes Masquelet’s membranes do not form correctly, leading to weaknesses in bone repairs and potential graft rejection. In experiments on rats, Qian Tang from Wenzhou Medical University, China, and coworkers found that a particular signaling pathway, D114/Notch1, was upregulated around 6 weeks post-operation, reducing blood vessel density and limiting new vessel growth, weakening the membranes. The team inhibited this pathway using an existing therapy that prevents blood clots. This treatment improved bone repairs by promoting the formation and function of blood vessels in membranes.