The 'diamond concept' for long bone non-union management

Clinical management and innovation in fracture non-union

INTRODUCTION

With the introduction and continuous improvement in operative fracture fixation, even the most severe bone fractures can be treated with a high rate of successful healing. However, healing complications can occur and when healing fails over prolonged time, the outcome is termed a fracture non-union. Non-union is generally believed to develop due to inadequate fixation, underlying host-related factors, or infection. Despite the advancements in fracture fixation and infection management, there is still a clear need for earlier diagnosis, improved prediction of healing outcomes and innovation in the treatment of non-union.

AREAS COVERED

This review provides a detailed description of non-union from a clinical perspective, including the state of the art in diagnosis, treatment, and currently available biomaterials and orthobiologics.Subsequently, recent translational development from the biological, mechanical, and infection research fields are presented, including the latest in smart implants, osteoinductive materials, and in silico modeling.

EXPERT OPINION

The first challenge for future innovations is to refine and to identify new clinical factors for the proper definition, diagnosis, and treatment of non-union. However, integration of in vitro, in vivo, and in silico research will enable a comprehensive understanding of non-union causes and correlations, leading to the development of more effective treatments.

[Reconstruction options for infection-related defects : Plastic surgery armamentarium]

BACKGROUND

The occurrence of infections has always been feared in all surgical disciplines. Plastic reconstructive surgery faces the challenge of treating infection-related defects on a patient-specific basis, which requires a multidisciplinary treatment concept. Satisfactory treatment success can only be achieved through radical debridement for infection cleansing, optimization of the perfusion situation paired with targeted anti-infective treatment and, if necessary, with soft tissue reconstruction by plastic surgery.

OBJECTIVE

This article presents the current possibilities of plastic and reconstructive surgery with respect to the reconstruction of infection-related defects.

MATERIAL AND METHODS

Proven and reliable strategies are presented and supplemented by promising experimental approaches.

RESULTS

Due to the often multilayered defect situation caused by infections, from the epidermis to cancellous bone, the entire armamentarium of plastic and reconstructive surgery is used for reconstruction.

CONCLUSION

The early involvement of plastic surgery in the treatment of infections and the interdisciplinary and multimodal treatment approach have proven their worth in the treatment of complex infection situations.

[Is the 95°blade plate still important in the treatment of proximal femoral pseudarthrosis?]

Due to demographic changes, fractures and subsequently delayed fracture healing as well as pseudarthrosis of the proximal femur are on the increase. In the acute fracture situation, a load-stable treatment with an intramedullary implant (cephalomedullary nail) is generally sought. To date, there is no uniform consensus on the optimal treatment for complicated cases. The aim of this study was to evaluate the clinical and radiological outcome after revision of pseudarthrosis using a 95° blade plate in aseptic proximal femoral pseudarthrosis and to identify the specifications of blade plate treatment.The retrospective study design was used to evaluate data, some of which were prospectively collected. The study period covered January 2010 to December 2020 and 22 patients (10 women, 12 men) with an average age of 59 years were included in this single-center study. All patients showed pseudarthrosis after a femoral fracture type AO 31 A1-A3 or proximal femoral fracture type AO 32 A-C. Clinical and radiological follow-up were performed after 3, 6 and 12 months. Functional outcomes were assessed using the modified Harris hip score (mHHS), the numerical rating scale (NRS) and the short form health survey (SF-12).The postoperative radiological results after reosteosynthesis using a blade plate showed good results and 86.4% of the patient population were healed during the observation period. Pseudarthrosis persisted in four patients and was surgically revised.The functional results showed good results on average, albeit with a high dispersion of 17-91 points in the mHHS. The SF-12 averaged 42.6 (±10.4) points and the psychological score 49.4 (±9.6) points. The postoperative pain level was low both at rest and under stress.It was shown that reosteosynthesis with a blade plate is a surgically demanding but effective treatment option with a low potential for infection and safe bone consolidation, especially for the correction of high-grade axial deviation or varus malalignment.

Efficacy and safety of recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with autologous bone for the treatment of long bone nonunion: A report of a prospective case series

INTRODUCTION

Recombinant human Bone morphogenetic proteins have been used for the treatment of nonunions with promising results. We have been investigating both experimentally and clinically the efficacy of the rhBMP-2 with the macro / micro-porous hydroxyapatite carrier granules on the potency on the reconstruction of long bone defect. The purpose of this study was to prospectively evaluate the efficacy and safety of this specific rhBMP-2 with HA carrier granules mixed with autologous cancellous bone in patients with nonunion and bone defect resulted from the fracture related infection.

MATERIALS AND METHODS

This was a retrospective review of a prospective cohort at a university hospital. Patients diagnosed with nonunion under the definition of the United States Food and Drug Administration with bone defect after long bone fractures were enrolled from January 2020 to February 2021. We included patients with atrophic and oligotrophic nonunion, and hypertrophic nonunion with malalignment that needed to be corrected. The other patient group was consisted of segmental bone defect resulted from FRI. The maximum amount of rhBMP-2 allowed in this clinical study was 6 mg and was added to autologous bone at a 1:1 ratio. Autologous bone was added to the mixture if the volume of mixed graft was insufficient to fill the bone defect. Patients were followed 3, 6, and 12 months post-operatively. Each visit, a radiograph was taken for assessment. Visual analog scale (VAS), questionnaire for quality of life (SF-12 physical component summary [PCS], mental component summary [MCS]), and weight-bearing status were collected for functional outcome assessment. Drug safety was assessed by examining BMP-2 antibodies.

RESULTS

Of the 24 enrolled patients (mean age: 57 years), 15 (62.5 %), 2 (8.33 %), and 7 (29.17 %) presented atrophic nonunion, hypertrophic nonunion with deformity, and bone defect after fracture related infection, respectively. Thirteen patients had nonunion in the femur, 9 in the tibia, and 1 in the humerus and radius. The average amount of harvested autologous bone was 9.25 g and 4.96 mg of rhBMP-2. All 24 patients achieved union after 1-year follow up. The union rate was 95.83 % and 100 % at 6 and 12 months postoperatively, respectively. Preoperative SF-12 PCS (mean: 34.71) improved at 6 and 12 months postoperatively, respectively. Preoperative SF-12 MCS (mean: 42.89) improved 12 months postoperatively (49.13, p = 0.0338). Change of VAS was statistically significant 3 months postoperatively (p = 0.0012). No adverse effects or development of BMP-2 antibodies were observed.

CONCLUSION

BMP-2 combined with autogenous bone resulted in excellent radiographical and functional outcomes in a relatively small prospective series of patients with nonunion and bone defect, without adverse effects. Further investigations are necessary to support our finding and optimize treatment strategies in nonunion patients.

The effect of green mussel ( Perna viridis) shells' hydroxyapatite application on alkaline phosphatase levels in rabbit femur bone defect

Background

Non-union fractures can be prevented with bone grafts, such as hydroxyapatite made from green mussel shells. Green mussel shells contain a high percentage of HA, making them a promising alternative for bone healing. This research aims to reveal the effectiveness of green mussel shell HA as a bone substitute material and to provide knowledge for further research.

Methods

This research was conducted for four months using a true experimental research method with a post-test-only control group design. This study used 36 New Zealand rabbits ( Oryctolagus cuniculus) which were divided into 9 groups: positive control, negative control, and intervention at weeks 2, 4 and 6 after the intervention. All groups were subjected to three general procedures: pre-surgery, surgery, and post-surgery. This study utilized histological evaluation and biochemical assessment, specifically measuring serum alkaline phosphatase (ALP) levels, to investigate the effects of hydroxyapatite (HA) from green mussel shells on bone healing in rabbits.

Results

The findings demonstrated that green mussel shell HA hashad efficacy in accelerating bone healing, better than HA bovine HA i.e. green mussel shell hydroxyapatite showed superior efficacy compared to bovine hydroxyapatite in accelerating and maximizing fracture healing, as compared to the 6-week negative control group and demonstrated a significant difference ( p < 0.05).

Conclusions

Green mussel hydroxyapatite is proven to be able to fasten and maximize the bone healing process as fast as bovine HA, and even has higher efficacy than bovine HA.

Angiogenesis is uncoupled from osteogenesis during calvarial bone regeneration

Bone regeneration requires a well-orchestrated cellular and molecular response including robust vascularization and recruitment of mesenchymal and osteogenic cells. In femoral fractures, angiogenesis and osteogenesis are closely coupled during the complex healing process. Here, we show with advanced longitudinal intravital multiphoton microscopy that early vascular sprouting is not directly coupled to osteoprogenitor invasion during calvarial bone regeneration. Early osteoprogenitors emerging from the periosteum give rise to bone-forming osteoblasts at the injured calvarial bone edge. Microvessels growing inside the lesions are not associated with osteoprogenitors. Subsequently, osteogenic cells collectively invade the vascularized and perfused lesion as a multicellular layer, thereby advancing regenerative ossification. Vascular sprouting and remodeling result in dynamic blood flow alterations to accommodate the growing bone. Single cell profiling of injured calvarial bones demonstrates mesenchymal stromal cell heterogeneity comparable to femoral fractures with increase in cell types promoting bone regeneration. Expression of angiogenesis and hypoxia-related genes are slightly elevated reflecting ossification of a vascularized lesion site. Endothelial Notch and VEGF signaling alter vascular growth in calvarial bone repair without affecting the ossification progress. Our findings may have clinical implications for bone regeneration and bioengineering approaches.

Cellular therapies for bone repair: current insights

Mesenchymal stem cells are core to bone homeostasis and repair. They both provide the progenitor cells from which bone cells are formed and regulate the local cytokine environment to create a pro-osteogenic environment. Dysregulation of these cells is often seen in orthopaedic pathology and can be manipulated by the physician treating the patient. This narrative review aims to describe the common applications of cell therapies to bone healing whilst also suggesting the future direction of these techniques.

Long bone uninfected non-union: grafting techniques

Long bone non-unions represent a serious clinical and socioeconomical problem due to the prolonged episodes, frequent sequelae, and variable treatment effectiveness. Bone grafts, classically involving the autologous iliac crest graft as the 'gold standard' bone graft, enhance bone regeneration and fracture healing incorporating osteoconductive and/or osteoinductive/osteogenic capacity to the non-union under treatment. Structural alternatives to autologous bone grafts include allografts and bone substitutes, expanding the available stock but loosing biological properties associated with cells in the graft. Biological alternatives to autologous bone grafts include bone marrow concentration from iliac crest aspiration, bone marrow aspiration from reaming of the diaphyseal medullary canal in the long bones, and isolated, expanded mesenchymal stem cells under investigation. When the combination with natural and synthetic bone substitutes allows for larger volumes of structural grafts, the enhancement of the biological regenerative properties through the incorporation of cells and their secretoma permits to foresee new bone grafting solutions and techniques.

Polytherapy versus monotherapy in the treatment of tibial non-unions: a retrospective study

BACKGROUND

Treating tibial non-unions efficiently presents a challenge for orthopaedic trauma surgeons. The established gold standard involves implanting autologous bone graft with adequate fixation, but the addition of biologicals according to the so-called diamond concept has become increasingly popular in the treatment of non-unions. Previous studies have indicated that polytherapy, which involves implanting mesenchymal stem cells, bioactive factors and osteoconductive scaffolds, can improve bone healing. This study aims to evaluate the efficacy of polytherapy compared with monotherapy in treating tibial non-unions of varying severity.

MATERIALS AND METHODS

Data from consecutive tibial non-unions treated between November 2014 and July 2023 were retrospectively analysed. The Non Union Scoring System (NUSS) score before non-union surgery, and the Radiographic Union Score for Tibial fractures (RUST), scored at 1, 3, 6, 9, 12 and 18 months post-surgery, were recorded. Initially, a comparison was made between the polytherapy and monotherapy groups. Subsequently, patients receiving additional surgical non-union treatment were documented, and the frequency of these treatments was tallied for a subsequent per-treatment analysis.

RESULTS

A total of 34 patients were included and divided into a polytherapy group (n = 15) and a monotherapy group (n = 19). The polytherapy group demonstrated a higher NUSS score (44 (39, 52) versus 32 (29, 43), P = 0.019, z = -2.347) and a tendency towards a higher success rate (93% versus 68%, P = 0.104) compared with the monotherapy group. For the per-treatment analysis, 44 treatments were divided into the polytherapy per-treatment group (n = 20) and the monotherapy per-treatment group (n = 24). The polytherapy per-treatment group exhibited a higher NUSS score (48 (43, 60) versus 38 (30, 50), P = 0.030, z = -2.173) and a higher success rate (95% versus 58%, P = 0.006) than the monotherapy per-treatment group. Within the monotherapy per-treatment group, the NUSS score displayed excellent predictive performance (AUC = 0.9143). Setting the threshold value at 48, the sensitivity and specificity were 100.0% and 70.0%, respectively.

CONCLUSIONS

Polytherapy is more effective than monotherapy for severe tibial non-unions, offering a higher success ratio. The NUSS score supports decision-making in treating tibial non-unions.

LEVEL OF EVIDENCE

Level III.

Association between Bone Turnover Markers and Fracture Healing in Long Bone Non-Union: A Systematic Review

Background: Fracture healing is a very complex and well-orchestrated regenerative process involving many cell types and molecular pathways. Despite the high efficiency of this process, unsatisfying healing outcomes, such as non-union, occur for approximately 5-10% of long bone fractures. Although there is an obvious need to identify markers to monitor the healing process and to predict a potential failure in callus formation to heal the fracture, circulating bone turnover markers' (BTMs) utility as biomarkers in association with radiographic and clinical examination still lacks evidence so far. Methods: A systematic review on the association between BTMs changes and fracture healing in long bone non-union was performed following PRISMA guidelines. The research papers were identified via the PubMed, Cochrane, Cinahl, Web of Science, Scopus, and Embase databases. Studies in which the failure of fracture healing was associated with osteoporosis or genetic disorders were not included. Results: A total of 172 studies were collected and, given the inclusion criteria, 14 manuscripts were included in this review. Changes in circulating BTMs levels were detected during the healing process and across groups (healed vs. non-union patients and healthy vs. patients with non-union). However, we found high heterogeneity in patients' characteristics (fracture site, gender, and age) and in sample scheduling, which made it impossible to perform a meta-analysis. Conclusions: Clinical findings and radiographic features remain the two important components of non-union diagnosis so far. We suggest improving blood sample standardization and clinical data collection in future research to lay the foundations for the effective use of BTMs as tools for diagnosing non-union.

Analysis of risk factors and development of a nomogram-based prediction model for defective bony non-union

Objective

To explore risk factors for defective non-union of bone and develop a nomogram-based prediction model for such an outcome.

Methods

This retrospective study analysed the case data of patients with defective bony non-unions who were treated at the authors' hospital between January 2010 and December 2020. Patients were divided into the union and non-union groups according to their Radiographic Union Score for Tibia scores 1 year after surgery. Univariate analysis was performed to assess factors related to demographic characteristics, laboratory investigations, surgery, and trauma in both groups. Subsequently, statistically significant factors were included in the multivariate logistic regression analysis to identify independent risk factors. A nomogram-based prediction model was established using statistically significant variables in the multivariate analysis. The accuracy and stability of the model were evaluated using receiver operating characteristic (ROC) and calibration curves. The clinical applicability of the nomogram model was evaluated using decision curve analysis.

Results

In total, 204 patients (171 male, 33 female; mean [±SD] age, 39.75 ± 13.00 years) were included. The mean body mass index was 22.95 ± 3.64 kg/m2. Among the included patients, 29 were smokers, 18 were alcohol drinkers, and 21 had a previous comorbid systemic disease (PCSD). Univariate analysis revealed that age, occupation, PCSD, smoking, drinking, interleukin-6, C-reactive protein (CRP), procalcitonin, alkaline phosphatase, glucose, and uric acid levels; blood calcium ion concentration; and bone defect size (BDS) were correlated with defective bone union (all P < 0.05). Multivariate logistic regression analysis revealed that PCSD, smoking, interleukin-6, CRP, and glucose levels; and BDS were associated with defective bone union (all P < 0.05), and the variables in the multivariate analysis were included in the nomogram-based prediction model. The value of the area under the ROC curve for the predictive model for bone defects was 0.95.

Conclusion

PCSD, smoking, interleukin-6, CRP, and glucose levels; and BDS were independent risk factors for defective bony non-union, and the incidence of such non-union was predicted using the nomogram. These findings are important for clinical interventions and decision-making.

Magnetic biocomposite scaffold based on decellularized tendon ECM and MNP-deposited halloysite nanotubes: physicochemical, thermal, rheological, mechanical andin vitrobiological evaluations

The development of new three-dimensional biomaterials with advanced versatile properties is critical to the success of tissue engineering (TE) applications. Here, (a) bioactive decellularized tendon extracellular matrix (dECM) with a sol-gel transition feature at physiological temperature, (b) halloysite nanotubes (HNT) with known mechanical properties and bioactivity, and (c) magnetic nanoparticles (MNP) with superparamagnetic and osteogenic properties were combined to develop a new scaffold that could be used in prospective bone TE applications. Deposition of MNPs on HNTs resulted in magnetic nanostructures without agglomeration of MNPs. A completely cell-free, collagen- and glycosaminoglycan- rich dECM was obtained and characterized. dECM-based scaffolds incorporated with 1%, 2% and 4% MNP-HNT were analysed for their physical, chemical, andin vitrobiological properties. Fourier-transform infrared spectroscopy, x-ray powder diffractometry and vibrating sample magnetometry analyses confirmed the presence of dECM, HNT and MNP in all scaffold types. The capacity to form apatite layer upon incubation in simulated body fluid revealed that dECM-MNP-HNT is a bioactive material. Combining dECM with MNP-HNT improved the thermal stability and compressive strength of the macroporous scaffolds upto 2% MNP-HNT.In vitrocytotoxicity and hemolysis experiments showed that the scaffolds were essentially biocompatible. Human bone marrow mesenchymal stem cells adhered and proliferated well on the macroporous constructs containing 1% and 2% MNP-HNT; and remained metabolically active for at least 21 din vitro. Collectively, the findings support the idea that magnetic nanocomposite dECM scaffolds containing MNP-HNT could be a potential template for TE applications.

Preventing Atrophic Long-Bone Nonunion: Retrospective Analysis at a Level I Trauma Center

Background: Among the risk factors for nonunion are unchangeable patient factors such as the type of injury and comorbidities, and factors that can be influenced by the surgeon such as fracture treatment and the postoperative course. While there are numerous studies analyzing unchangeable factors, there is poor evidence for factors that can be affected by the physician. This raises the need to fill the existing knowledge gaps and lay the foundations for future prevention and in-depth treatment strategies. Therefore, the goal of this study was to illuminate knowledge about nonunion in general and uncover the possible reasons for their development; Methods: This was a retrospective analysis of 327 patients from 2015 to 2020 from a level I trauma center in Germany. Information about patient characteristics, comorbidities, alcohol and nicotine abuse, fracture classification, type of osteosynthesis, etc., was collected. Matched pair analysis was performed, and statistical testing performed specifically for atrophic long-bone nonunion; Results: The type of osteosynthesis significantly affected the development of nonunion, with plate osteosynthesis being a predictor for nonunion. The use of wire cerclage did not affect the development of nonunion, nor did the use of NSAIDs, smoking, alcohol, osteoporosis and BMI; Conclusion: Knowledge about predictors for nonunion and strategies to avoid them can benefit the medical care of patients, possibly preventing the development of nonunion.

The effect of valgus reduction on resistant subtrochanteric femoral non-unions: a single-centre report of twenty six cases

PURPOSE

Re-revision of subtrochanteric non-unions is technically challenging and lacks robust evidence. The results of managing subtrochanteric fractures after multiple failed procedures have rarely been reported in the literature. This study aims to evaluate the effect of valgus reduction on non-united subtrochanteric fractures with single or multiple failed revision surgeries.

METHODS

Twenty-six patients with aseptic subtrochanteric fracture non-union underwent failed single or multiple revision procedures after index fracture fixation surgery between 2011 and 2019. The exclusion criteria were as follows: septic non-union, peri-prosthetic, and pathological fractures. Lateral-based wedge valgus reduction and compression at the non-union site using a valgus-contoured DCS together with decortication, debridement, and bone grafting were used. The main outcome measurement was radiological union, pain, LLD, HHS, and restoration of pre-fracture activities.

RESULTS

The mean follow-up was 4.5 years (range 3 to 7); prior revision surgeries range from two to five and union at 6.5 months (range 3 to 10) and the delayed union in one case and an infected non-union in one case. The mean LLD was 4 cm (range 3 to 5), which improved to 1.5 cm (range 1 to 4) (P-value < 0.001). The mean VAS was 7 (range 6 to 8), and 24 patients achieved painless ambulation without a walking aid after the union. The mean HHS was 40 (range 25 to 65), which improved to 85 (range 55 to 95) (P-value < 001), achieving 15 excellent, ten good, and one poor results.

CONCLUSION

Mechanical optimisation by lateral closing wedge and stable fixation with pre-contoured DCS with biological enhancement resulted in a successful outcome in recalcitrant subtrochanteric non-unions.

3D printing of MOF-reinforced methacrylated gelatin scaffolds for bone regeneration

Scaffolds based on gelatin (Gel) play a crucial role in bone tissue engineering. However, the low mechanical properties, rapid biodegradation rate, insufficient osteogenic activity and lacking anti-infective properties limit their applications in bone regeneration. Herein, the incorporation of ibuprofen (IBU)-loaded zeolitic imidazolate framework-8 (ZIF-8) in a methacrylated gelatin (GelMA) matrix was proposed as a simple and effective strategy to develop the IBU-ZIF-8@GelMA scaffolds for enhanced bone regeneration capacity. Results indicated that the IBU-loaded ZIF-8 nanoparticles with tiny particle sizes were uniformly distributed in the GelMA matrix of the IBU-ZIF-8@GelMA scaffolds, and the IBU-loaded ZIF-8 growing in the scaffolds enabled the controlled and sustained releasing of Zn2+ and IBU in pH = 5.5 over a long period for efficient bone repair and long-term anti-inflammatory activity. Furthermore, the doping of the IBU-loaded ZIF-8 nanoparticles efficiently enhanced the compression performance of the GelMA scaffolds. In vitro studies indicated that the prepared scaffolds presented no cytotoxicity to MC3T3-E1 cells and the released Zn2+ during the degradation of the scaffolds promoted MC3T3-E1 cell osteogenic differentiation. Thus, the drug-loaded ZIF-8 modified 3D printed GelMA scaffolds demonstrated great potential in treating bone defects.

Nanoparticle and Nanotopography-Induced Activation of the Wnt Pathway in Bone Regeneration

Background and Aims: Recent research has focused on developing nanoparticle and nanotopography-based technologies for bone regeneration. The Wingless-related integration site (Wnt) signaling pathway has been shown to play a vital role in this process, in particular in osteogenic differentiation and proliferation. The exact mechanisms by which nanoparticles and nanotopographies activate the Wnt signaling pathway, however, are not fully understood. This review aimed to elucidate the mechanisms by which nanoscale technologies activate the Wnt signaling pathway during bone regeneration. Methods: The terms "Wnt," "bone," and "nano*" were searched on PubMed and Ovid with no date limit. Only original research articles related to Wnt signaling and bone regeneration in the context of nanotopographies, nanoparticles, or scaffolds with nanotopographies/nanoparticles were reviewed. Results: The primary mechanism by which nanoparticles activated the Wnt pathway was by internalization through the endocytic pathway or diffusion through the cell membrane, leading to accumulation of nonphosphorylated β-catenin in the cytoplasm and subsequently downstream osteogenic signaling (e.g., upregulation of runt-related transcription factor 2 [RUNX2]). The specific size of the nanoparticles and the process of endocytosis itself has been shown to modulate the Wnt-β-catenin pathway. Nanotopographies were shown to directly activate frizzled receptors, initiating Wnt/β-catenin signaling. Additional studies showed nanotopographies to activate the Wnt/calcium (Wnt/Ca2+)-dependent and Wnt/planar cell polarity pathways through nuclear factor of activated T cells, and α5β1 integrin stimulation. Finally, scaffolds containing nanotopographies/nanoparticles were found to induce Wnt signaling through a combination of ion release (e.g., lithium, boron, lanthanum, and icariin), which inhibited glycogen synthase kinase 3 beta (GSK-3β) activity, and through similar mechanisms to the nanotopographies. Conclusion: This review concludes that nanoparticles and nanotopographies cause Wnt activation through several different mechanisms, specific to the size, shape, and structure of the nanoparticles or nanotopographies. Endocytosis-related mechanisms, integrin signaling and ion release were the major mechanisms identified across nanoparticles, nanotopographies, and scaffolds, respectively. Knowledge of these mechanisms will help develop more effective targeted nanoscale technologies for bone regeneration. Impact statement Nanoparticles and nanotopographies can activate the Wingless-related integration site (Wnt) signaling pathway, which is essential for bone regeneration. This review has identified that activation is due to endocytosis, integrin signaling and ion release, depending on the size, shape, and structure of the nanoparticles or nanotopographies. By identifying and further understanding these mechanisms, more effective nanoscale technologies that target the Wnt signaling pathway can be developed. These technologies can be used for the treatment of nonunion bone fractures, a major clinical challenge, with the potential to improve the quality of life of millions of patients around the world.

The Impact of Defect Size on Bone Healing in Critical-Size Bone Defects Investigated on a Rat Femur Defect Model Comparing Two Treatment Methods

Critical-size bone defects up to 25 cm can be treated successfully using the induced membrane technique established by Masquelet. To shorten this procedure, human acellular dermis (HAD) has had success in replacing this membrane in rat models. The aim of this study was to compare bone healing for smaller and larger defects using an induced membrane and HAD in a rat model. Using our established femoral defect model in rats, the animals were placed into four groups and defects of 5 mm or 10 mm size were set, either filling them with autologous spongiosa and surrounding the defect with HAD or waiting for the induced membrane to form around a cement spacer and filling this cavity in a second operation with a cancellous bone graft. Healing was assessed eight weeks after the operation using µ-CT, histological staining, and an assessment of the progress of bone formation using an established bone healing score. The α-smooth muscle actin used as a signal of blood vessel formation was stained and counted. The 5 mm defects showed significantly better bone union and a higher bone healing score than the 10 mm defects. HAD being used for the smaller defects resulted in a significantly higher bone healing score even than for the induced membrane and significantly higher blood vessel formation, corroborating the good results achieved by using HAD in previous studies. In comparison, same-sized groups showed significant differences in bone healing as well as blood vessel formation, suggesting that 5 mm defects are large enough to show different results in healing depending on treatment; therefore, 5 mm is a viable size for further studies on bone healing.

Anterior Full-endoscopic Single-port Double Transcorporeal Spinal Cord Decompression for Noncontinuous Two-segment Cervical Spondylotic Myelopathy: A Technical Note

OBJECTIVE

In clinical practice, noncontinuous two-segment spinal cord cervical spondylosis is a particular form of cervical degenerative disease. Traditional anterior open surgery frequently comes with severe trauma, risks, and debatable treatment options. This study aimed to describe for the first time a novel minimally invasive technique, namely, anterior full-endoscopic single-port double transcorporeal spinal cord decompression for the treatment of patients with noncontinuous two-segment cervical spondylotic myelopathy.

METHOD

From February 2020 to May 2021, five patients with noncontinuous two-segment cervical spondylotic myelopathy were treated with anterior full-endoscopic single-port double transcorporeal spinal cord decompression. Two bone channels were established by the trephine through the vertebral body oblique upward and downward to the herniated disc osteophyte complex, and the full-endoscopic system could decompress the spinal cord through the channels. All cases were followed up for over 2 years. The modified Japanese Orthopaedic Association (mJOA) score and visual analogue scale (VAS) score before and after operation and during follow-up were used to evaluate the clinical effectiveness. Radiological examinations, including CT and MRI, were utilized to evaluate the efficacy of spinal cord decompression and bone channel repair.

RESULTS

All operations were successfully completed and the average operation time was 185 min, with no operation-related complications. Compared with the preoperative evaluation, the mJOA score and VAS score were improved at each time point after operation and follow-up. Postoperative CT and MRI scans showed that the intervertebral disc-osteophyte complex was removed through the vertebral bone passage, and the spinal cord was fully decompressed. After 24 months of follow-up, CT and MRI scans showed that the bone channel was almost repaired and healed.

CONCLUSION

Anterior full-endoscopic single-port double transcorporeal spinal cord decompression is an effective minimally invasive technique for noncontinuous two-segment cervical spondylosis. It provides precise and satisfactory spinal cord decompression under endoscopic visualization with minimum trauma.

The local and systemic effects of immune function on fracture healing

The immune system plays an integral role in the regulation of cellular processes responsible for fracture healing. Local and systemic influences on fracture healing correlate in many ways with fracture-related outcomes, including soft tissue healing quality and fracture union rates. Impaired soft tissue healing, restricted perfusion of a fracture site, and infection also in turn affect the immune response to fracture injury. Modern techniques used to investigate the relationship between immune system function and fracture healing include precision medicine, using vast quantities of data to interpret broad patterns of inflammatory response. Early data from the PRECISE trial have demonstrated distinct patterns of inflammatory response in polytrauma patients, which thereby directly and indirectly regulate the fracture healing response. The clearly demonstrated linkage between immune function and fracture healing suggests that modulation of immune function has significant potential as a therapeutic target that can be used to enhance fracture healing.

Surgical Reconstruction of Canine Nonunion Fractures Using Bone Morphogenetic Protein-2-loaded Alginate Microbeads and Bone Allografts

BACKGROUND/AIM

Effective treatment of nonunion fractures is challenging as it requires a biological and mechanical environment to promote sufficient osteogenesis. Herein, we present a case series in which we evaluated the clinical efficacy of bone morphogenetic protein-2 (BMP-2)-loaded alginate microbeads and allografts in two dogs with nonunion fractures.

CASE REPORT

A 3-year-old, 2.3-kg, spayed female Pomeranian (Case 1) presented with intermittent lameness of the left forelimb after radial and ulnar fracture repair 8 weeks prior. A 4-year-old, 4.8-kg, spayed female Pomeranian (Case 2) was referred for non-weight-bearing lameness of the left hindlimb due to implant failure following left tibial fracture repair. Both dogs had atrophic bone ends and no bridging calluses at the fracture site on radiographs, and were diagnosed with nonviable nonunion fractures of the radius/ulna and tibia, respectively. The surgical approach involved implant removal, debridement, and fracture gap reconstruction. BMP-2 was loaded into alginate microbeads for a prolonged release with bone allograft chips in both cases. In Case 1, bead grafts were applied directly at the fracture site, while in Case 2, they were implanted inside a frozen cortical bone allograft as a scaffold to fill the large gap. Postoperative radiography revealed excessive callus formation, early radiographic bone union, and cortical bone remodeling, in line with improved lameness scores. At the final follow-up, gait was improved and the desired bone length and shape were achieved in both cases.

CONCLUSION

Simultaneous use of osteoinductive BMP-2 alginate microbeads and osteoconductive bone allografts yielded functionally and structurally favorable outcomes in canine nonunion fractures, without major complications.

Outcomes of Humerus Nonunion Surgery in Patients With Initial Operative Fracture Fixation

OBJECTIVES

To describe outcomes following humerus aseptic nonunion surgery in patients whose initial fracture was treated operatively and to identify risk factors for nonunion surgery failure in the same population.

METHODS

DESIGN

Retrospective case series.

SETTING

Eight, academic, level 1 trauma centers.

PATIENTS SELECTION CRITERIA

Patients with aseptic humerus nonunion (OTA/AO 11 and 12) after the initial operative management between 1998 and 2019.

OUTCOME MEASURES AND COMPARISONS

Success rate of nonunion surgery.

RESULTS

Ninety patients were included (56% female; median age 50 years; mean follow-up 21.2 months). Of 90 aseptic humerus nonunions, 71 (78.9%) united following nonunion surgery. Thirty patients (33.3%) experienced 1 or more postoperative complications, including infection, failure of fixation, and readmission. Multivariate analysis found that not performing revision internal fixation during nonunion surgery (n = 8; P = 0.002) and postoperative de novo infection (n = 9; P = 0.005) were associated with an increased risk of recalcitrant nonunion. Patient smoking status and the use of bone graft were not associated with differences in the nonunion repair success rate.

CONCLUSIONS

This series of previously operated aseptic humerus nonunions found that more than 1 in 5 patients failed nonunion repair. De novo postoperative infection and failure to perform revision internal fixation during nonunion surgery were associated with recalcitrant nonunion. Smoking and use of bone graft did not influence the success rate of nonunion surgery. These findings can be used to give patients a realistic expectation of results and complications following humerus nonunion surgery.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Results of a simple treatment protocol for aseptic femoral shaft nonunion in 330 patients

INTRODUCTION

Our primary aim of the study was to assess the results of a treatment protocol for aseptic femoral shaft nonunion treated by three techniques - Exchange Nailing (EN), Plate Augmentation (PA), and Exchange Nailing combined with Plate augmentation (NP). The secondary objective was to assess the radiological outcome, duration of surgery (DOS) and need for blood transfusion (BT) in all the three groups.

MATERIALS AND METHODS

We analyzed 330 patients treated for AFNU between Jan 2007 and Dec 2019. Using a simple treatment algorithm, EN, PA and NP were performed in 24,183 and 123 patients respectively. Patients in all the three groups were assessed for radiological-union (union rate and time to union), DOS and BT.

RESULTS

Of these 330 patients, 327 (99 %) patients achieved radiological union at a mean duration of 6.07 months. Union rate is highest with NP followed by PA and EN. The union rate in patients with NP, PA and EN were 100 %, 99.5 % and 91.7 % respectively (p < 0.01). Time to union was lowest for NP followed by PA and EN (p < 0.001).The mean time to union for NP, PA and EN were 3.76, 7.2and 9.21 months respectively (p < 0.001). The mean DOS in minutes for NP, EN and PA was 107, 94 and 82 respectively (p < 0.01). The mean need for BT in the form of packed red blood cells for NP, PA and EN were 1.95, 1.87 and 1.38 units respectively (p < 0.01).

CONCLUSION

Following a simple algorithm to decide treatment protocol on a case-to case basis helps to achieve good results in an optimal time period. When compared with EN and PA, NP is associated with 100 % union rate with least time to union making NP a reasonably effective procedure with a very high success rate.

LEVEL OF EVIDENCE

IV.

Long-Term Outcomes Following Single-Stage Reamed Intramedullary Exchange Nailing in Apparently Aseptic Femoral Shaft Nonunion with Unsuspected Proof of Bacteria

Background: The aim of this study was to evaluate detection rates and risk factors for unsuspected proof of bacteria, as well as clinical and radiologic outcomes following femoral shaft nonunion without clinical signs of infection treated by a single-stage surgical revision procedure including reamed intramedullary exchange nailing. Methods: A retrospective cohort study was performed in a European level I trauma center between January 2015 and December 2022. Fifty-eight patients were included who underwent reamed intramedullary exchange nailing as a single-step procedure for surgical revision of posttraumatic diaphyseal femoral nonunion without any indications of infection in medical history and without clinical signs of local infection. Clinical details of the patients were analyzed and functional and radiologic long-term outcomes were determined. Results: In all patients, with and without proof of bacteria osseous, healing could be observed. The physical component summary of the SF-12 demonstrated significantly better results at least one year after the final surgical revision in case of a negative bacterial culture during exchange nailing. Conclusions: Clinical long-term outcomes demonstrated a trend towards better results following femoral shaft nonunion revision if there was no evidence for the presence of low-grade infected nonunion. In this case, a single-stage surgical procedure may be recommended.

The polymicrobial infection affects the infection recurrence rate (not failure) in treating femoral and tibial bone defects with the Masquelet technique-a comparative retrospective analysis of 54 patients with mono- and polymicrobial infections

INTRODUCTION

This study evaluated whether polymicrobial infection affects reoperation rates due to infection recurrence and treatment failure with the Masquelet technique in infected posttraumatic segmental bone defects of the femur and tibia.

METHODS

 We retrospectively analyzed patients treated between 2012 and 2021 in two trauma referral centers. We evaluated demographic data, injury, treatment, infection recurrence, failures, and bone healing rates according to whether the infection was mono- or polymicrobial. After uni-bivariate analysis between patients with polymicrobial and monomicrobial infection, we identified the variables associated with infection recurrence and failure through multivariate analysis.

RESULTS

 We analyzed 54 patients, 30 (55.55%) with tibial and 24 (44.44%) femoral segmental bone defects, with a mean follow-up of 41.7 ± 15.0 months. Forty-four (81.48%) presented monomicrobial, and 10 (18.51%) polymicrobial infections. Comparatively, the need for soft tissue reconstruction and the infection recurrence rate was significantly higher in patients with polymicrobial infections. There was no significant difference in the failure rate (20 vs. 6.81% p = 0.23). Multivariable logistic regression analysis identified the polymicrobial infection as the only independent variable associated with infection recurrence (Odds Ratio = 11.07; p = 0.0017).

CONCLUSION

 Our analysis suggests that polymicrobial infection is associated with a higher risk of infection recurrence in treating the femur and tibia segmental bone defects with the Masquelet technique. This information can help surgeons to inform patients about this and give them a realistic expectation of the outcome and the possibility of reoperation.

Osteogenic Potential of a Biomaterial Enriched with Osteostatin and Mesenchymal Stem Cells in Osteoporotic Rabbits

Mesoporous bioactive glasses (MBGs) of the SiO2-CaO-P2O5 system are biocompatible materials with a quick and effective in vitro and in vivo bioactive response. MBGs can be enhanced by including therapeutically active ions in their composition, by hosting osteogenic molecules within their mesopores, or by decorating their surfaces with mesenchymal stem cells (MSCs). In previous studies, our group showed that MBGs, ZnO-enriched and loaded with the osteogenic peptide osteostatin (OST), and MSCs exhibited osteogenic features under in vitro conditions. The aim of the present study was to evaluate bone repair capability after large bone defect treatment in distal femur osteoporotic rabbits using MBGs (76%SiO2-15%CaO-5%P2O5-4%ZnO (mol-%)) before and after loading with OST and MSCs from a donor rabbit. MSCs presence and/or OST in scaffolds significantly improved bone repair capacity at 6 and 12 weeks, as confirmed by variations observed in trabecular and cortical bone parameters obtained by micro-CT as well as histological analysis results. A greater effect was observed when OST and MSCs were combined. These findings may indicate the great potential for treating critical bone defects by combining MBGs with MSCs and osteogenic peptides such as OST, with good prospects for translation to clinical practice.

Optimal delivery of endothelial progenitor cells in a rat model of critical-size bone defects

Nonunion and segmental bone defects are complex issues in orthopedic trauma. The use of endothelial progenitor cells (EPCs), as part of a cell-based therapy for bone healing is a promising approach. In preclinical studies, culture medium (CM) is commonly used to deliver EPCs to the defect site, which has the potential for immunogenicity in humans. The goal of this study was to find an effective and clinically translatable delivery medium for EPCs. Accordingly, this study compared EPCs delivered in CM, phosphate-buffered saline (PBS), platelet-poor plasma (PPP), and platelet-rich plasma (PRP) in a rat model of femoral critical-size defects. Fischer 344 rats (n = 35) were divided into six groups: EPC+CM, EPC+PBS, EPC+PPP, EPC+PRP, PPP alone, and PRP alone. A 5 mm mid-diaphyseal defect was created in the right femur and stabilized with a miniplate. The defect was filled with a gelatin scaffold impregnated with the corresponding treatment. Radiographic, microcomputed tomography and biomechanical analyses were performed. Overall, regardless of the delivery medium, groups that received EPCs had higher radiographic scores and union rates, higher bone volume, and superior biomechanical properties compared to groups treated with PPP or PRP alone. There were no significant differences in any outcomes between EPC subgroups or between PPP and PRP alone. These results suggest that EPCs are effective in treating segmental defects in a rat model of critical-size defects regardless of the delivery medium used. Consequently, PBS could be the optimal medium for delivering EPCs, given its low cost, ease of preparation, accessibility, noninvasiveness, and nonimmunogenic properties.

Black Phosphorus Accelerates Bone Regeneration Based on Immunoregulation

A fundamental understanding of inflammation and tissue healing suggests that the precise regulation of the inflammatory phase, both in terms of location and timing, is crucial for bone regeneration. However, achieving the activation of early inflammation without causing chronic inflammation while facilitating quick inflammation regression to promote bone regeneration continues to pose challenges. This study reveals that black phosphorus (BP) accelerates bone regeneration by building an osteogenic immunological microenvironment. BP amplifies the acute pro-inflammatory response and promotes the secretion of anti-inflammatory factors to accelerate inflammation regression and tissue regeneration. Mechanistically, BP creates an osteoimmune-friendly microenvironment by stimulating macrophages to express interleukin 33 (IL-33), amplifying the inflammatory response at an early stage, and promoting the regression of inflammation. In addition, BP-mediated IL-33 expression directly promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), which further facilitates bone repair. To the knowledge, this is the first study to reveal the immunomodulatory potential of BP in bone regeneration through the regulation of both early-stage inflammatory responses and later-stage inflammation resolution, along with the associated molecular mechanisms. This discovery serves as a foundation for the clinical use of BP and is an efficient approach for managing the immune microenvironment during bone regeneration.

The Outcomes of Distraction Osteogenesis over an Intramedullary Nail for the Treatment of Bone Defects in Infectious Nonunions

Objectives

The concurrent utilization of an external fixator and intramedullary nail (IMN) for segment transportation may potentially decrease the duration of external fixator implementation and reduce associated complications. This study aimed to report the outcomes of bone transport utilizing a combination of IMN and Ilizarov frame in a cohort of individuals who had tibia or femur critical-sized bone deficiency resulting from nonunion.

Methods

The present research used a single-arm clinical trial design to enroll a series of patients presenting with critical-sized bone defects resulting from infectious nonunion of the tibia or femur. The study was conducted during the period of 2017-2020 in a referral Orthopedic Surgery Center located in Tehran, Iran. The management of patients with infectious nonunion was carried out through two main stages, including infection eradication and bone transportation. The process of bone healing and segment transportation was evaluated by radiographic assessment throughout the follow-up period.

Results

A total of 39 patients with bone defects in the tibia (19 cases) or femur (20 cases) with a mean age of 31.44 (±11.95, range=18-60) were included in this study. Twenty-nine (74.3%) patients had open fractures. The bone defect exhibited an average size of 6.31 ± 1.95 cm. The mean of the consolidation index (CI) was 0.97 (range=0.51-1.32) mo/cm, and the mean of the external fixator index was 0.67 (range=0.41-1.10). Although the CI was longer in patients with open fracture compared to those with closed fracture, the difference was not statistically significant (P=0.353). After the end of the two-year follow-up, complete union was observed in 35 patients (89.7%).

Conclusion

Intercalary segmental bone transportation using the Ilizarov technique over an IMN, as well as preserving the advantages of the conventional callotasis method, reduces the complications of long-term use of the Ilizarov frame and increases patient adherence to treatment.

In Vivo Evaluation of Bone Regenerative Capacity of the Novel Nanobiomaterial: β-Tricalcium Phosphate Polylactic Acid-co-Glycolide (β-TCP/PLLA/PGA) for Use in Maxillofacial Bone Defects

Maxillofacial bone defects are treated by autografting or filling with synthetic materials in various forms and shapes. Electrospun nanobiomaterials are becoming popular due to their easy placement and handling; combining ideal biomaterials extrapolates better outcomes. We used a novel electrospun cotton-like fiber made from two time-tested bioresorbable materials, β-TCP and PLLA/PGA, to check the feasibility of its application to maxillofacial bone defects through an in vivo rat mandibular bone defect model. Novel β-TCP/PLLA/PGA and pure β-TCP blocks were evaluated for new bone regeneration through assessment of bone volume, inner defect diameter reduction, and bone mineral density. Bioactive/osteoconductivity was checked by scoring the levels of Runt-related transcription factor x, Leptin Receptor, Osteocalcin, and Periostin biomarkers. Bone regeneration in both β-TCP/PLLA/PGA and β-TCP was comparable at initial timepoints. Osteogenic cell accumulation was greater in β-TCP/PLLA/PGA than in β-TCP at initial as well as late phases. Periostin expression was more marked in β-TCP/PLLA/PGA. This study demonstrated comparable results between β-TCP/PLLA/PGA and β-TCP in terms of bone regeneration and bioactivity, even with a small material volume of β-TCP/PLLA/PGA and a decreased percentage of β-TCP. Electrospun β-TCP/PLLA/PGA is an ideal nanobiomaterial for inducing bone regeneration through osteoconductivity and bioresorbability in bony defects of the maxillofacial region.

Physiologically engineered porous titanium/brushite scaffolds for critical-size bone defects: A design and manufacturing study

Repairing critical-size bone defects still represents a critical clinical challenge in the field of trauma surgery. This study focuses on a physiological design and manufacturing of porous composite scaffold (titanium Ti with 10 % mole iron doped brushite DCPD-Fe3+) which can mimic the biomechanical properties of natural cortical bone, specifically for the purpose of repairing critical-size defects. To achieve this, the principle of design of experiments (DOE) was applied for investigating the impact of sintering temperature, mineral ratio, and volume fraction of porosity on the mechanical properties of the fabricated scaffolds. The fabricated scaffolds had open porosity up to 60 %, with pore size approximately between 100 μm and 850 μm. The stiffness of the porous composite scaffolds varied between 3.30 GPa and 20.50 GPa, while the compressive strength ranged from approximately 130 MPa-165 MPa at sintering temperatures equal to or exceeding 1000 °C. Scaffolds with higher porosity and mineral content demonstrated lower stiffness values, resembling natural bone. Numerical simulation was employed by Ansys Workbench to investigate the stress and strain distribution of a critical size defect in mid-shaft femur which was designed to be replaced with the fabricated scaffold. The fabricated scaffolds showed flexible biomechanical behaviour at the bone/scaffold interface, generating lower stress levels and indicating a better match with the femoral shaft stiffness. The experimental and numerical findings demonstrated promising applications for manufacturing a patient-specific bone scaffold for critical and potentially large defects for reducing stress shielding and minimizing non-union risk.

Use of Autologous Bone Graft with Bioactive Glass as a Bone Substitute in the Treatment of Large-Sized Bone Defects of the Femur and Tibia

BACKGROUND

Managing bone defects in non-union surgery remains challenging, especially in cases of large defects exceeding 5 cm in size. Historically, amputation and compound osteosynthesis with a remaining PMMA spacer have been viable and commonly used options. The risk of non-union after fractures varies between 2% and 30% and is dependent on various factors. Autologous bone grafts from the iliac crest are still considered the gold standard but are limited in availability, prompting consideration of artificial grafts.

OBJECTIVES

The aims and objectives of the study are as follows: 1. To evaluate the radiological outcome of e.g., the consolidation and thus the stability of the bone (three out of four consolidated cortices/Lane-Sandhu-score of at least 3) by using S53P4-type bioactive glass (BaG) as a substitute material for large-sized bone defects in combination with autologous bone using the RIA technique. 2. To determine noticeable data-points as a base for future studies.

METHODS

In our clinic, 13 patients received bioactive glass (BaG) as a substitute in non-union therapy to promote osteoconductive aspects. BaG is a synthetic material composed of sodium, silicate, calcium, and phosphate. The primary endpoint of our study was to evaluate the radiological consolidation of bone after one and two years. To assess bone stabilization, we used a modified Lane-Sandhu score, considering only radiological criteria. A bone was considered stabilized if it achieved a minimum score of 3. For full consolidation (all four cortices consolidated), a minimum score of 4 was required. Each bone defect exceeded 5 cm in length, with an average size of 6.69 ± 1.92 cm.

RESULTS

The mean follow-up period for patients without final bone consolidation was 34.25 months, with a standard deviation of 14.57 months, a median of 32.00 months and a range of 33 months. In contrast, patients with a fully consolidated non-union had an average follow-up of 20.11 ± 15.69 months and a range of 45 months. Overall, the mean time from non-union surgery to consolidation for patients who achieved final union was 14.91 ± 6.70 months. After one year, six patients (46.2%) achieved complete bone consolidation according to the Lane-Sandhu score. Three patients (23.1%) displayed evident callus formation with expected stability, while three patients (23.1%) did not develop any callus, and one patient only formed a minimal callus with no expected stability. After two years, 9 out of 13 patients (69.2%) had a score of 4. The remaining four patients (30.8%) without expected stability either did not heal within two years or required a revision during that time.

CONCLUSIONS

Bioactive glass (BaG) in combination with autologous bone (RIA) appears to be a suitable filler material for treating extensive non-unions of the femur and tibia. This approach seems to show non-inferiority to treatment with Tricalcium Phosphate (TCP). To ensure the success of this treatment, it is crucial to validate the procedure through a randomized controlled trial (RCT) with a control group using TCP, which would provide higher statistical power and more reliable results.

Parathyroid hormone stimulates bone regeneration in an atrophic non-union model in aged mice

BACKGROUND

Non-union formation still represents a major burden in trauma and orthopedic surgery. Moreover, aged patients are at an increased risk for bone healing failure. Parathyroid hormone (PTH) has been shown to accelerate fracture healing in young adult animals. However, there is no information whether PTH also stimulates bone regeneration in atrophic non-unions in the aged. Therefore, the aim of the present study was to analyze the effect of PTH on bone regeneration in an atrophic non-union model in aged CD-1 mice.

METHODS

After creation of a 1.8 mm segmental defect, mice femora were stabilized by pin-clip fixation. The animals were treated daily with either 200 mg/kg body weight PTH 1-34 (n = 17) or saline (control; n = 17) subcutaneously. Bone regeneration was analyzed by means of X-ray, biomechanics, micro-computed tomography (µCT) imaging as well as histological, immunohistochemical and Western blot analyses.

RESULTS

In PTH-treated animals bone formation was markedly improved when compared to controls. This was associated with an increased bending stiffness as well as a higher number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and CD31-positive microvessels within the callus tissue. Furthermore, PTH-treated aged animals showed a decreased inflammatory response, characterized by a lower number of MPO-positive granulocytes and CD68-positive macrophages within the bone defects when compared to controls. Additional Western blot analyses demonstrated a significantly higher expression of cyclooxygenase (COX)-2 and phosphoinositide 3-kinase (PI3K) in PTH-treated mice.

CONCLUSION

Taken together, these findings indicate that PTH is an effective pharmacological compound for the treatment of non-union formation in aged animals.

Induced membrane technique versus one-stage autografting in management of atrophic nonunion of long bone in the lower limb: clinical and health burden outcomes

OBJECTIVE

In this study, we aimed to compare the outcomes of the two-stage induced membrane technique (IMT) and one-stage autografting in the treatment of aseptic atrophic nonunion in lower limb long bones.

METHODS

From January 2014 to January 2022, we reviewed all surgically treated long bone nonunion patients, including patients aged 18 years or older with atrophic nonunion, who were either treated with the two-stage induced membrane technique (IMT) or one-stage autografting. Outcome parameters interns of clinical, quality of life and healthcare burden were recorded and retrospectively analysed between the two treatment populations. The follow-up time was at least 1 year.

RESULTS

In total, 103 patients who met the criteria for aseptic atrophic nonunion were enrolled. Among them, 41 (39.8%) patients were treated with two-stage IMT, and 62 (60.2%) patients were treated with one-stage autologous bone grafting. The follow-up time was 12 to 68 months, with an average of 28.4 months. The bone healing rate was comparable in both groups (IMT: 92.7% vs. one-stage grafting: 91.9%, P = 0.089) at 12 months post-operation, and the bone healing Lane-Sandhu score was superior in the IMT group (mean: 8.68 vs. 7.81, P = 0.002). Meanwhile, the SF-12 scores of subjective physical component score (PCS) (mean: 21.36 vs. 49.64, P < 0.01) and mental health component score (MCS) (mean: 24.85 vs. 46.14, P < 0.01) significantly increased in the IMT group, as well as in the one-stage grafting group, and no statistically significant difference was found within groups. However, the total hospital stays (median: 8 days vs. 14 days, P < 0.01) and direct medical healthcare costs (median: ¥30,432 vs. ¥56,327, P < 0.05) were greater in the IMT group, while the complications (nonunion 8, infection 3, material failure 2, and donor site pain 6) were not significantly different between the two groups (17.1% vs. 19.4, P = 0.770).

CONCLUSION

The data indicate that two-stage method of IMT serves as an alternative method in treating atrophic nonunion; however, it may not be a preferred option, in comprehensive considering patient clinical outcomes and healthcare burden. More evidence-based research is needed to further guide clinical decision-making.

Augmentation plate without bone graft in the management of distal tibial diaphyseal non-union

PURPOSE

The objective of this study was to assess the efficacy of augmentation plating with retaining of previous implant in situ in cases of non-united oligotrophic or atrophic aseptic distal tibial diaphyseal and metaphyseal fractures without bone grafting depending on the unified bone healing and non-union theory.

METHODS

Through the period between December 2019 and December 2022, twelve patients with distal third tibial non-unions who were fixed at time of fracture either by intramedullary interlocking nails (seven cases) or by minimally invasive plate osteosynthesis (five cases) were included. Non-union was diagnosed on basis of absence of any healing progression in three months period or absence of fracture healing after six months from index surgery. All patients had oligotrophic or atrophic non-union. Augmentation plating through an anterolateral approach was done on average of 7.25 months after initial surgery (6-9 months). Circumferential exposure of the fracture site and debridement of fibrous tissue were not necessary. No bone grafting was done as no cases had major bone defect.

RESULTS

All patients achieved complete radiological union with a mean time of 21.8 weeks (range 18-30 weeks) that mean full callus formation in all cortices. All patients were walking independently after three months (13weeks) from surgery and returned to work even in cases of absent complete radiological union. No cases had been complicated with wound healing problems (infection or dehiscence). One patient had incomplete ankle dorsiflexion (10°) due to tight calf muscles and one patient had paresthesia on the dorsum of the foot that was not improved at last follow up (one year after surgery).

CONCLUSION

Augmentation plating is a safe and effective option for management of distal tibial diaphyseal nonunion even in cases of oligotrophic or atrophic non-union.

Unbiased gene expression analysis of the delayed fracture healing observed in Zucker diabetic fatty rats

Aims

Impaired fracture repair in patients with type 2 diabetes mellitus (T2DM) is not fully understood. In this study, we aimed to characterize the local changes in gene expression (GE) associated with diabetic fracture. We used an unbiased approach to compare GE in the fracture callus of Zucker diabetic fatty (ZDF) rats relative to wild-type (WT) littermates at three weeks following femoral osteotomy.

Methods

Zucker rats, WT and homozygous for leptin receptor mutation (ZDF), were fed a moderately high-fat diet to induce T2DM only in the ZDF animals. At ten weeks of age, open femoral fractures were simulated using a unilateral osteotomy stabilized with an external fixator. At three weeks post-surgery, the fractured femur from each animal was retrieved for analysis. Callus formation and the extent of healing were assessed by radiograph and histology. Bone tissue was processed for total RNA extraction and messenger RNA (mRNA) sequencing (mRNA-Seq).

Results

Radiographs and histology demonstrated impaired fracture healing in ZDF rats with incomplete bony bridge formation and an influx of intramedullary inflammatory tissue. In comparison, near-complete bridging between cortices was observed in Sham WT animals. Of 13,160 genes, mRNA-Seq analysis identified 13 that were differentially expressed in ZDF rat callus, using a false discovery rate (FDR) threshold of 10%. Seven genes were upregulated with high confidence (FDR = 0.05) in ZDF fracture callus, most with known roles in inflammation.

Conclusion

These findings suggest that elevated or prolonged inflammation contributes to delayed fracture healing in T2DM. The identified genes may be used as biomarkers to monitor and treat delayed fracture healing in diabetic patients.

[Extracorporeal shockwave therapy as an alternative treatment in cases of posttraumatic delayed bone union]

BACKGROUND

Impaired posttraumatic bone healing is a relevant complication of fractures. Usually, the standard treatment is surgical revision. For about 30 years extracorporeal shockwave therapy (ESWT) has emerged as an alternative treatment option with similar consolidation rates but less complications.

OBJECTIVE

This article aims to present our data in context to the current literature MATERIAL AND METHODS: From 2007 to 2016 a total of 97 patients diagnosed with impaired posttraumatic bone healing were treated with ESWT. Clinical and demographic data of this population were retrieved and analyzed retrospectively.

RESULTS

The general consolidation rate was 60.8%. Multiple variables were analyzed. A preinterventional bone gap ≥ 5 mm, initial dislocation > ½ of the bone shaft, nicotine consumption and a long time span from fracture to ESWT (> 6 months) were found as factors which significantly impair bone healing after ESWT.

CONCLUSION

ESWT is a safe and promising alternative treatment option for delayed unions. Regarding risk factors of a poor outcome may be identified before and increase the rate of success.

Sildenafil, a phosphodiesterase-5 inhibitor, stimulates angiogenesis and bone regeneration in an atrophic non-union model in mice

Non-union formation represents a major complication in trauma and orthopedic surgery. The phosphodiesterase-5 (PDE-5) inhibitor sildenafil has been shown to exert pro-angiogenic and pro-osteogenic effects in vitro and in vivo. Therefore, the aim of the present study was to analyze the impact of sildenafil in an atrophic non-union model in mice. After creation of a 1.8 mm segmental defect, mice femora were stabilized by pin-clip fixation. Bone regeneration was analyzed by means of X-ray, biomechanics, photoacoustic and micro-computed tomography (µCT) imaging as well as histological, immunohistochemical and Western blot analyses at 2, 5 and 10 weeks after surgery. The animals were treated daily with either 5 mg/kg body weight sildenafil (n = 35) or saline (control; n = 35) per os. Bone formation was markedly improved in defects of sildenafil-treated mice when compared to controls. This was associated with a higher bending stiffness as well as an increased number of CD31-positive microvessels and a higher oxygen saturation within the callus tissue. Moreover, the bone defects of sildenafil-treated animals contained more tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and CD68-positive macrophages and exhibited a higher expression of the pro-angiogenic and pro-osteogenic markers cysteine rich protein (CYR)61 and vascular endothelial growth factor (VEGF) when compared to controls. These findings demonstrate that sildenafil acts as a potent stimulator of angiogenesis and bone regeneration in atrophic non-unions.

Segmental defect healing in the presence or absence of recombinant human BMP2: Novel insights from a rat model

This study defined and compared the course of native, impaired and growth factor-stimulated bone regeneration in a rat femoral defect model. A mid-diaphyseal defect with rigid internal fixation was surgically created in the right femur of male Fischer rats and serially analyzed over 36 weeks. Native bone regeneration was modeled using a sub-critical, 1 mm size defect, which healed uneventfully. Critical size defects of 5 mm were used to analyze impaired bone regeneration. In a third group, the 5 mm defects were filled with 11 µg of recombinant human bone morphogenetic protein 2 (rhBMP2) impregnated onto an absorbable collagen sponge, modeling its clinical use. Native bone regeneration was characterized by endochondral ossification with progressive remodeling to ultimately resemble intact femora. An endochondral response was also observed under conditions of impaired bone regeneration, but by week 8 medullary capping occurred with fibrofatty consolidation of the tissue within the defect, resembling an atrophic non-union. rhBMP2 treatment was associated with prolonged inflammatory cytokine expression and rapid intramembranous bone formation occurring with reduced expression of cartilage-associated collagens. Between weeks 4 and 36, rhBMP2-treated bones demonstrated decreased trabecular number and increased trabecular separation, which resulted in inferior mechanical properties compared with bones that healed naturally. Clinical Significance: Recombinant human bone morphogenetic protein 2 (rhBMP2) is used clinically to promote healing of long bones. Our data suggest that it drives intramembraneous ossification producing an inferior regenerate that deteriorates with time. Clinical outcomes would be improved by technologies favoring endochondral regenerative ossification.

New insights in lower limb reconstruction strategies

High Energy Musculoskeletal Traumas (HEMTs) represent a relevant problem for healthcare systems, considering the high social costs, and both the high morbidity and mortality. The poor outcomes associated with HEMT are related to the high incidence of complications, including bone infection, fracture malunion and non-union. The treatment of each of these complications could be extremely difficult. Limb reconstruction often needs multiple procedures, rising some questions on the opportunity in perseverate to try to save the affected limb. In fact, theoretically, amputation may guarantee better function and lower complications. However, amputation is not free of complication, and a high long-term social cost has been reported. A comprehensive literature review was performed to suggest possible ways to optimize the limb preservation surgeries of HEMT's complications in order to ameliorate their management.

Enhancement of Scaffold In Vivo Biodegradability for Bone Regeneration Using P28 Peptide Formulations

The field of bone tissue engineering has shown a great variety of bone graft substitute materials under development to date, with the aim to reconstruct new bone tissue while maintaining characteristics close to the native bone. Currently, insufficient scaffold degradation remains the critical limitation for the success of tailoring the bone formation turnover rate. This study examines novel scaffold formulations to improve the degradation rate in vivo, utilising chitosan (CS), hydroxyapatite (HAp) and fluorapatite (FAp) at different ratios. Previously, the P28 peptide was reported to present similar, if not better performance in new bone production to its native protein, bone morphogenetic protein-2 (BMP-2), in promoting osteogenesis in vivo. Therefore, various P28 concentrations were incorporated into the CS/HAp/FAp scaffolds for implantation in vivo. H&E staining shows minimal scaffold traces in most of the defects induced after eight weeks, showing the enhanced biodegradability of the scaffolds in vivo. The HE stain highlighted the thickened periosteum indicating a new bone formation in the scaffolds, where CS/HAp/FAp/P28 75 µg and CS/HAp/FAp/P28 150 µg showed the cortical and trabecular thickening. CS/HAp/FAp 1:1 P28 150 µg scaffolds showed a higher intensity of calcein green label with the absence of xylenol orange label, which indicates that mineralisation and remodelling was not ongoing four days prior to sacrifice. Conversely, double labelling was observed in the CS/HAp/FAp 1:1 P28 25 µg and CS/HAp/FAp/P28 75 µg, which indicates continued mineralisation at days ten and four prior to sacrifice. Based on the HE and fluorochrome label, CS/HAp/FAp 1:1 with P28 peptides presented a consistent positive osteoinduction following the implantation in the femoral condyle defects. These results show the ability of this tailored formulation to improve the scaffold degradation for bone regeneration and present a cost-effective alternative to BMP-2.

The Diamond Concept Enigma: Recent Trends of Its Implementation in Cross-linked Chitosan-Based Scaffolds for Bone Tissue Engineering

An increasing number of publications over the past ten years have focused on the development of chitosan-based cross-linked scaffolds to regenerate bone tissue. The design of biomaterials for bone tissue engineering applications relies heavily on the ideals set forth by a polytherapy approach called the "Diamond Concept". This methodology takes into consideration the mechanical environment, scaffold properties, osteogenic and angiogenic potential of cells, and benefits of osteoinductive mediator encapsulation. The following review presents a comprehensive summarization of recent trends in chitosan-based cross-linked scaffold development within the scope of the Diamond Concept, particularly for nonload-bearing bone repair. A standardized methodology for material characterization, along with assessment of in vitro and in vivo potential for bone regeneration, is presented based on approaches in the literature, and future directions of the field are discussed.

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.

The Cambridge Experience with Lower Limb Long Bone Non-union Following Fixation and the Treatment Algorithm

Aim

Non-unions have been traditionally classified as atrophic, oligotrophic and hypertrophic and their management was primarily dictated by that. In our Unit, we have based our treatment rationale mainly on the stability of the metalwork and the presence of symptoms rather than the radiologic appearance of the non-union or the presence of infection. The aim was to present the treatment algorithm for lower limb long bone non-union following operative fixation.

Materials and methods

All patients treated for a femoral or tibial non-union following fixation between 2014 and 2020 in our unit and with a minimum follow-up of 2 years were included. Non-union was defined as having no evidence of fracture healing in any cortices six months after the index procedure. Union was defined as bridging callus in at least three cortices visualized on at least two orthogonal radiographs. Information retrieved included demographic and fracture characteristics, presence of infection, evidence of metalwork stability and treatment. Outcome measures included union rate, time to union and complications. Data were analysed with the Statistical Program for Social Sciences (SPSS) using contingency tables and linear regression. A p-value of less than 0.05 was considered statistically significant.

Results

Seventy-seven consecutive patients were included in the study. Union was achieved in 91% of the cases, while union was noted in all the patients treated non-operatively. The mean time to union was 14.49 months (9.98). Complications were encountered in 20 of the patients and the most common were docking site non-union and metalwork breakage. Infection was the only factor that affected time to union in a statistically significant manner (p = 0.006).

Conclusion

The results of our study suggest that in cases of long bone non-union following operative fixation using signs of metalwork instability and the presence of clinical symptoms as the main indication for surgical intervention provides a satisfactory outcome. This approach prevented operative management in a large proportion of patients.

Clinical significance

This article presents an algorithmic approach that could aid clinicians in their decision-making in long-bone non-union management.

Level of evidence

Therapeutic level III.

How to cite this article

Poutoglidou F, Krkovic M. The Cambridge Experience with Lower Limb Long Bone Non-union Following Fixation and the Treatment Algorithm. Strategies Trauma Limb Reconstr 2023;18(2):100-105.

Augmented osteosynthesis in fragility fracture

Due to poor bone quality and complexity, some fractures are difficult to treat, with high risk of failure. Moreover, general health is often poor in elderly patients with multiple comorbidity and poor compliance, necessitating perfect first-line management to avoid re-operation. The armamentarium comprises specific internal fixation implants and also complementary methods such as autologous, homologous or heterologous bone graft or bone substitutes with varying mechanical and biological characteristics. Associating these options is what is mean by "augmented fixation". The present review of augmented osteosynthesis addresses the following questions: What are the characteristics of fragility fractures? Fragility fracture is caused by low-energy trauma on bone with poor structural quality and low mineral density. Treatment aims to enable early mobilization and weight-bearing while avoiding mechanical failure of fixation. Prolonged bedrest, loss of mobility and surgical revision are aggravating and sometimes fatal factors in these fragile patients. What are the biological techniques of fixation augmentation in fragility fracture? Autologous or homologous bone graft are the most widely used biological augmentation techniques. They fill spaces and promote osteoconduction and consolidation. Some bone-like phosphocalcic structures are opening up promising lines of research. What are the non-biological techniques of fixation augmentation in fragility fracture? Hydroxyapatite, phosphocalcic cement and acrylic cement are the most widely used synthetic materials. Biological and mechanical effects are variable according to composition, requiring specific implementation. What are the mechanical techniques of fixation augmentation in fragility fracture? There is at present no consensus as to the augmentation techniques to be applied in fragility fracture. Cerclage or complementary plating, or external fixation associated to internal fixation are possibilities. However, the literature consists only of small series reporting surgical techniques specific to a given surgeon or team. When and how should osteosynthesis for fragility fracture be augmented? The choice of augmentation depends on fracture location, comminution, available material and local experience. The more severe the fracture, the more complex the fixation. The approach needs to be adapted to the preoperative planning and the associated mechanical means (plate, complementary cerclage) and prosthetic replacement should be considered in certain joint fractures or fractures close to load-bearing surfaces. LEVEL OF EVIDENCE: V; expert opinion.

Definitive fixation in the first stage of the induced membrane technique for septic segmental bone defects. Why not?

Background

Infected segmental bone defects (I-SBD) are challenging and complex to manage. This study aimed to show the outcomes achieved in I-SBD of the femur and tibia, treated with the induced membrane technique performing a definitive bone stabilization in the first stage.

Methods

We retrospectively reviewed 30 patients with infected non-articular segmental bone defects of the femur (n = 11) and tibia (n = 19), operated consecutively between January 2015 and May 2021. The need for fixation exchange, bone defect length, allo/autograft ratio used, bone healing, reoperation (discriminating between mechanical and infection-related causes), and failure rates (graft resorption or nonunion) were recorded.

Results

Fixation in the first stage was performed with 28 (93.33%) intramedullary nails, ten coated with antibiotic cement, and 2 (6.67%) locked plates. None were removed during the second stage of the technique. The mean length of the bone defects was 5cm (range 3.5-12). The most commonly used allo-/autograft ratio was 50-50. The bone healing rate was 93.33% (n = 28), with a median follow-up of 7 months (range 3-12). The reoperation rate due to mechanical instability was 3.33% (n = 1) and for recurrence of infection was 10.0% (n = 3). The overall failure rate was 6.67% (n = 2). The median follow-up was 42 months (range 12-85).

Conclusion

Masquelet technique appears feasible and effective in treating infected segmental bone defects of the femur and tibia. Definitive fixation at the first stage showed a success rate of 93.33%, with a re-operation rate of 10.0% related to infection.

A 6-bromoindirubin-3'-oxime incorporated chitosan-based hydrogel scaffold for potential osteogenic differentiation: Investigation of material properties in vitro

Effective treatments for critical size bone defects remain challenging. 6-Bromoindirubin-3'-Oxime (BIO), a glycogen synthase kinase 3β inhibitor, is a promising alternative for treatment of these defects since it aids in promoting osteogenic differentiation. In this study, BIO is incorporated into a new formulation of the guanosine diphosphate cross-linked chitosan scaffold to promote osteogenic differentiation. BIO incorporation was confirmed with ¹³C NMR through a novel concentration dependent peak around 41 ppm. The rapid gelation rate was maintained along with the internal structure's stability. The 10 μM BIO dose supported the control scaffold's microstructure demonstrating a suitable porosity and a low closed pore percentage. While pore sizes of BIO incorporated scaffolds were slightly smaller, pore heterogeneity was maintained. A proof-of-concept study with C2C12 cells suggested a dose-dependent response of BIO on early stages of osteogenic differentiation within the scaffold. These results support future work to examine BIO's role on osteogenic differentiation and biomineralization of encapsulated cells in the scaffold for bone regeneration.

Review: cellularity in bone marrow autografts for bone and fracture healing

The use of autografts, as primary cell and tissue source, is the current gold standard approach to treat critical size bone defects and nonunion defects. The unique mixture of the autografts, containing bony compartments and bone marrow (BM), delivers promising results. Although BM mesenchymal stromal cells (BM-MSCs) still represent a major target for various healing approaches in current preclinical research and respective clinical trials, their occurrence in the human BM is typically low. In vitro expansion of this cell type is regulatory challenging as well as time and cost intensive. Compared with marginal percentages of resident BM-MSCs in BM, BM mononuclear cells (BM-MNCs) contained in BM aspirates, concentrates, and bone autografts represent a readily available abundant cell source, applicable within hours during surgical procedures without the need for time-consuming and regulatory challenging cell expansion. This benefit is one reason why autografting has become a clinical standard procedure. However, the exact anatomy and cellularity of BM-MNCs in humans, which is strongly correlated to their unique mode of action and wide application range remains to be elucidated. The aim of this review was to present an overview of the current knowledge on these specific cell types found in human BM, emphasize the contribution of BM-MNCs in bone healing, highlight donor site dependence, and discuss limitations in the current isolation and subsequent characterization procedures. Hereby, the most recent and relevant examples of human BM-MNC cell characterization, flow cytometric analyses, and findings are summarized, with a strong focus on bone therapy.

The decisive early phase of bone regeneration

Bone has a remarkable endogenous regenerative capacity that enables scarless healing and restoration of its prior mechanical function, even under challenging conditions such as advanced age and metabolic or immunological degenerative diseases. However - despite much progress - a high number of bone injuries still heal with unsatisfactory outcomes. The mechanisms leading to impaired healing are heterogeneous, and involve exuberant and non-resolving immune reactions or overstrained mechanical conditions that affect the delicate regulation of the early initiation of scar-free healing. Every healing process begins phylogenetically with an inflammatory reaction, but its spatial and temporal intensity must be tightly controlled. Dysregulation of this inflammatory cascade directly affects the subsequent healing phases and hinders the healing progression. This Review discusses the complex processes underlying bone regeneration, focusing on the early healing phase and its highly dynamic environment, where vibrant changes in cellular and tissue composition alter the mechanical environment and thus affect the signalling pathways that orchestrate the healing process. Essential to scar-free healing is the interplay of various dynamic cascades that control timely resolution of local inflammation and tissue self-organization, while also providing sufficient local stability to initiate endogenous restoration. Various immunotherapy and mechanobiology-based therapy options are under investigation for promoting bone regeneration.

Scaffold Guided Bone Regeneration for the Treatment of Large Segmental Defects in Long Bones

Bone generally displays a high intrinsic capacity to regenerate. Nonetheless, large osseous defects sometimes fail to heal. The treatment of such large segmental defects still represents a considerable clinical challenge. The regeneration of large bone defects often proves difficult, since it relies on the formation of large amounts of bone within an environment impedimental to osteogenesis, characterized by soft tissue damage and hampered vascularization. Consequently, research efforts have concentrated on tissue engineering and regenerative medical strategies to resolve this multifaceted challenge. In this review, we summarize, critically evaluate, and discuss present approaches in light of their clinical relevance; we also present future advanced techniques for bone tissue engineering, outlining the steps to realize for their translation from bench to bedside. The discussion includes the physiology of bone healing, requirements and properties of natural and synthetic biomaterials for bone reconstruction, their use in conjunction with cellular components and suitable growth factors, and strategies to improve vascularization and the translation of these regenerative concepts to in vivo applications. We conclude that the ideal all-purpose material for scaffold-guided bone regeneration is currently not available. It seems that a variety of different solutions will be employed, according to the clinical treatment necessary.

A New Osteogenic Membrane to Enhance Bone Healing: At the Crossroads between the Periosteum, the Induced Membrane, and the Diamond Concept

The lack of viability of massive bone allografts for critical-size bone defect treatment remains a challenge in orthopedic surgery. The literature has reviewed the advantages of a multi-combined treatment with the synergy of an osteoconductive extracellular matrix (ECM), osteogenic stem cells, and growth factors (GFs). Questions are still open about the need for ECM components, the influence of the decellularization process on the latter, the related potential loss of function, and the necessity of using pre-differentiated cells. In order to fill in this gap, a bone allograft surrounded by an osteogenic membrane made of a decellularized collagen matrix from human fascia lata and seeded with periosteal mesenchymal stem cells (PMSCs) was analyzed in terms of de-/recellularization, osteogenic properties, PMSC self-differentiation, and angiogenic potential. While the decellularization processes altered the ECM content differently, the main GF content was decreased in soft tissues but relatively increased in hard bone tissues. The spontaneous osteogenic differentiation was necessarily obtained through contact with a mineralized bone matrix. Trying to deepen the knowledge on the complex matrix-cell interplay could further propel these tissue engineering concepts and lead us to provide the biological elements that allow bone integration in vivo.