Non-union: Indications for external fixation

Magnetic resonance imaging quality in the context of a knee-spanning external fixator placed inside the MR bore: a literature review

After emergent assessment of potentially limb-threatening injuries in knee dislocation or multi-ligament knee injury patients, magnetic resonance imaging is necessary to visualize ligamentous structures and plan for soft tissue repair. However, the application of a knee-spanning external fixator may introduce artifact and reduce overall image quality, which can limit the evaluation of soft tissue injury. As a result, the utility of MRI in the context of a knee-spanning external fixator has been called into question. Signal-to-noise ratio, contrast-to-noise ratio, and qualitative scales have been used to assess image quality of MRI in the context of a knee-spanning external fixator. Despite the potential for artifact, studies have demonstrated that useful diagnostic information may be obtained from MRI in the presence of an external fixator. This review examines the general principles of anatomical assessment, magnetic field strength, device composition and design, radiofrequency coil use, and MRI sequences and artifact reduction as they pertain to MRI in the presence of a knee-spanning external fixator.

Perspectives and institutional policies on patient safety and image quality regarding the use of knee-spanning external fixators in MRI: A survey study of the Society of Skeletal Radiology

OBJECTIVE

Concerns regarding patient safety and image quality have made the use of knee-spanning external fixators in MRI a challenging clinical scenario. The purpose of our study was to poll practicing musculoskeletal radiologists on their personal experiences regarding the use of knee-spanning external fixators in MRI in an effort to consolidate practice trends for the radiologists' benefit.

METHODS

A 27-item survey was created to address the institutional use, safety, adverse events, quality, and perspectives of the radiologist related to MRI of an externally fixated knee. The survey was distributed to 1739 members of the Society of Skeletal Radiology.

RESULTS

A total of 72 members of the Society of Skeletal Radiology completed the survey. Most notably, 40 of 72 (55.56%) respondents are permitted to place a knee-spanning external fixator inside the MR bore at their institution, while19 of 72 (26.39%) respondents are not permitted to do so. Fourteen of 32 (43.75%) respondents have institutional guidelines for safely performing an MRI of an externally fixated knee. Twenty-five of 32 (78.13%) respondents are comfortable permitting an MRI of an externally fixated knee.

CONCLUSION

We found a general lack of consensus regarding the decision to scan a patient with a knee-spanning external fixator in MRI. Many institutions lack safety guidelines, and providers rely upon a heterogeneous breadth of resources for safety information. A re-examination of the FDA device labeling nomenclature and expectations of the individual manufacturers may be needed to bridge this gap and help direct management decisions placed upon the provider.

Metacarpal and Phalangeal Nonunions

The majority of phalangeal and metacarpal fractures will proceed to union when appropriately treated. However, when a nonunion does occur, it can lead to significant functional impairment for patients and societal costs. Operative intervention is typically required in these cases, but the technique can vary depending on each individual patient scenario. This article provides an overview of nonunions of the metacarpals and phalanges in the hand, including incidence, risk factors, current treatment options, and postoperative care.

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.

Staphylococcal enterotoxin C as a novel strategy for treating lumbar spondylolysis in adolescents: Description of technique

Lumbar spondylolysis is one of the most common causes of low back pain and primarily affects children and adolescents. Traditional posterior lumbar fixation and interbody fusion surgery has always been the most effective method to treat spondylolysis. However, traditional surgical management has limitations of large trauma, complex operation, high cost, postoperative biomechanical deterioration, and resulting complications. In order to avoid the trauma and complications of surgical treatment, and reduce the cost of treatment. Based on the successful clinical experience of using staphylococcal enterotoxin C (SEC) to treat nonunion after a limb fracture, we identified a minimally invasive method to effectively treat lumbar spondylolysis. A novel minimally invasive therapeutic approach is presented herein of an SEC injection guided by C-arm fluoroscopy to treat lumbar spondylolysis. We describe a novel technique applied in a patient with lumbar spondylolysis, who showed significantly improved low back pain symptoms and a computed tomography scan, including osseous fusion of the bilateral isthmus at L4 after SEC therapy. This is the first reported case description of using an SEC injection to treat lumbar spondylolysis with a successful clinical outcome.

[Therapy of Humeral Shaft Fractures]

Humeral shaft fractures are a rare but challenging entity of injuries of the upper extremity. Despite all advances in the past decades - including improved imaging, adjusted surgical techniques and new implant designs - the treatment of humeral shaft fractures and especially the treatment choice remains challenging. Treatment options need to be evaluated individually under consideration of fracture morphology, soft tissue and potential neurological damage as well as patient-specific factors (i.e., age, comorbidities). Moreover, the risk of common complications such as radial nerve palsy, infection, non-union and malrotation needs to be evaluated in order to facilitate the best possible therapy for each patient. The regular available treatment options include conservative (cast, brace, etc.) and surgical measures (ante- and retrograde nailing, angle-stable plate osteosynthesis). Furthermore, (temporary) external fixation remains an option in emergency and complicative cases. However, none of the aforementioned options have proven a superior gold standard. This review evaluates the currently available treatment options and their individual advantages as well as the probability of possible complications and is aiming to supply a guide for individual treatment choice.

Patient Safety in MRI with the Use of a Joint-Spanning External Fixator for Knee Dislocation: A Critical Analysis Review

» Universal safety guidelines for the use of a knee-spanning external fixator in magnetic resonance imaging (MRI) are unlikely to be established considering the high variability in device construct configurations.» Per the US Food and Drug Administration, manufacturers are to provide parameters for safe MRI scanning for "MR Conditional" devices; however, such labeling may be limited in detail. Physicians should reference manufacturer labels as a starting point while making an educated clinical decision.» Scanning of a knee-spanning external fixator inside the MR bore has been safely demonstrated in previous studies, although with small sample sizes.» When considering MRI in a patient treated with a knee-spanning external fixator, physicians should use all available resources and coordinate with their medical team to make a clinically reasonable decision contrasting patient benefit vs. potential harm.

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.

Is human immunodeficiency virus a risk factor for the development of nonunion?-a case-control study

Objective

Human immunodeficiency virus (HIV) infection has been suggested to be associated with an increased risk of the development of nonunion after a fracture. This prospective matched case-control study in South Africa investigated common risk factors, including HIV status, that influence the development of a nonunion after a femur or tibia fracture.

Methods

Adult participants (cases) with established nonunions of the femur or tibia shaft were recruited over a 16-month period, between December 2017 and April 2019. They were matched for (1) age; (2) sex; (3) fracture site; and (4) fracture management type, with "control" participants who progressed to fracture union within 6 months of injury. All participants were tested for HIV. Multivariable logistic regression models were constructed to investigate associations between known risk factors for the development of nonunion and impaired fracture healing.

Results

A total of 57 cases were matched with 57 "control" participants (44/57 male, 77.2% vs. 13/57 female, 22.8%, median age 36 years). HIV status was not associated with the development of nonunion after the management of tibia and femur fractures, on both univariate (odds ratio, 0.40; confidence interval, 0.10-1.32; P = 0.151) or multivariable (odds ratio, 0.86; confidence interval, 0.18-3.73; P = 0.831) analysis. No other confounding factors were shown to have any statistically significant impact on the odds of developing nonunion in this study cohort.

Conclusion

This study demonstrates that HIV does not seem to increase the risk of the development of nonunion and HIV-positive individuals who sustain a fracture can be managed in the same manner as those who are HIV negative.

Comparison of internal and external fixation after debridement in the Masquelet technique for Cierny-Mader type IV tibial post-traumatic osteomyelitis

OBJECTIVE

To compare the effect of internal fixation vs. external fixation after debridement in stage I of the Masquelet technique for Cierny-Mader (C-M) type Ⅳ chronic post-traumatic tibial osteomyelitis.

METHODS

This retrospective observational study included patients with tibial osteomyelitis who underwent staged treatment with the Masquelet technique between January 2016 and June 2020 at the 920 Hospital of Joint Logistic Support Force of the PLA. The patients were grouped according to the fixation they received after stage I. Infection recurrence, time to radiological bone healing and full weight-bearing, self-rating anxiety scale (SAS) score, Hospital for Special Surgery (HSS) Knee Score, and American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score were compared.

RESULTS

Sixty-three patients were included (50 males and 13 females). There were 40 and 23 patients with internal and external fixation, respectively. There were no significant differences between the two groups regarding the preoperative and intraoperative data (all P>0.05). After stage I operation, the infection control rates were 85.0% and 82.6% in the internal and external fixation groups (P=0.803), and these rates were 92.5% and 95.7% after stage II (P=0.621). There were no differences in the SAS scores (P=0.278), time to radiological union (P=0.795), time to full weight-bearing (P=0.725), AOFAS scores (P=0.302), HSS scores (P=0.085), and complication rates (P=0.593). There were 27 times complications in 19 patients, with an incidence of 42.9%, without significant differences between groups.

CONCLUSION

There were no differences between the two fixation methods after debridement in stage I of the Masquelet technique for C-M type Ⅳ chronic post-traumatic tibia osteomyelitis.

A scoping review of operative and non-invasive management in the treatment of non-unions

INTRODUCTION

Non-union occurs when a fracture fails to adequately heal, and requires additional intervention to achieve union. The purpose of this scoping review is to provide a high-level overview of the existing non-union management literature. This review aims to highlight the current literature on non-union management, as well as identify key areas that require future research to provide a better understanding of potential non-union management strategies.

METHODS

This study utilized the scoping review framework from Arksey and O'Malley All relevant literature on non-union management was systematically searched for within the OVID Medline, OVID Embase, and Web of Science databases. As a scoping review, this study aimed to identify the high-level trends in non-union literature. This was assessed through a visual and numerical summary of the general themes in non-union literature, as well as the timeline in which these trends have occurred.

RESULTS

The literature search identified 8081 articles, of which 2210 articles were included. There is a large body of evidence for various surgical treatment options for non-union. The literature suggests healing rates between 80 and 100 percent for commonly utilized surgical procedures, such as plating with bone graft for long bones. Despite these beneficial healing rates, the requirement of a surgery creates a large socioeconomic burden. The possibility for bone growth stimulator (BGS) options to achieve non-union healing rates in a similar realm as surgical options suggests that the use of a BGS may be a beneficial option prior to surgical intervention, as this would potentially reduce the number of patients who would otherwise require surgery.

CONCLUSION

A large body of evidence exists on non-union management, which is largely comprised of case series and reports. The most commonly assessed non-unions include the tibia, wrist, and femur. Bone grafting, plating, and nailing are the most investigated treatment options. BGS are a non-operative treatment options for non-union that provide similar healing rates to surgical options in certain indications within initial observational data. BGS are a potential option for non-operative management of non-unions to reduce socioeconomic burdens of surgical intervention, with a need for further high-quality investigation in this therapeutic area.

Osteoporosis treatment by mesenchymal stromal/stem cells and their exosomes: Emphasis on signaling pathways and mechanisms

Osteoporosis is the loss of bone density, which is one of the main problems in developed and developing countries and is more common in the elderly. Because this disease is often not diagnosed until a bone fracture, it can become a life-threatening disease and cause hospitalization. With the increase of older people in a population, this disease's personal and social costs increase year by year and affect different communities. Most current treatments focus on pain relief and usually do not lead to bone tissue recovery and regeneration. But today, the use of stem cell therapy is recommended to treat and improve this disease recovery, which helps restore bone tissue by improving the imbalance in the osteoblast-osteoclast axis. Due to mesenchymal stromal/stem cells (MSCs) characteristics and their exosomes, these cells and vesicles are excellent sources for treating and preventing the progression and improvement of osteoporosis. Due to the ability of MSCs to differentiate into different cells and migrate to the site of injury, these cells are used in tissue regenerative medicine. Also, due to their contents, the exosomes of these cells help regenerate and treat various tissue injuries by affecting the injury site's cells. In this article, we attempted to review new studies in which MSCs and their exosomes were used to treat osteoporosis.

A Comparative Study of Treatment With External Fixator Versus Antibiotic Coated Intramedullary Nail in Infected Non-union Long Bones

Introduction: Infected non-union of bones shows problems in providing stability and controlling the infection. The treatment comprises debridement with or without the use of antibiotic cement and achieving stability by either external or internal fixation with or without bone grafting. The use of antibiotic-impregnated cement-coated intramedullary nailing gives stability and treats the infection, thereby permitting early mobilization. External fixation is a definitive mode of fracture stabilization indicated in cases of infected non-unions of the humerus, tibia, and juxta-articular bone. The present study was conducted to compare the results of management of infected non-union long bones treated with an external fixator (Ilizarov and Limb Reconstruction System (LRS)) and vancomycin-coated intramedullary nail.

Materials and method: The present prospective study was conducted on 40 study subjects aged >18 years, and were randomly divided using the alternative method into two groups. Group A: 20 Patients were treated with antibiotic-coated intramedullary interlocking nail (ACIIN). Group B: 20 patients were treated with the external fixator (LRS/Ilizarov). All patients were then evaluated post-operatively using laboratory investigations, and for any sign of inflammation or infection. Results were evaluated using association for the study and application of methods of Ilizarov (ASAMI) scoring system. Data were analyzed using the Statistical Package for Social Sciences (SPSS) version 20 (IBM Corp., Armonk, NY, USA).

Results: It was observed that 80.0% of patients in Group A, and 70% of subjects in Group B showed bony union, revealing a statistically significant (p-value<0.05) difference. Infection control, limb length discrepancy, and deformity were also assessed in both groups. Bone and functional outcomes were assessed using the ASAMI score in both groups. In LRS/Ilizarov, it was observed that 55% of subjects had no infection, 15% showed loosening, and 30% had an infection.

Conclusion: The ACIIN should not be used for bone defects more than 4 cm as it does not achieve stability and for these cases, procedures like external fixators (Ilizarov and LRS) should be used. Antibiotic-coated nail eliminated the complications of the external fixators like pin loosening, and pin infections and was technically less demanding. In our study, stiffness of adjacent joints was more in external fixators (LRS/Ilizarov) than ACIIN.

A novel bone graft technique combined with plating for aseptic recalcitrant long bone nonunion

Background

To evaluate the outcomes and efficacy of a new technique of autogenous iliac crest bone grafting combined with locking compression plate (LCP) vertical fixation for aseptic recalcitrant long bone nonunion.

Methods

From July 2010 to September 2020, 36 aseptic recalcitrant long bone nonunions were treated with a bone-forming channel technique and internal LCP fixation. All the patients had received one or more failed treatments. The injury mechanism, nonunion type and duration, and prior treatments were recorded pre-operation. The routine treatment process included nonunion area exposure, previous implant removal, sclerotic bone debridement, LCP fixation, bone-forming channel creation, and iliac bone grafting, and a second LCP fixation when required. At follow-up, X-ray images were obtained to assess bone healing and implant failure. Visual analog scale (VAS), fracture site stability, limb function, activity, muscle strength, limb length, and complications were recorded.

Results

A total of 34 patients (24 males and 10 females) were finally enrolled, with a mean age of 49.8 ± 12.3 years. At a mean follow-up of 35.6 ± 22.0 months, 32 patients displayed bone union, with a healing rate of 94.1% and mean union time of 6.8 ± 2.4 months. The VAS score was 0.7 ± 1 at the final follow-up. The functional results showed that 19 patients were excellent, 11 patients were good, 2 patients were poor, and 2 patients did not heal.

Conclusion

Bone-forming channel technique combined with LCP vertical fixation is an excellent option to treat recalcitrant long bone nonunion.

Level of evidence

Therapeutic Level IV.

High Rate of Radiographic Union at the Fibular Osteotomy Site With No Complications After an Acute Oblique Osteotomy and Ligation Procedure to Shorten the Fibula in High Tibial Osteotomy

Background:

A fibular shortening osteotomy is needed to perform lateral closing-wedge high tibial osteotomy (LCW-HTO). To achieve this shortening, we have recently developed an acute oblique osteotomy and ligation (AO/L) procedure for the center of the fibular shaft, based on the AO procedure.

Purpose:

To compare the 2-year follow-up outcomes between the AO/L procedure and the AO procedure.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A prospective comparative cohort study was conducted involving 83 patients (83 knees) who underwent shortening osteotomy of the fibula in LCW-HTO between April 2017 and March 2019. The first consecutive 41 knees (AO group) underwent fibular osteotomy with the AO procedure. The remaining 42 knees (AO/L group) underwent fibular osteotomy with the AO/L procedure. All of the patients were evaluated for at least 2 years postoperatively via clinical and radiological assessments. To determine the time needed for complete union at the osteotomy site, we evaluated the radiographs using a radiographic union score for tibial fractures, which was modified for fibular osteotomy. Comparison of outcomes between the 2 groups was performed using the Student t test for continuous variables and the Mann-Whitney U test or Fisher exact test for discrete variables.

Results:

Around the fibular osteotomy site, no perioperative complications were found in either group. The radiographic union score was significantly higher in the AO/L group than in the AO group (P < .0001 at 2, 3, and 6 months; P = .0290 at 12 and 24 months). The union rate at the fibular osteotomy site was significantly higher in the AO/L group (97.6%) than in the AO group (82.9%) at 12 months (P = .0290).

Conclusion:

The AO/L procedure significantly accelerated the formation of bridging callus at the fibular osteotomy site and provided a significantly higher union rate compared with the AO procedure. Both AO/L and AO procedures were free from perioperative complications. These results suggest that the AO/L procedure is clinically useful as an osteotomy procedure to shorten the fibula in LCW-HTO.

An engineering review of external fixators

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Mechanical stability plays a key role in the effectiveness of external fixators.

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Strength and stiffness are the main factors which contributes towards stability.

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Modified configurations of linear, circular and hybrid fixators are investigated.

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Light weight composite materials are gradually replacing traditional metallic alloys.

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Existing research gaps in further optimizing external fixators are identified.

External Fixators are a common technique used to treat a variety of issues related to bones, predominantly due to its non-intrusive nature and versatility in terms of form and materials. While it is mainly used to treat open fractures, its other uses include limb lengthening, deformity correction, bone grafting, compression of non-unions and stabilization of dislocations. Its earliest use dates as far back as 400 BCE and has undergone significant improvements, focusing on both customization and optimization. These two aspects highlight the significance of complementing the orthopaedic requirements with engineering knowledge and its applications. Hence, this review paper aims to conduct an examination of recent developments of external fixators with a special focus on its structure, the usage of materials and biomechanical investigations using experimental and numerical techniques. The paper presents the existing level of engineering knowledge with regards to these aspects and identifies research gaps, which can improve the quality of the commonly used external fixators.

Lower limb reconstruction involving osteosynthesis material: A retrospective study on propeller flaps outcomes

INTRODUCTION

Reconstruction of soft tissue defects in lower limb fractures requiring internal fixation remains a challenging scenario with the optimal surgical treatment still debated. This study aims to recommend, and eventually redefine, surgical indications for propeller flaps reconstruction in the distal lower limb, with a particular focus on the presence or not of metalwork.

METHODS

A retrospective study of lower limb soft tissue reconstructions performed between January 2015 and July 2018 was carried out including all patients treated with a propeller perforator flap (PPF) with at least 6-month follow-up. Patients were further divided in 2 groups depending on the presence of metalwork fixation beneath the flap (F group, propeller on Framework; NF group, propeller with No-Framework).

RESULTS

21 patients were retained (F group, 11 patients; NF group, 10 patients). There were no significant differences between the two groups in age, BMI, ASA scores, comorbidities or defect size. There was a statistically significant difference between the groups (p<0.05) in the cumulative hospital stay with a mean cumulative hospital stay of 22 ± 9 days in the F group and 12 ± 8 days in NF group. Failures were higher where PPF were used to cover hardware material, with 3 patients requiring a major secondary procedure in F group versus 1 patient in NF group.

CONCLUSION

The presence of underlying metalwork significantly reduced the margin for small, day-case revision procedures such as flap readvancement or STSG. This study emphasizes clinical intuition that whilst PPF are a useful and elegant tool in lower limb reconstruction, their use should be limited when underlying metalwork is present.

Fracture nonunion in long bones: A literature review of risk factors and surgical management

Nonunion following a long bone fracture causes considerable morbidity when it occurs. Risk factors depend on specific fractures but there is a complex interplay of injury severity, comorbidities, patient medication and infection. The majority of nonunions occur after long bone fractures with the tibia, femur, forearm, humerus and clavicle predominating. Despite interest in the biological augmentation of fracture healing, the majority of nonunions can be effectively managed with conventional surgical techniques. In this review we present a review of risk factors for nonunion and the outcome following surgical management.

Mesenchymal Stem Cells as a Cornerstone in a Galaxy of Intercellular Signals: Basis for a New Era of Medicine

Around 40% of the population will suffer at some point in their life a disease involving tissue loss or an inflammatory or autoimmune process that cannot be satisfactorily controlled with current therapies. An alternative for these processes is represented by stem cells and, especially, mesenchymal stem cells (MSC). Numerous preclinical studies have shown MSC to have therapeutic effects in different clinical conditions, probably due to their mesodermal origin. Thereby, MSC appear to play a central role in the control of a galaxy of intercellular signals of anti-inflammatory, regenerative, angiogenic, anti-fibrotic, anti-oxidative stress effects of anti-apoptotic, anti-tumor, or anti-microbial type. This concept forces us to return to the origin of natural physiological processes as a starting point to understand the evolution of MSC therapy in the field of regenerative medicine. These biological effects, demonstrated in countless preclinical studies, justify their first clinical applications, and draw a horizon of new therapeutic strategies. However, several limitations of MSC as cell therapy are recognized, such as safety issues, handling difficulties for therapeutic purposes, and high economic cost. For these reasons, there is an ongoing tendency to consider the use of MSC-derived secretome products as a therapeutic tool, since they reproduce the effects of their parent cells. However, it will be necessary to resolve key aspects, such as the choice of the ideal type of MSC according to their origin for each therapeutic indication and the implementation of new standardized production strategies. Therefore, stem cell science based on an intelligently designed production of MSC and or their derivative products will be able to advance towards an innovative and more personalized medical biotechnology.

Mesenchymal stem cell exosomes in bone regenerative strategies-a systematic review of preclinical studies

The ability of bone for regeneration has long been recognized. However, once beyond a critical size, spontaneous regeneration of bone is limited. Several studies have focused on enhancing bone regeneration by applying mesenchymal stromal/stem cells (MSCs) in the treatment strategies. Despite the therapeutic efficacy of MSCs in bone regeneration, cell-based therapies are impeded by several challenges in maintaining the optimal cell potency and viability during expansion, storage, and final delivery to patients. Recently, there has been a paradigm shift in therapeutic mechanism of MSCs in tissue repair from one based on cellular differentiation and replacement to one based on secretion and paracrine signaling. Among the broad spectrum of trophic factors, extracellular vesicles ​particularly the exosomes have been reported to be therapeutically efficacious in several injury/disease indications, including bone defects and diseases. The current systematic review aims to summarize the results of the existing animal studies which were conducted to evaluate the therapeutic efficacy of MSC exosomes for bone regeneration. Following the Preferred Reporting Items for Systematic Reviews and Meta-analysis ​guidelines, the PubMed and The Cochrane Library database were searched for relevant controlled preclinical animal studies. A total of 23 studies were identified, with the total sample size being 690 rats or mice and 38 rabbits. Generally, MSC exosomes were found to be efficacious for bone regeneration in animal models of bone defects and diseases such as osteonecrosis and osteoporosis. In these studies, MSC exosomes promoted new bone formation with supporting vasculature ​and displayed improved morphological, biomechanical, and histological outcomes, coupled with positive effects on cell survival, proliferation, and migration, osteogenesis, and angiogenesis. Unclear-to-low risk in bias and incomplete reporting in the primary studies highlighted the need for standardization in outcome measurements and reporting. Further studies in large animal models to establish the safety and efficacy would provide useful information on guiding the design of clinical trials.

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Therapeutic efficacy of MSC exosomes in bone regeneration was studied in 23 studies.

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MSC exosomes are therapeutically efficacious in bone regeneration.

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MSC exosomes improve morphological, biomechanical, and histological outcomes.

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MSC exosomes promote a multifaceted mechanism in bone regeneration.

Epidemiology, Clinical Assessments, and Current Treatments of Nonunions

PURPOSE OF REVIEW

The failure of bony union following a fracture, termed a fracture nonunion, has severe patient morbidity and economic consequences. This review describes current consensuses and future directions of investigation for determining why, detecting when, and effective treatment if this complication occurs.

RECENT FINDINGS

Current nonunion investigation is emphasizing an expanded understanding of the biology of healing. This has led to assessments of the immune environment, multiple cytokines and morphogenetic factors, and the role of skeletogenic stem cells in the development of nonunion. Detecting biological markers and other objective diagnostic criteria is also a current objective of nonunion research. Treatment approaches in the near future will likely be dominated by the development of specific adjunct therapies to the nonunion surgical management, which will be informed by an expanded mechanistic understanding of nonunion biology. Current consensus among orthopedists is that improved diagnosis and treatment of nonunion hinges first on discoveries at the bench side with later translation to the clinic.