Preclinical therapies to prevent or treat fracture non-union: A systematic review

Enabling adenosine signaling to promote aged fracture healing

Bone fractures and related complications are a significant concern for older adults, particularly with the growing aging population. Therapeutic interventions that promote bone tissue regeneration are attractive for geriatric fracture repair. Extracellular adenosine plays a key role in bone homeostasis and regeneration. Herein, we examined the changes in extracellular adenosine with aging and the potential of local delivery of adenosine to promote fracture healing using aged mice. Extracellular adenosine level was found to be significantly lower in aged bone tissue compared to young mice. Concomitantly, the ecto-5'-nucleotidase CD73 expression was also lower in aged bone. Local delivery of adenosine using injectable, in situ curing microgel delivery units yielded a pro-regenerative environment and promoted fracture healing in aged mice. This study offers new insights into age-related physiological changes in adenosine levels and demonstrates the therapeutic potential of adenosine supplementation to circumvent the compromised healing of geriatric fractures.

Development of a novel rat long-bone nonunion model and efficacy evaluation of a prostaglandin EP4 selective agonist (AKDS001) combined with iliac bone grafting

Aims

Nonunion occurs when a fracture fails to heal permanently, often necessitating surgical intervention to stimulate the bone healing response. Current animal models of long-bone nonunion do not adequately replicate human pathological conditions. This study was intended as a preliminary investigation of a novel rat nonunion model using a two-stage surgical intervention, and to evaluate the efficacy of a selective prostaglandin E2 receptor 4 agonist (AKDS001) as a novel nonunion therapeutic agent compared with existing treatments.

Methods

Initially, Sprague-Dawley rats underwent intramedullary Kirschner wire (K-wire) fixation of a femoral fracture with the interposition of a 2 mm-thick silicon disc. After three weeks, the silicon disc was removed, and the intramedullary K-wire was replaced with plate fixation while maintaining the 2 mm defect. Contrary to the control group (1) that received no treatment, the following therapeutic interventions were performed at injury sites after freshening: (2) freshening group: no grafting; (3) iliac bone (IB) group: IB grafting; (4) AKDS group: AKDS001-loaded microspheres (MS) combined with IB (0.75 mg/ml); and (5) bone morphogenetic protein (BMP) group: grafting of a BMP-2-loaded collagen sponge (10 μg; 0.10 mg/ml). After six weeks, micro-CT (μCT) and histological analysis was performed.

Results

In the control group, the radiological union rate was 0%, and histological findings showed that fracture sites comprised fibrous scar tissue, resembling the histology of human nonunion. The union rates in the freshening, IB, AKDS, and BMP groups were 16.7%, 0%, 62.5%, and 50.0%, respectively. The AKDS group demonstrated a significantly higher union rate than the IB group (p = 0.026). μCT and histological analysis indicated that the quality of newly formed bone was superior in the AKDS group than in the BMP group.

Conclusion

We developed a novel long-bone nonunion model. The co-therapy of AKDS001-MS and IB grafting presents a promising new treatment for nonunion.

A multi-centre, participant-blinded, randomized, 3-year study to compare the efficacy of Virtual Surgical Planning (VSP) to Freehand Surgery (FHS) on bony union and quality of life outcomes for mandibular reconstruction with fibular and scapular free flaps: study protocol for a randomized phase II/III trial

BACKGROUND

Advanced head and neck malignancies with underlying bony involvement often require aggressive oncological resection of large segments of the oral cavity including the mandible. These patients require vascularized donor osseous free tissue transfer to reconstruct significant defects. Traditionally, the donor bone is harvested on its vascular supply and shaped to the defect in a free hand fashion (FHS). However, virtual surgical planning (VSP) has emerged as a method to optimize reconstructive outcomes and decrease operative time. The goals of this study are to assess superiority of VSP to FHS by comparing bony union rates at 12 months, short and long-term complication rates, reconstruction accuracy, quality of life (QOL), functional outcomes, and economic analysis.

METHODS

This is a multicenter phase II/III study randomizing four hundred twenty head and neck patients undergoing mandibulectomy in a 1:1 ratio between VSP and FHS. Intention-to-treat analysis will be performed for patients enrolled but unable to undergo VSP-aided reconstruction. The primary endpoint is bony-union rates at 1 year post-operatively. Secondary outcomes include complication rates, QOL, functional outcomes, and economic burden.

DISCUSSION

This study will provide an assessment of two different surgical approaches to the reconstructive methods of mandible defects using fibular or scapular free flaps on bony-union rates, complications, QOL and economics.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT05429099. Date of registration: June 23, 2022. Current version: 1.0 on March 6, 2024.

Ozone therapy in musculoskeletal medicine: a comprehensive review

Musculoskeletal disorders encompass a wide range of conditions that impact the bones, joints, muscles, and connective tissues within the body. Despite the ongoing debate on toxicity and administration, ozone demonstrated promise in managing several musculoskeletal disorders, modulating pain and inflammation. A literature search was conducted. The research design, methods, findings, and conclusions of the studies were then examined to evaluate the physiological effects, clinical application, controversies, and safety of the application of ozone in musculoskeletal medicine. Ozone application demonstrates considerable therapeutic applications in the management of musculoskeletal disorders, including fractures, osteoarthritis, and chronic pain syndromes. Despite these advantages, studies have raised concerns regarding its potential toxicity and emphasized the importance of adhering to stringent administration protocols to ensure safety. Additionally, heterogeneities in patient reactions and hazards from oxidizing agents were observed. Given its anti-inflammatory and analgesic qualities, ozone therapy holds potential in the management of several musculoskeletal disorders. Additional high-quality research with long follow-up is required to refine indications, efficacy and safety profile. Finally, for wider clinical acceptability and utilization, the development of international recommendations is essential.

Adrenomedullin has no effect on segmental bone defect healing but increases bone mineral density in rat model

OBJECTIVE

This study aimed to investigate the effect of adrenomedullin on the healing of the segmental bone defect in a rat model.

METHODS

Thirty-six Wistar rats were randomly divided into 6 groups based on follow-up periods and administered a dose of adrenomedullin hormone. In each group, bilaterally, a 2-mm bone defect was created at the diaphysis of the radius. Sodium chloride solution was administered to sham groups 3 times a week for 4 and 8 weeks intraperitoneally. Adrenomedullin was administered to the study groups 3 times a week: 15 μg-4 weeks, 15 μg-8 weeks, 30 μg-4 weeks, and 30 μg-8 weeks, respectively. After euthanasia, the segmental defects were evaluated by histomorphometric [new bone area (NBA)] and microtomographic [bone volume (BV), bone surface (BS), and bone mineral density (BMD)] analyses.

RESULTS

Although the 4- and 8-week 15 μg administered study groups had higher NBA values than the other study and control groups, the histomorphometric analysis did not reveal any statistical difference between the control and study groups regarding NBA (P > .05). In microtomographic analysis, BV was higher in the 15 μg 4-week group than 30 μg 4-week group (296.9 vs. 208.5, P=.003), and BS was lower in the 30 μg 4-week group than in the 4-week control group (695.5 vs. 1334.7, P=.005), but overall, no significant difference was found between the control and study groups (P > .05). Despite these minor differences in histomorphometric and microtomographic criteria indicating new bone formation, the BMD values of the 15 μg 8-week study group showed a significant increase compared with the control group (P=.001, respectively).

CONCLUSION

Adrenomedullin positively affected BMD at 15 μg, but this study could not show healing in the segmental defect site at different dose regimens. Further studies are needed to assess its effects on bone tissue trauma.

Development and characterization of a predictive microCT-based non-union model in Fischer F344 rats

INTRODUCTION

Non-unions remain a clinical problem and are characterised by the failure to heal after a defined period of time. Current preclinical non-union models apply a wide variety of techniques to diminish intrinsic healing potential deviating from the clinical situation. The aim of this study was to develop and characterise a non-union model in rats using internal plate fixation without the need for additional healing insults, whereby bone healing can be longitudinally assessed using microCT. It was hypothesized that healing/non-unions can be accurately predicted at early time points by microCT.

MATERIALS AND METHODS

Female, skeletally mature Fischer F344 rats received a 2 mm or 1 mm femoral osteotomy, stabilized with either a 2 mm thick plate or a 1.25 mm thick plate. Healing was monitored by microCT over 14 weeks and histological analysis at euthanasia. The mechanical environment was characterised using finite element (FE) modelling and biomechanical testing.

RESULTS

The majority of animals receiving the 2 mm thick plate displayed poor healing responses in both the 2 mm and 1 mm defect size groups. Bone and cartilage formation were markedly improved using the 1.25 mm thick plate. MicroCT could accurately predict bone forming capacity at early time points (3-4 weeks).

CONCLUSIONS

The 2 mm thick plating system confers poor healing responses in female Fischer F344 rats, comparable to atrophic non-unions. By reducing plate thickness to increase interfragmentary strain within the defect site healing is improved, leading to borderline healing situations or increased abundance of cartilage tissue present in the defect site with ultimate failure to bridge the defect (hypertrophic non-union). Furthermore, microCT can reliably identify delayed/non-healing animals within 4 weeks, thereby allowing their selective targeting for the testing of novel, clinically relevant treatment strategies in different clinical situations aimed at restoring impaired bone healing.

Three-Dimensional Printing for Craniofacial Bone Tissue Engineering

The basic concepts from the fields of biology and engineering are integrated into tissue engineering to develop constructs for the repair of damaged and/or absent tissues, respectively. The field has grown substantially over the past two decades, with particular interest in bone tissue engineering (BTE). Clinically, there are circumstances in which the quantity of bone that is necessary to restore form and function either exceeds the patient's healing capacity or bone's intrinsic regenerative capabilities. Vascularized osseous or osteocutaneous free flaps are the standard of care with autologous bone remaining the gold standard, but is commonly associated with donor site morbidity, graft resorption, increased operating time, and cost. Regardless of the size of a craniofacial defect, from trauma, pathology, and osteonecrosis, surgeons and engineers involved with reconstruction need to consider the complex three-dimensional (3D) geometry of the defect and its relationship to local structures. Three-dimensional printing has garnered significant attention and presents opportunities to use craniofacial BTE as a technology that offers a personalized approach to bony reconstruction. Clinicians and engineers are able to work together to produce patient-specific space-maintaining scaffolds tailored to site-specific defects, which are osteogenic, osseoconductive, osseoinductive, encourage angiogenesis/vasculogenesis, and mechanically stable upon implantation to prevent immediate failure. In this work, we review biological and engineering principles important in applying 3D printing technology to BTE for craniofacial reconstruction as well as present recent translational advancements in 3D printed bioactive ceramic scaffold technology.

Fracture union rates across a century of war: a systematic review of the literature

INTRODUCTION

Fractures have been a common denominator of the injury patterns observed over the past century of warfare. The fractures typified by the blast and ballistic injuries of war lead to high rates of bone loss, soft tissue injury and infection, greatly increasing the likelihood of non-union. Despite this, no reliable treatment strategy for non-union exists. This literature review aims to explore the rates of non-union across a century of conflict, in order to determine whether our ability to heal the fractures of war has improved.

METHODS

A systematic review of the literature was conducted, evaluating the rates of union in fractures sustained in a combat environment over a 100-year period. Only those fractures sustained through a ballistic or blast mechanism were included. The review was in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Quality and bias assessment was also undertaken.

RESULTS

Thirty studies met the inclusion criteria, with a total of 3232 fractures described across 15 different conflicts from the period 1919-2019. Male subjects made up 96% of cases, and tibial fractures predominated (39%). The lowest fracture union rate observed in a series was 50%. Linear regression analysis demonstrated that increasing years had no statistically significant impact on union rate.

CONCLUSIONS

Failure to improve fracture union rates is likely a result of numerous factors, including greater use of blast weaponry and better survivability of casualties. Finding novel strategies to promote fracture healing is a key defence research priority in order to improve the rates of fractures sustained in a combat environment.

Fracture Non-Union: A Review of Clinical Challenges and Future Research Needs

Non-union of bone following fracture is an orthopaedic condition with a high morbidity and clinical burden. Despite its estimated global prevalence of nine million annually, the limit of bone regeneration therapy still results in patients living with pain, a reduced quality of life and associated psychological, social and financial repercussions. This review provides an overview of the current epidemiological and aetiological data, and highlights where the clinical challenges in treating non-union lie. Current treatment strategies are discussed as well as promising future research foci. Development in biotechnologies to treat non-union provides exciting scope for more effective treatment for this debilitating condition.