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

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.