Masquelet induced membrane technique for treatment of rat chronic osteomyelitis

Choosing the right animal model for osteomyelitis research: Considerations and challenges

Osteomyelitis is a debilitating bone disorder characterized by an inflammatory process involving the bone marrow, bone cortex, periosteum, and surrounding soft tissue, which can ultimately result in bone destruction. The etiology of osteomyelitis can be infectious, caused by various microorganisms, or noninfectious, such as chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO). Researchers have turned to animal models to study the pathophysiology of osteomyelitis. However, selecting an appropriate animal model that accurately recapitulates the human pathology of osteomyelitis while controlling for multiple variables that influence different clinical presentations remains a significant challenge. In this review, we present an overview of various animal models used in osteomyelitis research, including rodent, rabbit, avian/chicken, porcine, minipig, canine, sheep, and goat models. We discuss the characteristics of each animal model and the corresponding clinical scenarios that can provide a basic rationale for experimental selection. This review highlights the importance of selecting an appropriate animal model for osteomyelitis research to improve the accuracy of the results and facilitate the development of novel treatment and management strategies.

Role of Animal Models to Advance Research of Bacterial Osteomyelitis

Osteomyelitis is an inflammatory bone disease typically caused by infectious microorganisms, often bacteria, which causes progressive bone destruction and loss. The most common bacteria associated with chronic osteomyelitis is Staphylococcus aureus. The incidence of osteomyelitis in the United States is estimated to be upwards of 50,000 cases annually and places a significant burden upon the healthcare system. There are three general categories of osteomyelitis: hematogenous; secondary to spread from a contiguous focus of infection, often from trauma or implanted medical devices and materials; and secondary to vascular disease, often a result of diabetic foot ulcers. Independent of the route of infection, osteomyelitis is often challenging to diagnose and treat, and the effect on the patient's quality of life is significant. Therapy for osteomyelitis varies based on category and clinical variables in each case. Therapeutic strategies are typically reliant upon protracted antimicrobial therapy and surgical interventions. Therapy is most successful when intensive and initiated early, although infection may recur months to years later. Also, treatment is accompanied by risks such as systemic toxicity, selection for antimicrobial drug resistance from prolonged antimicrobial use, and loss of form or function of the affected area due to radical surgical debridement or implant removal. The challenges of diagnosis and successful treatment, as well as the negative impacts on patient's quality of life, exemplify the need for improved strategies to combat bacterial osteomyelitis. There are many in vitro and in vivo investigations aimed toward better understanding of the pathophysiology of bacterial osteomyelitis, as well as improved diagnostic and therapeutic strategies. Here, we review the role of animal models utilized for the study of bacterial osteomyelitis and their critically important role in understanding and improving the management of bacterial osteomyelitis.

One-stage debridement and bone transport versus first-stage debridement and second-stage bone transport for the management of lower limb post-traumatic osteomyelitis

Background

Treatment of lower limb post-traumatic osteomyelitis used to be a staged process, with radical debridement of bone and soft tissues at first stage, followed by a second-stage limb reconstruction operation to restore the limb integrity. Some studies recently reported that achieving infection eradication and limb reconstruction at single-stage seems to be an effective method for lower limb infection, but a comparative study remains lacking. This study aims to compare the results of radical debridement combined with a first/second-staged osteotomy and bone transport, for the management of lower limb post-traumatic osteomyelitis.

Methods

From January 2013 to June 2018, a total of 102 patients with lower limb post-traumatic osteomyelitis met the criteria were included for analysis, in which 70 patients received one-stage debridement, antibiotic-loaded implantation, metaphysis osteotomy and bone transport were named as one-stage group, while 32 patients with first-stage debridement and antibiotic-loaded calcium sulfate implantation, second-stage osteotomy and bone transport were devised as two-stage group. The outcomes of hospitalization (hospital stay, costs of treatment, surgical time, antibiotic usage) and follow-up (infection-free, treatment failure, infection recurrence, external fixation index (EFI) and docking site union) between the two groups were retrospectively compared.

Results

For outcomes of hospitalization, patients in the one-stage group had batter results on hospital stay (18.2 days versus 28.9 days, P ​< ​0.05), surgical time (164.8 ​min versus 257.4 ​min, P ​< ​0.05), cost of treatment (¥101726.1 versus ¥126718.8, P ​< ​0.05) and the course of antibiotic usage (10.3 days versus 12.0 days, P ​< ​0.05). During the follow-up, 87.1% (61/70) patients in the one-stage group compared to 93.8% (30/32) patients in the two-stage group achieved infection-free (P ​> ​0.05) without any additional debridement operation. 94.3% (66/70) patients in the one-stage group earned wound healing after the operation, comparing to 96.9% (31/32) patients healed in the two-stage group (P ​> ​0.05). Uncontrolled infection was observed on 4 (5.7%) patients in the one-stage group and 1 (3.1%) patients in the two-stage group (P ​> ​0.05), with a result of three achieved infection free in the one-stage group and one patient suffered from amputation in each group respectively. 5 (7.2%) patients in the one-stage group and 1 (3.2%) patient in the two-stage group encountered with infection recurrence (P ​> ​0.05) and were well-managed with re-debridement and antibiotics usage. Significance was not found between two groups on EFI (74.8 days/cm versus 69.0 days/cm, P ​> ​0.05) and docking site nonunion rate (14.5% versus 18.9%, P ​> ​0.05), indicating that bone transport in different stages played a less essential role on bone generation process. The other complications, such as prolonged aseptic drainage [24.3% (17/70) versus 21.9% (7/32)], re-fracture [5.8% (4/69) versus 3.2% (1/31)], pin-tract infection [23.2% (16/69) versus 19.4% (6/31)], joint stiffness and deformity [26.1% (18/69) versus 32.3% (10/31)], also showed less significance when comparing between two groups (P ​> ​0.05), suggesting that different transport stages play little role on complications formation.

Conclusions

One-stage radical debridement and bone transport was proven to be a safe and effective method for treating static (or near static) lower limb osteomyelitis.

Translational potential statement

Translational potential statement One-stage debridement and bone transport is sample, effective and time-saving, with similar complications compared to conventional two-stage protocol. This treatment protocol might provide an alternative for the treatment of static (or near static) lower limb osteomyelitis.

A systematic review on current osteosynthesis-associated infection animal fracture models

Objective

Osteosynthesis-associated infection is a challenging complication post fracture fixation, burdening the patients and the orthopaedic surgeons alike. A clinically relevant animal model is critical in devising new therapeutic strategies. Our aim was to perform a systematic review to evaluate existing preclinical models and identify their applications in aspects of animal selection, bacterial induction, fracture fixation and complications.

Methods

A systematic literature research was conducted in PubMed and Embase up to February 2020. A total of 31 studies were included. Information on the animal, bacterial induction, fracture fixation, healing result and complications were extracted.

Results

Animals selected included murine (23), rabbit (6), ewe (1) and goat (1). Larger animals had enabled the use of human-sized implant, however small animals were more economical and easier in handling. Staphylococcus aureus (S. aureus) was the most frequently chosen bacteria for induction. Bacterial inoculation dose ranged from 10^2-8 ​CFU. Consistent and replicable infections were observed from 10⁴ ​CFU in general. Methods of inoculation included injections of bacterial suspension (20), placement of foreign objects (8) and pretreatment of implants with established biofilm (3). Intramedullary implants (13), plates and screws (18) were used in most models. Radiological (29) and histological evaluations (24) in osseous healing were performed. Complications such as instability of fracture fixation (7), unexpected surgical death (5), sepsis (1) and persistent lameness (1) were encountered.

Conclusion

The most common animal model is the S. aureus infected open fracture internally fixated. Replicable infections were mainly from 10⁴ ​CFU of bacteria. However, with the increase in antibiotic resistance, future directions should explore polymicrobial and antibiotic resistant strains, as these will no doubt play a major role in bone infection. Currently, there is also a lack of osteoporotic bone infection models and the pathophysiology is unexplored, which would be important with our aging population.

The translational potential of this article

This systematic review provides an updated overview and compares the currently available animal models of osteosynthesis-associated infections. A discussion on future research directions and suggestion of animal model settings were made, which is expected to advance the research in this field.