A new animal model for delayed osseous union secondary to osteitis

Lars Helbig,Arash Moghaddam,Adriana Ivanova,Thorsten Guehring,Gerhard Schmidmaier,Kathrin Kaeppler,Christian Alexander Fischer,Svenja Rosenberger

doi:10.1186/s12891-015-0816-7

Abstract

BackgroundThe treatment of infection-related delayed bone unions is still very challenging for the orthopedic surgeon. The prevalence of such infection-related types of osteitis is high in complex fractures, particularly in open fractures with extensive soft-tissue damage. The aim of this study was to develop a new animal model for delayed union due to osteitis.MethodsAfter randomization to infected or non-infected groups 20 Sprague–Dawley rats underwent a transverse fracture of the midshaft tibia. After intramedullary inoculation with staphylococcus aureus (103 CFU) fracture stabilization was done by intramedullary titanium K-wires. After 5 weeks all rats were euthanized and underwent biomechanical testing to evaluate bone consolidation or delayed union, respectively. Micro-CT scans were additionally used to quantitatively evaluate the callus formation by the score of Lane and Sandhu. Blood samples were taken to analyze infectious disease markers (day 1, 14 and 35).ResultsBiomechanical testing showed a significant higher maximum torque in the non-infected group 5 weeks postoperatively compared with the infected group (p < 0.001). According to the Lane and Sandhu score a significantly higher callus formation was found in the non-infected group (p < 0.001). Similarly, the leucocyte count in the infected group was significantly higher than in the non-infected group (p < 0.05).ConclusionsHere we have established a new animal model for delayed osseous union secondary to osteitis. The animal model appears to be appropriate for future experimental studies to test new therapeutic strategies in these difficult to treat bone healing complications.

Highlights

The treatment of infection-related delayed bone unions is still very challenging for the orthopedic surgeon
In details the tibiae of the fractured non-infected group in the non-infected group (II) showed an average maximum torque of 0.081 +/− 0.078 Nm compared to 0.022 +/− 0.041 Nm in the fractured infected group I (Fig. 2)
Maximum torque (Nm) of the fractured side was significantly lower than the contralateral side in group I and II (p < 0.001, analysis of variance (ANOVA))

Summary

Introduction

The treatment of infection-related delayed bone unions is still very challenging for the orthopedic surgeon. The prevalence of such infection-related types of osteitis is high in complex fractures, in open fractures with extensive soft-tissue damage. The development of an effective treatment concept could result in a more confident treatment strategy and an overall improvement in patients’ quality of life. It would decrease the time and costs of treatment (e.g., a reduction in hospital stay, follow-up treatment, and resources). The goal of this study was to develop and establish a new animal model of delayed fracture healing in order to investigate innovative treatment concepts secondarily

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