Less-Invasive Technique for Non-stabilized Mandibular Fracture in Mouse Models

Summary

This protocol presents a comprehensive and efficient method for analyzing mandibular bone repair. We describe a reproducible technique for non-stabilized mandibular fracture in a mouse model, allowing analysis of the process of endochondral bone repair with minimal tissue damage and bone loss.

Abstract

Non-stabilized fractures can be made at mandibular sites in mice, thus making it possible to analyze bone repair using an endochondral ossification mode. To most accurately reflect this process in vivo, it is necessary to have a standardized protocol to avoid excessive bone loss and soft tissue damage, particularly at the mandibular site, an anatomical site characterized by minimal access. To our knowledge, we describe for the first time a less-invasive protocol of non-stabilized mandibular fracture in mice. Adult mice are anesthetized with isoflurane and receive a preoperative dose of buprenorphine by subcutaneous injection. A submandibular approach is performed, with a skin incision made along the inferior border of the mandible. The masseter muscle is elevated in a subperiosteal plane along the mandibular ramus with a periosteal elevator. A vertical and complete fracture of the ramus is performed from the basilar border to the coronoid notch (between condylar and coronoid processes), using a piezoelectric bone surgery device under saline serum irrigation at the basilar edge and scissors to complete the fracture of the mandibular ramus. The skin approach is closed by silk sutures. This detailed procedure for non-stabilized mandibular fractures offers an efficient procedure allowing minimal bone loss and soft tissue damage. This technique ensures successful and consistent results to accurately reflect the process of endochondral bone repair in mouse models.

Introduction

Bone repair implies both membranous and endochondral ossification processes, depending on the fracture or osteotomy stabilization. Bone repair following stabilized bone osteotomies or fractures relies on membranous ossification, whereas non-stabilized fractures or poorly stabilized osteotomies consolidate according to a mode of endochondral ossification¹. Membranous bone repair is characterized by bone formation by direct differentiation of mesenchymal cells into osteoblasts, whereas endochondral bone repair involves the formation of a transient cartilaginous template, which differentiates into osteoblasts to form the bone callus

Protocol

This protocol follows the animal care guidelines of Imagine Institute and has been validated by ethical committees and the French ministry (APAFIS 26995).

1. Animals

1. Determine the number of animals per group. We recommend 12 animals per group. Determine the sex and age of mice. This protocol is adapted for 6-week-old C57BL/6J mice (male or female).
2. Give animals, at least 1 week before the procedure, nutritional supplement gel for acclimation.

2. Surgical procedure

1. Prepare the material required. Autoclave the instruments: scissors, needle d....

Results

As for in vivo surgical procedures, to optimally perform this procedure of non-stabilized mandibular fracture in a mouse model, specific learning and training are required.

This technique for non-stabilized mandibular fracture allows the study of the endochondral bone repair process. Following euthanasia, mandibular samples were collected in 4% paraformaldehyde (24 h). After full decalcification with EDTA pH 8, sections were embedded in paraffin. Sagittal serial sections were performe.......

Discussion

The technique allows the realization of non-stabilized mandibular fractures in a mouse model within a minimal open approach in a short procedure time (around 10 min or less). This short-time procedure limits the risk of animal morbidity and death, especially in small animals such as mice. To obtain comparable results in the analysis of the endochondral bone repair process, particular care should be taken to perform the mandibular fractures in the same direction without abnormal split of the mandibular angle, as this unde.......

Materials

Name	Company	Catalog Number	Comments
Buprenorphine : Buprecare 0.3 mg/kg	Animalcare
Elevator OBWEGESER width 6mm Length 17,5cm	Collin Medical	HA 5905
Forceps : Pad Plate MORIA 11 cm N°5	MORIA	9906
Heating table Bioseblab 55 cm x 33 cm	Bioseblab	707
Needle HOLDER : Micro Halsey Needle Holder - Metal	LABODERM	21,100
Neo Clear	Merck Millipore, Darmstadt, Germany	109843
Ocry Gel Tube 10 g (eye lubricant)	tvm lab	3.70045E+12
Piezotome 2 ASS FINAL	ACTEON	X57402
Piezotome insert Piezocision PZ3	ACTEON	F87574
Scissors micro	MORIA	MC52
Silk sutures PERMA HAND SEIDE  / MERSILK	ETHICON	REF 18501G
Straight scissors	MORIA	4877A
Vetflurane (isoflurane) 250 ml	VIRBAC	VET066 (Centravet)