Fracture Apparatus Design and Protocol Optimization for Closed-stabilized Fractures in Rodents

Summary

The goal of the protocol is to optimize the fracture generation parameters to yield consistent fractures. This protocol accounts for the variations in bone size and morphology that may exist between animals. Additionally, a cost-effective, adjustable fracture apparatus is described.

Abstract

The reliable generation of consistent stabilized fractures in animal models is essential for understanding the biology of bone regeneration and developing therapeutics and devices. However, available injury models are plagued by inconsistency resulting in wasted animals and resources and imperfect data. To address this problem of fracture heterogeneity, the purpose of the method described herein is to optimize fracture generation parameters specific to each animal and yield a consistent fracture location and pattern. This protocol accounts for variations in bone size and morphology that may exist between mouse strains and can be adapted to generate consistent fractures in other species, such as rat. Additionally, a cost-effective, adjustable fracture apparatus is described. Compared to current stabilized fracture techniques, the optimization protocol and new fracture apparatus demonstrate increased consistency in stabilized fracture patterns and locations. Using optimized parameters specific to the sample type, the described protocol increases the precision of induced traumas, minimizing the fracture heterogeneity typically observed in closed-fracture generation procedures.

Introduction

Research on fracture healing is necessary to address a large clinical and economic problem. Each year over 12 million fractures are treated in the United States¹, costing $80 billion per year². The likelihood of a male or female suffering a fracture in their lifetime is 25% and 44%, respectively³. Problems associated with fracture healing are expected to increase with increased comorbidities as the population ages. To study and address this problem, robust models of fracture generation and stabilization are required. Rodent models are ideally suited for this purpose. They provide clinical relevanc....

Protocol

This protocol was developed to ensure that animals are not used needlessly and are spared all unnecessary pain and distress; it adheres to all applicable federal, state, local, and institutional laws and guidelines governing animal research. The protocol was developed under the guidance of a university-wide Laboratory Animal Medicine Program directed by veterinarians specialized in laboratory animal medicine. The protocol was reviewed and approved by the Institutional Animal Care and Use Committee (IACUC).

1. Fracture Tower Construction

Note: All parts are listed in the materials section (Table of Materials....

Results

The guillotine previously used in our laboratory was developed in 2004 and was based on models published by Einhorn²¹. The design did not permit adjustments to adequately account for any differences in bone morphology and did not permit a reproducible positioning of the limb. Furthermore, the previous apparatus required two people to operate it. Therefore, we designed, engineered, and built a new fracture apparatus. The main design goal was the possibility to the h.......

Discussion

This fracture optimization and generation protocol provides researchers with an efficient method to derive at fracture parameters and perform a minimally invasive procedure, which produces precise, repeatable, transverse fractures. Additionally, this protocol establishes a common set of fracture generation parameters, which promotes method consistency amongst researchers. These parameters will enable the creation of a common fracture database to establish fracture standards based on a variety of parameters (e.g........

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Support Subassembly			Supplementary Figure 1
Beam, Support--Jaw Section	80/20	1003 x 9.00	w/ #7042 at A, C, in Left End
Beam, Support--Horizontal Section	80/20	1002 x 14.00
Beam, Support--Vertical 1	80/20	1050 x 10.50	w/ #7042 at A in Left End and at A in Right End
Beam, Support--Vertical 2	80/20	1010 x 10.50	w/ #7042 at D, B in Left End and at A in Right End
Beam, Support--Plate Mount	80/20	1030 x 8.00	w/ #7036 at Left End
Beam, Support--Magnet	80/20	1010 x 13.50	w/ #7042 at A, C, in Right End
Anchors (3)	80/20	3392
Double Anchor (3)	80/20	3091
Bolt Assembly (6)	80/20	3386	1/4-20 x 3/8"
Button Head Socket Cap Screw (6)	80/20	3604	1/4-20 x 3/4"
Ram Subassembly			Supplementary Figure 2
Block, Stop	Custom		Supplementary Figure 3
Block, Guide	Custom		Supplementary Figure 3
Rod, Ram	Custom		Supplementary Figure 4
Alignment Screw	Custom		Supplementary Figure 5
Plate, Mounting	Custom		Supplementary Figure 6
Linear Sleeve Bearing (2)	McMaster-Carr	8649T2
Hex Nut (3)	McMaster-Carr	92673A125	3/8-16 UNC
Socket Cap Screw (8)	McMaster-Carr	92196A108	4/40 x 3/8"
Socket Cap Screw (6)	McMaster-Carr	92196A032	4/40 x 1 1/8"
Socket Cap Screw (1)	McMaster-Carr	92196A267	10/32 3/8"
Magnet Subassembly			Supplementary Figure 7
Mount, Magnet	Custom		Supplementary Figure 8
Power Supply	McMaster-Carr	70235K23
Foot Switch	McMaster-Carr	7376k2
Electromagnet	McMaster-Carr	5698k111
Wire - 10 feet	McMaster-Carr	9936k12
Rod, Magnet	McMaster-Carr	95412A566	1/4" Threaded Rod x 7"
Corner Bracket (6)	80/20	4108
Socket Cap Screw (1)	McMaster-Carr	92196A705	10/32 1 1/4"
Hex Nut (4)	McMaster-Carr	92673A113	1/4-20 UNC
Complete Assembly			Supplementary Figure 9
Bracket, Leg Jaw (2)	Custom		Supplementary Figure 10
Platform, Fracture	Custom		Supplementary Figure 11
Jig, Positioning-Fracture	Custom		Supplementary Figure 12
Other
Pin Cutter	Medical Supplies and Equipment	150S
Needles	Sigma	Z192430, Z192376	23g x 1.5" - mouse femur, 27g x 1.25" - mouse tibia