A new device to control mechanical environment in bone defect healing in rats

Area of Science:

• Orthopedics
• Biomaterials Science
• Regenerative Medicine

Background:

• Mechanical forces critically impact bone healing processes.
• Existing small animal models lack precise control over the mechanical environment.
• A need exists for reliable models to study bone regeneration under defined mechanical conditions.

Purpose of the Study:

• To develop and validate a novel small animal model for controlled mechanical stimulation in bone healing.
• To assess the influence of implant material (steel vs. titanium) and fixator offset on mechanical properties.
• To evaluate the in vivo performance and complication rates of the developed model.

Main Methods:

• Design and in vitro testing of an external fixator for rat femurs with adjustable offset and Kirschner wires (titanium or steel).
• In vitro mechanical testing of axial and torsional stiffness across different offsets and materials.
• In vivo evaluation in Sprague-Dawley rats over 6 weeks, monitoring well-being, complications, and bone healing.

Main Results:

• Steel fixators demonstrated higher torsional and axial stiffness than titanium.
• Increasing the fixator offset from 7.5 mm to 15 mm significantly decreased stiffness.
• No significant difference in complication rates was observed between groups, with an overall rate of 5.2%.

Conclusions:

• A reproducible small animal model for bone defect healing with controlled mechanical conditions was successfully established.
• The model allows for defined manipulation of mechanical stimuli at the bone defect site.
• This model provides a valuable tool for investigating the mechanobiology of bone regeneration.