Development of an interlocked nail for segmental defects in the rabbit tibia

Area of Science:

• Orthopedic biomechanics
• Small animal surgical models
• Biomaterials and tissue engineering

Background:

• Previous animal models for tibial defects used large animals and non-locked implants.
• Existing rabbit tibia models lack the stability needed for evaluating bone regeneration technologies.
• Current human intramedullary nails increasingly utilize titanium alloy, unlike older stainless steel models.

Purpose of the Study:

• To develop and validate an interlocked titanium intramedullary nail for a rabbit tibial defect model.
• To establish a stable small animal model for studying new bone growth technologies.
• To compare the biomechanical stability of the novel interlocked nail against intact controls.

Main Methods:

• An interlocked titanium nail was designed and implanted in cadaver rabbit tibiae.
• Specimens underwent fatigue cycling simulating 12 weeks of animal gait (21,061 cycles) under combined compression and bending.
• Monotonic testing in compression and bending was performed before and after fatigue cycling.

Main Results:

• The novel interlocked nail provided fixation for the rabbit tibia defect model.
• Instrumented limbs showed significantly higher interfragmentary cyclic strain amplitudes (616 ± 139 µ-strain) compared to controls (136 ± 35 µ-strain).
• Monotonic strain amplitudes in the test limbs were substantially greater than controls, indicating load transfer similar to larger animal models.

Conclusions:

• The developed interlocked titanium nail provides a stable fixation method for rabbit tibial shaft fractures.
• This model offers a viable small animal platform for evaluating orthopedic innovations in bone defect healing.
• The biomechanical data support the use of this model for preclinical assessment of new bone regeneration strategies.