Changes in canine peripheral nerves during experimental callus distraction

Area of Science:

• Orthopedics
• Regenerative Medicine
• Neuroscience

Background:

• Leg lengthening procedures, such as callus distraction, are crucial in orthopedic surgery.
• Understanding the impact of these procedures on peripheral nerves is essential for patient outcomes.

Purpose of the Study:

• To investigate the effects of tibial lengthening via callus distraction on the tibial and peroneal nerves in beagles.
• To analyze nerve fiber alterations, including degeneration and regeneration, following the distraction osteogenesis process.

Main Methods:

• Tibial lengthening was performed on beagles using a ring fixator and callus distraction technique.
• Nerves were harvested at different time points (immediately after distraction and after consolidation) for morphometric and electron microscopic analysis.
• A control group with tibial osteotomy and external fixation without distraction was included for comparison.

Main Results:

• Minor alterations in myelinated nerve fibers were observed, including remyelination and single axon degeneration.
• Electron microscopy revealed late Wallerian degeneration and axonal regeneration in nonmyelinated axons.
• Morphometric analysis showed increased fiber density and reduced axon/fiber diameter during consolidation, with tibial nerve changes resolving post-consolidation.

Conclusions:

• Callus distraction induces moderate, transient degenerative changes in peripheral nerves.
• The nerves exhibit repair mechanisms, leading to near-complete recovery and some evidence of nerve fiber growth.
• These findings support the safety and regenerative potential of callus distraction in limb lengthening procedures.