Femoral forces during limb lengthening in children

Area of Science:

• Orthopedics
• Biomechanical Engineering
• Regenerative Medicine

Background:

• Femoral lengthening is a critical orthopedic procedure for limb reconstruction.
• Understanding the biomechanical forces during distraction osteogenesis is essential for optimizing treatment outcomes.
• The Ilizarov frame is a common external fixation device used in limb lengthening.

Purpose of the Study:

• To quantify the axial and bending forces experienced by the Ilizarov femoral frame during distraction osteogenesis.
• To investigate the diurnal variation of these forces.
• To compare femoral distraction forces with previously reported tibial distraction forces.

Main Methods:

• A custom system with force transducers integrated into an Ilizarov femoral frame was developed.
• Measurements were collected from three adolescent subjects during overnight and weight-bearing conditions.
• Axial force and bending moments were analyzed before and after lengthening procedures.

Main Results:

• A progressive increase in axial load was observed during distraction, with peak forces ranging from 428 N to 673 N.
• Minimal changes in frame forces occurred during weight-bearing.
• A significant diurnal variation in axial load was detected (p < 0.01), with forces at midnight being 113 N higher than in the morning.
• Femoral distraction forces were found to be greater than those previously reported for tibial distraction.

Conclusions:

• Femoral distraction generates significant axial forces, exceeding those in the tibia.
• Diurnal variations in axial load are present during femoral lengthening.
• The stiff bone callus may be the source of these generated forces, highlighting the dynamic nature of bone regeneration.