Measurement of fracture gap motion in external fixation
The Journal of Trauma
|September 1, 1981
Summary
A new machine measures fracture gap motion ex vivo. External fixators showed more shear displacement than medullary nails, with double frames improving stability.
Area of Science:
- Orthopedic biomechanics
- Biomaterials science
Background:
- Fracture fixation devices aim to stabilize bone segments, promoting healing.
- Understanding in vivo mechanical behavior of fixation devices is crucial for clinical success.
Purpose of the Study:
- To develop and utilize an ex vivo testing apparatus for quantifying fracture gap motion.
- To compare the mechanical stability of Hoffmann external fixators (single and double frame) against a Küntscher medullary nail.
Main Methods:
- Devised a testing machine for direct measurement of bending and shear at fracture sites.
- Applied various loading conditions to assess device performance.
- Quantified shear displacements and hinge motion for each fixation type.
Main Results:
- External fixators exhibited greater shear displacements (0.4-1.7 mm) compared to medullary nails (0.3 mm).
- Transitioning from single to double frame Hoffmann fixators reduced hinge motion by 50% and shear by 25%.
Conclusions:
- The developed apparatus effectively measures fracture gap motion under load.
- Medullary nails offer greater inherent stability against shear forces compared to external fixators.
- Double frame configurations significantly enhance the stability of external fixation systems.
