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The effect of radial preload on the implant-bone interface: a cadaveric study
T L Biliouris1, E Schneider, B A Rahn
1M. E. Müller-Institute for Biomechanics, University of Bern, Switzerland.
Journal of Orthopaedic Trauma
|January 1, 1989
Summary
External fixation pin loosening is common. Applying radial preload with oversized pins can damage bone, potentially exceeding its elastic limit and causing structural damage. Further research is needed.
Area of Science:
- Orthopedic surgery
- Biomaterials engineering
- Skeletal biomechanics
Background:
- Pin loosening is a frequent complication in external fixation surgery.
- Preloading the implant-bone interface may prevent pin loosening.
- Radial preload offers multi-directional loading advantages.
Purpose of the Study:
- To examine how different radial preload levels affect the pin-bone interface.
- To evaluate microscopic bone damage resulting from varying degrees of preload.
Main Methods:
- 30 human cadaveric tibia segments were used.
- Custom oversized bolts were inserted into uniform drill holes.
- Histological analysis assessed bone microstructural damage.
Main Results:
- Misfits greater than 0.2 mm caused macroscopic fractures.
- Misfits exceeding 0.4 mm led to significant microscopic bone damage.
- High radial preload, beyond cortical bone's elastic limit, can occur with small misfits.
Conclusions:
- Oversized pins or screws may induce detrimental radial preload.
- This preload can cause significant structural damage to the surrounding bone.
- The clinical use of oversized implants in external fixation warrants caution.