Related Experiment Videos
Assessment of external fixator reusability using load- and cycle-dependent tests
Maiko Matsuura1, Smain Lounici, Nozomu Inoue
1Orthopaedic Biomechanics Laboratory, School of Medicine, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205-2196, USA.
Clinical Orthopaedics and Related Research
|February 13, 2003
Summary
Establishing a fatigue testing method for external fixator reuse is crucial. High-load testing revealed critical failure points, while low-load testing indicated component wear after simulated clinical uses.
Area of Science:
- Orthopedic biomechanics
- Medical device engineering
- Materials science
Background:
- No standardized fatigue testing method exists for external fixator frame reuse.
- Assessing the durability and safety of reusable external fixators is essential for clinical practice.
Purpose of the Study:
- To establish and validate a fatigue testing protocol for evaluating the reusability of external fixator systems.
- To identify critical components and failure modes associated with repeated use of external fixators.
Main Methods:
- Testing of a unilateral DynaFix external fixator system under high-load, low-cycle (900-150 N at 5 Hz) and low-load, high-cycle (450-100 N at 10 Hz) conditions.
- Simulating single clinical use with 500,000 and 1 million cycles, respectively, to meet Food and Drug Administration requirements.
Main Results:
- High-load, low-cycle testing resulted in substantial serrated joint failure before completing one simulated use.
- Low-load, high-cycle testing allowed completion of three simulated uses, but 25% of serrated joint components developed hairline cracks.
- Wear and deformation were observed in rotary joint set screws and telescoping mechanisms under low-load, high-cycle conditions.
Conclusions:
- The high-load, low-cycle test effectively identifies components requiring examination and replacement for fixator reuse.
- Reusability of unilateral DynaFix external fixators should be limited due to cumulative fatigue damage observed under increased loading cycles.
- Further investigation into wear and deformation is necessary to establish safe reuse protocols for external fixators.