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Mechanical performance of pin clamps in external fixators
1Department of Orthopedics, Mayo Clinic/Mayo Foundation, Rochester, MN 55905.
Clinical Orthopaedics and Related Research
|November 1, 1989
Summary
External fixator clamp strength is crucial for stable bone fixation. This study found that specific pin configurations in Hoffmann and Orthofix clamps ensure adequate holding strength, preventing pin movement.
Area of Science:
- Orthopedic biomechanics
- Biomaterials engineering
- Surgical instrumentation
Background:
- Pin movement at the pin-bone interface can compromise external fixation rigidity.
- External fixators rely on clamp-pin interfaces for stable skeletal fixation.
- Variability in clamp holding strength can lead to suboptimal patient outcomes.
Purpose of the Study:
- To evaluate the pin holding strength of clamps in Hoffmann and Orthofix external fixator systems.
- To determine the torque resistance of pins within standard clamp configurations.
- To identify optimal pin configurations for maximizing clamp holding strength.
Main Methods:
- Torque resistance testing of pins within standard Hoffmann and Orthofix clamps.
- Evaluation of symmetric pin configurations (two-, three-, and four-pin setups).
- Analysis of pin torsional resistance across different configurations and clamp types.
Main Results:
- Hoffmann clamps showed satisfactory holding strength in symmetric two-, three-, and four-pin configurations.
- Orthofix clamps demonstrated higher holding strength in symmetric two- and three-pin configurations.
- High variation in torsional resistance was observed in other configurations, with some pins exhibiting low or no resistance.
Conclusions:
- External fixator clamp holding power is adequate only when specific application guidelines are followed.
- Instrumented torque wrenches can assess and ensure uniform pin-fastening strength.
- Adherence to proper application techniques is critical for achieving reliable fixation rigidity.