Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_

Poster
Topic: General Orthopaedics
Abstract number: 26194
HEXAPOD EXTERNAL FIXATOR FOR MOTORIZED DEFORMITY CORRECTION
Robert WENDLANDT 1 , Klaus SEIDE 2 , Arndt-Peter SCHULZ 1 , Christian JUERGENS 1
1 University Hospital Schleswig-Holstein, Luebeck (GERMANY),
2 Berufsgenossenschaftliches Unfallkrankenhaus Hamburg, Hamburg (GERMANY)
Introduction: External fixation is a commonly used technique for fracture fixation as
well as for correction of deformities. Systems with six degree of freedom kinematics
like the hexapod external fixator are especially suited for complex maneuvers in
several directions and rotations simultaneously. Materials and Methods: Based upon
the manual hexapod external fixator well established in clinical routine the system
was developed by replacing the manual actuators with motor-driven actuators. A
motor-unit containing a DC motor and gearhead in a watertight housing is attached to
telescopic rods. The actuators are connected to a control unit containing power
supply, motor-drive electronics and a Bluetooth transceiver which is connected
wirelessly to a laptop running the control software. The system was first tested for
speed, force and accuracy. Then it was applied clinically for correcting a deformity.
Results: The speed of the actuators is 2.5mm/s. The actuation force of the system is
483N. Accuracy of the complete system was better than 1mm and 1°. The clinical
application of the system for the correction of a angle of 3.5° in varus and 13.3°
posterior deformity determined by two x-ray images taken from frontal and lateral
reduced the varus deformity completely while 6° of posterior deformity remained.
Discussion: Speed and force of the robotic hexapod external fixator are sufficient in
comparison with literature which was clearly seen also in the clinical correction.
Fluoroscopy pictures taken during the correction allowed only a limited field of view
therefore the deformity was not corrected completely.
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