Comparison of the mechanical performance of three types of unilateral, dynamizable external fixators

Abstract

Due to the increasing popularity of unilateral dynamizable external fixators for treating tibial shaft fractures, many new devices are being introduced onto the market. Especially in such half-frame fixators, the choice of any particular device depends above all on the stability of its construction. This study compares the biomechanical stability of three systems tested in axial compression, torsion, and both anterior-posterior and medial-lateral bending. In terms of the nondynamized phase, the AO/ASIF tubular fixator (as a one-plane, double-tube, unilateral frame) and the Martin Mono-Dynafix are, in general, less stable than the Orthofix fixator. After dynamization, the AO/ASIF system becomes particularly weak and offers low resistance especially to torque and any force that is perpendicular to the plane of assembly. The other two tested devices evinced much more stability; the Orthofix fixator seems superior to the Dynafix due to the different diameter of its screws.

Distal tibial metaphyseal fractures: the role of fibular fixation

“…These properties are important in achieving sufficient control for early weightbearing and preventing late malalignment. In the study by Jaskulka et al the Orthofix monolateral fixator retained the highest mechanical stability after dynamisation as compared with the Marin Monodynafix and AO tubular fixators (in a single-plane, double-tube, unilateral configuration) [77]. Furthermore, the ability to reduce fracture gaps by adjusting the telescopic body (Fig.…”

Rigidity of unilateral external fixators—A biomechanical study

“…In a previous study Jaskulka et al showed more rigidity of the ProCallus Fixator ® upon loading in parallel, transverse, and axial (i.e., compression) direction; however, they could not confirm that this was due to differences in rigidity of the devices or due to the difference in diameter of the screws [6]. Since the pin numbers, pin diameter, pin material and pin offset distance are considered as important determinants of fixation stiffness [2,7], these factors were kept constant in the present study.…”

Correlation of Shear to Compression for Progressive Fracture Obliquity

“…Thus, from the interfragmentary strain theory bore the concept of cyclical loading. Many authors advocate mild early loading to promote strain stimuli at 3 to 6 weeks [8,10,13]. The mild axial pistoning, with diminution in the bending moment arm, is what creates a suitable healing environment with the Ilizarov fixator.…”