Pull-Out Strength of 0°/30° Kirschner Wire Syringe External Fixators With and Without Polymer Augmentation: A Biomechanical Study
Pichitchai Atthakomol MD*, Noppadol Wangjiraphan MD*, Supachard Krudtong MS**, Jirasak Panya MS**, Sirichai Leuvitoonvejchakij MD*, Jirachart Kraisarin MD*, Kanit Sananpanich MD*
Affiliation : * Department of Orthopaedics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand ** Department of Mechanical Engineering, Faculty of Engineering, Rajamangala University of Technology Lanna Chiang Mai, Chiang Mai, Thailand
Background : Hand external fixators are in use worldwide and insulin syringes can generally be found in an operating room.
Objective : To compare the pull-out strength between degrees of Kirschner wire fixation (0° and 30°) and the effect of filling
an insulin syringe with polymer.
Material and Method: Pull-out strength was compared between a syringe external fixator and a bone or plastic tube model.
Fifty-two plastic tube models and 20 dry phalangeal bones were included. The syringe external fixator was attached via
two Kirschner wires. Four variations were studied: 0° non-polymer, 0° with polymer augmentation, 30° non-polymer, and
30° with polymer augmentation. The pull-out strength was measured in each group.
Results : The strength of polymer augmentation was higher than non-polymer augmentation at 0° (p = 0.0003) and 30°
(p = 0.0002). The Kirschner wire at 30° provided more pull-out strength than at 0° (p = 0.0003) using the syringe with no
polymer. However, using the syringe with polymer augmentation, there was no significant difference (p = 0.5136).
Conclusion : Polymer augmentation significantly increases the pull-out strength at both degrees of fixation. The degree
of fixation significantly increases the pull-out strength only in the non-polymer group, where pinning at 30° was superior
to 0°.
Keywords : Biomechanical, Syringe external fixator, Pull-out strength, Degree of fixation, Polymer
