gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2015)

20.10. - 23.10.2015, Berlin

Biomechanical investigation and clinical application of new external fixation system

Meeting Abstract

  • presenting/speaker Milorad Mitkovic - University Clinic for Orthopaedic and traumatology, Nis, Serbia
  • Sasa Milenkovic - University Clinic for Orthopaedic and traumatology, Nis, Serbia
  • Ivan Micic - University Clinic for Orthopaedic and traumatology, Nis, Serbia
  • Milan Mitkovic - University Clinic for Orthopaedic and traumatology, Nis, Serbia

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2015). Berlin, 20.-23.10.2015. Düsseldorf: German Medical Science GMS Publishing House; 2015. DocPO30-788

doi: 10.3205/15dkou833, urn:nbn:de:0183-15dkou8337

Veröffentlicht: 5. Oktober 2015

© 2015 Mitkovic et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe http://creativecommons.org/licenses/by/4.0/.


Gliederung

Text

Objectives: External fixation using pins has usually been referred to as two-dimensional (2D) systems where all pins constituting one cluster of pins are in a single plane. If pins are parallel, as in most conventional external fixation devices, than antero-posterior (AP) and lateral (LL) stability are not balanced. Such a system is very stable in the plane of the pins but unstable in the perpendicular plane. The bending stiffness of human long bones has a balanced AP:LL ratio. A new external fixation system has similar biomechanics as human long bones have. The goal of this study is biomechanical testing and clinical application of new external fixator which biomechanical features are similar to biomechanical features of natural long bones.

Methods: Original 3D unilateral external fixation system has widely been investigated biomechanically in AO institute in Davos (Switzerland). This external fixation system consists of three components only providing extremely simple application and dynamic fixation of bones and different joints. This simple external fixator functions as an accurate reduction device at the same time, minimizing need for fluoroscopy. Each of three component can be connected to other two component on different ways providing so chess-like possibilities for building of different frame. Comparative investigation of two type of frames have been performed: 1. external fixator with parallel pins (2D system) and 2. original external fixator with 90 degrees convergent pins (3D system). Clinically this system has been statistically analyzed to series of 597 patients.

Results: Biomechanical testing of external fixator with parallel pins (2D) has shown non-balanced AP:lateral stability, whereas AP displacement during 4-point bending test was 2.499 mm at 250 N force; and lateral displacement during 4-point bending test was 0.912 mm at 250 N force. The ratio was AP:lateral=1:2.74. Axial displacement was 2.932 mm under the axial loading of 200 N. Maximal torque during the loading of 10 Nm was 10.122 degrees. Original external fixator with 90-degree convergent orientation of the pins (3D) has shown balanced AP:lateral stability; whereas AP displacement during 4-point bending test was 1.901 mm at 250 N force; and lateral displacement during 4-point bending test was 2.108 mm at 250 N force. The ratio was AP:lateral=1.1:1. Axial displacement was 1.801 mm under the axial loading of 200 N. Maximal torque during the loading of 10 Nm was 10.382 degrees. Torque stability was similar in all frames. Application of original (3D) external fixation device in the treatment of open and closed fractures as definitive method in the series of 597 patients has been shown that overall success of fracture healing was 96.8%. Original (3D) system has been proven as suitable tool for closed fracture reduction. This feature can be used during the internal fixation (plate or intramedulary nail).

Conclusion: Our study suggests that the use of this 3D unilateral system is suitable for routine use.