[The influence of the number of bars on the axial compressive strength of uniplanar external fixators in polyurethane tibia models].
OBJECTIVE
This is an experimental study with the objective of analyses the increase of rigidity in synthetic tibia bones with external fixators, with single and double connecting rods and with stable and unstable fracture patterns.


METHODS
The external fixators were used in the monoplanar, half pin configuration submitted to an axial compression load using the connecting bar in different patterns. Forty-eight similar models to the human tibia had been used. In all the models were left an interval of 0,5 cm between the fragments and were made cuts of 15 masculine and 45 masculine to simulate stable and unstable fracture patterns, respectively. The models had been divided in four groups in accordance with the cut (15 masculine and 45 masculine) and the number of metallic bars in assembly (1 and 2 bars). The study used the Instron testing machine which the models were submitted to the axial load until the fragments that were separated by a gap made full contact.


RESULTS
The instability forces in the assembly with a double bar had been sufficiently superior to the forces with only one bar. It was still observed that the group with unstable fracture pattern and with only one connecting rod had a lesser variability compared with the other groups and presented more homogeneous results, with a minor average.


CONCLUSIONS
The assembly with a double longitudinal connecting rod in the studied models is more stable than the others to stand compression load.
Kume
Márcio Hiroaki
MH
Serviço de Ortopedia e Traumatologia, Hospital Sugisawa, Curitiba, PR, Brasil. ipem@evangelico.org.br
Malafaia
Osvaldo
O
Dietz
Ulrich Alexandre
UA
Deeke
Mark
M
Borsato
Karin Soldatelli
KS
Menegotto
Flavia Gonçalves
FG
Pundek
Marcia Regina Zanello
MR
D019245:Compressive Strength; D004867:Equipment Design; D016267:External Fixators; D008953:Models, Anatomic; D011140:Polyurethanes; D013977:Tibia; D013978:Tibial Fractures / Q000601:surgery*
D011140:Polyurethanes