Biomechanics of external fixation of distal tibial extra-articular fractures: is spanning the ankle with a foot plate desirable?
OBJECTIVE
To compare the mechanical stability of external fixation with and without spanning of the ankle joint with a foot plate in an in vitro model of extra-articular distal tibia fractures.


METHODS
A laboratory investigation was performed to evaluate the mechanical behavior of external fixation of extra-articular distal tibia fractures using a fixator with and without a foot plate. Ten fresh-frozen lower extremities (5 pairs) with a simulated OTA 43-A3.3 fracture were stabilized with an Ilizarov hybrid fixator with and without a foot plate.


METHODS
All mechanical testing was performed with a servohydraulic test frame (MTS Bionix 858, Minneapolis, MN).


METHODS
Deformation characteristics as a function of load were compared for an Ilizarov fixator with and without a foot plate under identical conditions of forefoot loading from 0 to 100 N. Relative interfragmentary motions (vertical and horizontal translations and rotation) were measured.


RESULTS
There was significantly more vertical translation (2.57 +/- 0.97 mm vs. -0.83 +/- 0.64 mm) and angular displacement (4.49 +/- 0.45 degrees vs. -1.15 +/- 0.61 degrees ) of the distal fragment in the arrangement without a foot plate compared with the construct with a foot plate. The anterior translation of the distal fragment was similar with (1.12 +/- 0.98 mm) and without a foot plate (1.19 +/- 1.23 mm).


CONCLUSIONS
This study supports the mechanical importance of spanning of the ankle with a foot plate in most cases of external fixation for unstable extra-articular and periarticular distal tibia fractures. Further studies are needed to validate these results before widespread changes in clinical treatment can be recommended.
Antoci
Valentin
V
Department of Orthopedic Surgery, University of Louisville, Louisville, KY 40202, USA.
Voor
Michael J
MJ
Seligson
David
D
Roberts
Craig S
CS
D000368:Aged; D001696:Biomechanical Phenomena; D016267:External Fixators; D005260:Female; D005528:Foot / Q000000981:diagnostic imaging; D005592:Fracture Fixation / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D011859:Radiography; D013978:Tibial Fractures / Q000000981:diagnostic imaging / Q000601:surgery*