Hybrid external fixation of the proximal tibia: strategies to improve frame stability.
OBJECTIVE
To determine the specific frame construction strategies that can increase the stability of hybrid (ring with tensioned wires proximally connected by bars to half-pins distally) external fixation of proximal tibia fractures. DESIGN Repeated measures biomechanical testing.


METHODS
Laboratory.


METHODS
Composite fiberglass tibias.


METHODS
Using the Heidelberg and Ilizarov systems, external fixators were tested on composite fiberglass tibias with a 1-cm proximal osteotomy (OTA fracture classification 41-A3.3) in seven frame configurations: unilateral frames with 5-mm diameter half-pins and 6-mm diameter half-pins; hybrid (as described above), with and without a 6-mm anterior proximal half-pin; a "box" hybrid (additional ring group distal to the fracture connected by symmetrically spaced bars to the proximal rings) with and without an anterior, proximal half-pin; and a full, four-ring configuration. Each configuration was loaded in four positions (central, medial, posterior, and posteromedial).


METHODS
Displacement at point of loading of proximal fragment.


RESULTS
The "box" hybrid was stiffer than the standard hybrid for all loading positions. The addition of an anterior half-pin stiffened the standard hybrid and the "box" hybrid.


CONCLUSIONS
The most dramatic improvements in the stability of hybrid frames used for proximal tibial fractures result from addition of an anterior, proximal half-pin.
Roberts
Craig S
CS
Department of Orthopaedic Surgery, University of Lousville, Lousville, Kentucky 40202, USA. craig.roberts@lousville.edu
Dodds
James C
JC
Perry
Kelvin
K
Beck
Dennis
D
Seligson
David
D
Voor
Michael J
MJ
D001696:Biomechanical Phenomena; D004867:Equipment Design; D016267:External Fixators; D013978:Tibial Fractures / Q000601:surgery*