Comparison of double dynamic compression plating versus two configurations of an internal veterinary fixation device: Results of in vitro mechanical testing using a bone substitute.
OBJECTIVE
To compare the mechanical properties of 2 configurations of a veterinary fixation system (VFS) for large animal long bones with dynamic compression plating (DCP).


METHODS
Eighteen pairs of Canevasit tubes (Canevasit; Amsler und Frei, Schinznach Dorf, Switzerland) (length, 170 mm; diameter, 47.5 mm; cortex thickness, 10 mm), aligned with a 10-mm gap, and stabilized with 2 DCP or 2 VFS implants.


METHODS
Three groups (n = 6) were compared. Group 1 Canevasit tubes were stabilized with two 10-hole, broad 4.5-mm stainless steel DCP applied with both plates centered over the gap, in orthogonal planes parallel to the long axis of the tubes and staggered to allow bicortical fixation with ten 4.5-mm, 52-mm-long cortex screws each. Group 2 tubes were stabilized similarly with 2 VFS implants, each composed of a stainless steel rod (length, 167 mm; diameter, 8 mm), and 10 clamps were applied in alternating fashion left and right on the rod and fixed bicortically with ten 4.5-mm, 52-mm-long, cortex screws. Group 3 tubes were stabilized similarly, but using only 6 clamps/rod. All groups were tested initially in torsion within elastic limits and subsequently in 4-point bending, with 1 implant on the tension side, until gap closure occurred.


RESULTS
None of the constructs failed, but all had plastic deformation after 4-point bending. No statistically significant differences were found among the 3 groups in torsional stiffness. Double DCP fixation was significantly stiffer and stronger in 4-point bending, compared with both configurations of double VFS fixation.


CONCLUSIONS
The plate design was favored in this study. The VFS system may have to be adapted before further tests are conducted. Test modalities have to be chosen closer to clinical conditions (real bone, cyclic loading, closed gap).


CONCLUSIONS
The veterinary fixation system has not yet proven its advantages for large animal long bone fracture repair. From the pure mechanical point of view, double DCP is the favored method for the treatment mentioned.
Haerdi-Landerer
Christina
C
AO Research Institute, Davos, Switzerland.
Steiner
Adrian
A
Linke
Berend
B
Wahl
Dieter
D
Schneider
Erich
E
Hehli
Markus
M
Frei
Reto
R
Auer
Jörg A
JA
D000818:Animals; D001696:Biomechanical Phenomena; D001860:Bone Plates / Q000662:veterinary*; D019245:Compressive Strength; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D008422:Materials Testing / Q000662:veterinary; D019736:Prostheses and Implants / Q000662:veterinary*