A Biomechanical Evaluation of a Hybrid Dynamic Compression Plate and a CastLess Arthrodesis Plate for Pancarpal Arthrodesis in Dogs.

OBJECTIVE:
To determine mechanical differences between two plates with different requirements for supplementary casting after pancarpal arthrodesis (PCA): the Veterinary Instrumentation Hybrid Dynamic Compression Plate (HDCP), and the OrthoMed CastLess Arthrodesis Plate (CLP).
STUDY DESIGN:
In vitro mechanical analysis.
SAMPLE POPULATION:
HDCP(n = 10), CLP(10).
METHODS:
Single-cycle load to failure using a materials-testing machine and cyclic loading between 38 and 380 N ± 5% to simulate estimated in vivo loads until failure or 10(6) cycles.
RESULTS:
Single-cycle to failure: bending stiffness was significantly higher for the HDCP(2269 ± 175 N/mm) than CLP(1754 ± 88 N/mm; P < .001). Bending structural stiffness was higher for the HDCP(3.8 ± 0.3 Nm(2) ) versus CLP(2.9 ± 0.2 Nm(2) ; P= .0022). A difference between the 2 plates for bending strength was not demonstrated; HDCP= 13.9 ± 1.4 Nm, CLP13.2 ± 0.5 Nm (P= .24). Cyclic Loading: no failures occurred with either plate type when plates were cycled to 10(6) cycles.
CONCLUSION:
There is no mechanical advantage in bending resistance afforded by the CLPover the HDCP. Fatigue failure of either plate during the convalescent period of an estimated 150,000-250,000 cycles is unlikely. Based on the bending performance, there is no evidence to support the use of the CLPover the HDCPfor castless PCA.