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.