The effect of external coaptation on plate deformation in an ex vivo model of canine pancarpal arthrodesis

Objectives: Since external coaptation is applied clinically to prevent plate failure during healing in canine pancarpal arthrodesis (PCA), we tested the hypothesis that external coaptation does not significantly reduce plate strain in an experimental ex vivo model of canine PCA. Methods: Ten thoracic limbs from healthy Greyhounds euthanatized for reasons un- related to the study were harvested and the carpus was stabilised with a dorsally applied 2.7/3.5 mm hybrid PCA plate. The strain in the plate adjacent to the most distal radial screw hole (R4) and the radial carpal bone (RCB) screw hole was measured as the limbs were loaded axially to a load that approximated that of controlled walking. Each limb was tested with and without external coaptation in place. Results: Mean strain amplitude at the RCB was -177.2 με (± 20.78) without external coaptation. Following cast application, strain reduced significantly to -34.7 με (± 9.84) (p