title: The effect of external coaptation on plate deformation in an ex vivo model of canine pancarpal arthrodesis.
abstract: OBJECTIVE
  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 <0.002). Mean strain at R4 was -89.4 με (± 22.10) without external support and -66.9 με (± 10.74) following application of a cast. This reduction in recorded strain was not statistically significant.
  
  
  CONCLUSIONS
  The application of a cast to the distal portion of the limb significantly reduced strain in the 2.7/3.5 mm hybrid PCA plate, but the magnitude of the measured strain was low, suggesting that fatigue damage is unlikely to accumulate as a result of this type of loading and that external coaptation may not be necessary to prevent fatigue failure of the plate.
authors: Royal Dick School of Veterinary Studies, Division of Veterinary Clinical Sciences, The University of Edinburgh, Hospital for Small Animals, Easter Bush Veterinary Centre, Roslin, Midlothian EH259RG, Scotland. samantha.woods@ed.ac.uk
authors: S
authors: S
authors: Woods
authors: R J
authors: RJ
authors: Wallace
authors: J R
authors: JR
authors: Mosley
mesh_terms: D000818:Animals; D001174:Arthrodesis / Q000662:veterinary*; D001696:Biomechanical Phenomena; D001860:Bone Plates / Q000662:veterinary*; D002102:Cadaver; D002350:Carpus, Animal / Q000601:surgery*; D004285:Dogs; D008422:Materials Testing