REPRODUCIBILITY, REPEATABILITY AND FACE VALIDITY OF A MODEL OF A DISTAL RADIUS FRACTURE

Aims: The distal radius fracture model prototype has been produced as a means for teaching reduction of a distal radius fracture. In this study we aim to test the repeatability and reproducibility of the force required to correct the shortening of the radius. In addition a questionnaire was carried out to assess face validity Methods and materials: The distal radius fracture model prototype has been designed and manufactured to simulate reduction of a dorsally displaced, radially angulated, shortened fracture of the distal radius. We designed a mounting rig for the model and used a Hounsfield tensometer to measure the degree of movement of the distal fracture fragment when various degrees of force were applied. Force was applied to reproduce correction of radial shortening. Reproducibility was tested by resetting of the tensioning device at the rear of the model. The questionnaire was constructed using a series of 5 point, verbally anchored Likert items. Results: Mean force required for reduction was 191.4 N (Newton) (range 189.4 – 193.4N). Standard deviation for repeated measurement was 1.65 N. Graphs of force versus extension showed one consistent point of slippage which could be explained by movement in the spring tensioner for distal radial displacement. On repeated testing the model tensioning device also showed good reproducibility of results. The results for face validity showed that most people rated the model as having an appearance consistent with that of a fractured distal radius (median score for appearance 4.7, tactile propertied 4.7) but that the biomechanical properties of the reduction were not scored as highy (median score 3.9) The median score when asked about the usefulness of the model for teaching junior staff was high (4.52) Conclusions: This prototype produces repeatable performance parameters on reduction of the fracture. Overall experience with the prototype is good but it requires further refinement.