Purpose:. Paediatric forearm fractures are commonly seen and treated by closed reduction and plaster cast application in theatre. Historically, cast application has been subjectively evaluated for its adequacy in maintaining fracture reduction. More recently emphasis has been placed on objectively evaluating the adequacy of cast application using indicators such as the Canterbury index (CI). The CI has been used in predicting post-reduction, re-displacement risk of patients by expressing the casting and padding indices as a ratio. The CI has been criticized for not including cast 3 point pressure, fracture personality and lack of standardization of X-ray views as well as practical requirement of physical measurement using rulers. The aim of this study was to determine whether subjective evaluation of these indices, on intra-operative fluoroscopy and the day 1 to 7 postoperative X-ray, was accurate in predicting a patient's ultimate risk of re-displacement, following reduction and casting. Materials and Methods:. In total, 22 X-rays from 11 patients were evaluated by 20 orthopaedic registrars and 8 consultants, before and after a tutorial on the Canterbury index. Results:. Formal tutorial did not show an increased subjective predictive accuracy. No clear correlation could be demonstrated between CI and the clinical outcome. Conclusion:. Value of the CI in clinical practice is doubtful due to various confounding factors. The CI has been used due to lack of other available systems, and ideally a system should be sought which incorporates fracture personality, cast 3 point pressure and standardisation of X-Rays

We present an objective method for predicting the redisplacement of paediatric forearm and wrist fractures. Novel radiographic measurements were defined and their value assessed for clinical decision making. In Phase I of the study we defined the cast index and padding index and correlated these measurements with the incidence of fracture redisplacement. Phase II assessed these indices for their value in clinical decision making. Cast Index (a/b) is the ratio of cast width in lateral view (a) and the width of the cast in AP view (b). Padding Index (x/y) isthe ratio of padding thickness in the plane of maximum deformity correction (x) and the greatest interosseous distance (y) in AP view. The sum of cast index and padding index was defined as the Canterbury Index. In Phase I, 142 children's radiographs were analysed and a statistically significant difference was identified between redisplacement and initial complete off-ending of the bones, cast index > 0.8 and padding index of > 0.3. There was no significant association with age, fracture location, seniority of surgeon or angulation. In Phase II, radiographs of 5 randomly selected cases were presented to 40 surgeons (20 consultants & 20 registrars). Following an eyeball assessment they were asked to measure the cast index and padding index (after instruction). With eyeballing the consultants predicted 33% and registrars 25% of the cases that redisplaced. After learning to measure the indices the accuracy increased to 72% for consultants and 81% for registrars (p<0.001). We conclude that the cast index, padding index and Canterbury Index are validated tools to assess plaster cast quality and can be used to predict redisplacement of paediatric forearm fractures after manipulation. They can easily be taught to orthopaedic surgeons and are more accurate than eyeballing radiographs in the clinical setting. Redisplacement can be predicted if cast index > 0.8, padding index > 0.3 and Canterbury Index > 1.1