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

The aims of this study were i) to see if there is an association between poorly applied plasters and redisplacement of paediatric forearm fractures, and ii) to define reliable radiographic measurements to predict redisplacement of these fractures. The two radiographic measurements which were assessed were Cast Index and Padding Index which are a guide to plaster moulding and padding respectively. The sum of these was termed as the Canterbury Index. Case records and radiographs of 142 children who underwent a manipulation for a displaced fracture of forearm were studied. Angulation, translation displacement, Cast index and Padding index were measured on radiographs. Redisplacement was seen in 44 cases (32.3%). The means and 95 % Confidence intervals for cast index and padding index were 0.87 (0.84, 0.90) and 0.42 (0.39, 0.62) in the redisplacement group whereas were 0.71 (0.69, 0.72) and 0.11 (0.09, 0.12) in the group with no redisplacement respectively. Initial displacement, Cast index, Padding index and Canterbury Index were significantly greater in the redisplacement group (p< 0.005). No statistically significant difference was seen for age, fracture location, initial angular deformity and seniority of the surgeon. We suggest that Cast Index > 0.8, Padding Index > 0.3 and Canterbury Index > 1.1 are significant risk factors for redisplacement of conservatively treated paediatric forearm fractures

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

Redisplacement is the most common complication of immobilisation in a cast for the treatment of diaphyseal fractures of the forearm in children. We have previously shown that the three-point index (TPI) can accurately predict redisplacement of fractures of the distal radius. In this prospective study we applied this index to assessment of diaphyseal fractures of the forearm in children and compared it with other cast-related indices that might predict redisplacement. A total of 76 children were included. Their ages, initial displacement, quality of reduction, site and level of the fractures and quality of the casting according to the TPI, Canterbury index and padding index were analysed. Logistic regression analysis was used to investigate risk factors for redisplacement. A total of 18 fractures (24%) redisplaced in the cast. A TPI value of > 0.8 was the only significant risk factor for redisplacement (odds ratio 238.5 (95% confidence interval 7.063 to 8054.86); p < 0.001).

The TPI was far superior to other radiological indices, with a sensitivity of 84% and a specificity of 97% in successfully predicting redisplacement. We recommend it for routine use in the management of these fractures in children.

Cite this article: Bone Joint J 2013;95-B:563–7.