Parameter evaluation

Risk factors for redisplacement were evaluated in three aspects, which included patient-related, fracture-related, and cast-related factors. Patient-related data, such as age and gender, were collected from electronic records. Fracture-related factors included distance from epiphysis, associated ulna fracture, translation, angulation, and adequacy of reduction. The adequacy of reduction was classified as anatomic, good, or fair. Anatomic reduction is complete anatomic fracture reduction with no translation or angulation, good reduction is < 10° of dorsal angulation or < 2 mm of translation, and fair reduction is less than a good reduction, with translation of between 2 and 5 mm or angulation of between 10 and 20° or any radial deviation of < 5° or a combination of 5 to 10° of dorsal angulation and < 2 mm of translation. The cast-related factors were cast index, padding index, and gap index. The indices were calculated as described by Bae et al. [18], and a brief description is listed below:

Cast index was estimated by measuring the inside diameter of the plaster in the lateral view as a ratio to the diameter in the AP view at the fracture site;

Gap index: [(radial fracture-site gap + ulnar fracture site gap)/inner diameter of cast in AP plane] + [(dorsal fracture site gap + volar fracture site gap)/inner diameter of cast in lateral plane];

Three-point index: [(distal radial gap + ulnar fracture site gap + proximal radial gap)/contact between fracture fragments in AP plane] + [(distal dorsal gap + volar fracture site gap + proximal dorsal gap)/contact between fracture fragments in lateral plane] (Fig. ​(Fig.22).

The measurement of cast related indices. a, b Cast index. Cast index = b/a. c, d Gap index. Gap index = (c + d)/e + (f + g)/h. e, f Three-point index. Three-point index = (i + j + k)/l + (m + n + o)/p

The radiographs taken after cast application were used for measurement of the various radiographic indices. Two blinded observers assess the radiological findings independently. For continuous variables, the mean values were used. For categorical variables, disagreements between the two observers were settled by discussion, and the third observer made the final decision in the case of no consensus could be reached.