Cast revision is effective for critical three-point index values in paediatric forearm fractures: a prospective study

Three-point index (TPI) has been reported to be effective in predicting the displacement of forearm fractures. The aim of this prospective study was to investigate the clinical efficacy of recasting critical but acceptable casts according to three-point index (0.6 < TPI < 0.8) before a redisplacement occurs in childhood forearm fractures. A TPI of 0.6-0.8 was determined in 68 patients, and these were separated as group 1 (n = 34) applied with prophylactic recasting and group 2 (n = 34) where treatment was continued with same cast. The remaining 28 patients had TPI < 0.6 and were assigned as group 3. Groups were compared in respect of age, initial displacement, cast type, location of fracture, initial and late three-point index values and inter- and intraobserver reliabilities of TPI measurements. Significantly less displacement was seen in group 1 than in group 2 (P = 0.004). It was found that a 0.1 increase of index value in the initial and late TPIs increases the probability of redisplacement by 5.06 and 7.78 times, respectively. Late TPI, measured 1 week after casting, had better predictive value than the initial TPI with a sensitivity of 77.8%, specificity of 92.3%, positive predictive value of 70% and negative predictive value of 94.7%. Patients in the grey zone will be able to safely complete the cast treatment with prophylactic recasting without surgical intervention. TPI should be remeasured at the end of first week, as its predictive value becomes more accurate after swelling subsides.