Late displacement after lateral condylar fractures of the humerus

Nondisplaced or slightly displaced lateral condyle fractures may subsequently displace if treated with cast immobilization alone, and displacement indicates surgery. In this context, placing the forehand in pronation is sometimes recommended, and the prediction of the late displacement based on the presence of the fat pad sign is useful. However, few studies have quantitatively shown the relationships between forearm position during immobilization and late displacement and between the presence of the fat pad sign and late displacement. We investigated the factors that may affect the late displacement and the features of the consequences during the late displacement.Between October 2003 and July 2020, we observed 62 patients (45 boys and 17 girls). We evaluated the correlation between the factors age, gender, the initial displacement, the presence of a fat pad sign, the flexion angle of the elbow, the forearm position (pronation or neutral), and the late displacement on day 7 after the injury, which means the difference between the displacement on day 0 and that on day 7 in the 62 cases with the minimal displacement. Moreover, of all 62 cases observed, we further investigated those 52 cases that had been treated conservatively for 3 weeks for any resultant effects. We used the Friedman test to evaluate the difference in the late displacement on each day. We acknowledged the P value < .05 as significant.There was no significant correlation between each factor (age, sex, initial displacement, presence of the fat pad sign, flexion angle of the elbow, or forearm position) and displacement on day 7, whereas there was significant progressive displacement until day 7.The present study concluded that late displacement would happen until the 7 postoperative dates, regardless of the splint angle, the fat pad sign, the age, or the gender. Therefore, it is important to follow any case, even with mild-displaced lateral condylar humeral fractures, until day 7 because the late displacement might occur.