Soft tissue swelling on anterior posterior radiograph predicts subsequent displacement of song 2 lateral humeral condyle fractures.

Introduction: According to the Song classification, the treatment of Song 2 lateral humeral condyle fracture (LHCF) is controversial because the stability of the fracture is difficult to determine. The aim of this study is to investigate whether the swelling of soft tissue on lateral side of elbow could be used as a predictor of the stability of Song 2 fractures.

Materials and methods: A retrospective study of children diagnosed with LHCF admitted to our hospital from January 2017 to March 2023. Fractures were classified by Song classification. Age at onset, laterality, sex, initial treatment and follow-up times were collected. The Swelling value was measured on AP radiograph at two time point of fracture was diagnosed (swelling value 1) and healed (swelling value 2). The Song 2 fractures who underwent conservative treatment at initial were divided into 2 groups according to whether occur subsequent displacement or not: (1) displacement group, (2) nondisplaced group.

Results: A total of 255 patients were enrolled. Swelling value 1 increased with the severity of Song type, and Song 2 significantly smaller than Song 4 and Song 5 (P = 0.002 and 0.000, respectively). Among the 50 Song 2 patients who underwent initial conservative treatment, 28% (14/50) patients occurred subsequent displacement. The swelling value 1 was significantly higher in displacement group than nondisplaced group (54.4%±2.4% vs. 50.3%±3.0%, P = 0.001), and the mean timing of late displacement was 3.9 days (1 to 8). Binary logistic regression analysis showed that swelling value 1 had significant difference (P = 0.003), and a cutoff value of 53.0% of swelling value 1 for subsequent displacement in Song 2 type fracture.

Conclusions: The swelling value correlates with Song type and exhibits an increasing trend, potentially reflecting the integrity of the cartilage hinge indirectly, and it can be a reliable predictor of subsequent displacement for Song 2 fractures.