The effects of postoperative malrotation alignment on outcomes of Gartland type III/IV paediatric supracondylar humeral fractures treated by close reduction and percutaneous K-wire fixation

Purpose In this study, we aimed to investigate the effects of postoperative malrotation alignment on the outcomes of Gartland type III/IV paediatric supracondylar humeral fracture (SCHF) treated by close reduction and percutaneous K-wire fixation. Methods Between January 2014 and December 2021, 295 Gartland type III/IV paediatric SCHFs treated by close reduction and percutaneous K-wire fixation were selected for this retrospective study. The demographic, clinical and radiographic parameters of all cases were collected. The lateral rotation percentage (LRP) was measured on X-rays to evaluate postoperative malrotation alignment of the fracture. All cases were categorized into 4 groups according to LRP: LRP ≤ 10% (210, 71.2%), 10% < LRP ≤ 20% (41, 13.9%), 20% < LRP ≤ 30% (26, 8.8%) and LRP > 30% (18, 6.1%). The carrying angle, ranges of multidirectional motions, Mayo Elbow Performance Score (MEPS) and Flynn’s Standard Score (FSS) of the injured elbow were assessed 6 months postoperation and compared among different groups. ROC analysis based on LRP and the excellent/good rate of FSS was performed to determine the acceptable maximum degree of postoperative malrotation alignment. Results There was no difference in the demographic characteristics (age, sex, injured side and fracture type), postoperative Baumann angle, carrying angle or range of forearm rotation among the 4 groups ( P > 0.05). The operation time and time from operation to K-wire removal were longer in the 20% < LRP ≤ 30% and LRP > 30% groups than in the LRP < 10% and 10% < LRP ≤ 20% groups ( P < 0.001). The shaft condylar angle, range of elbow flexion, MEPS and FSS of the injured elbow 6 months postoperatively were lower in the 20% < LRP ≤ 30% and LRP > 30% groups than in the LRP < 10% and 10% < LRP ≤ 20% groups ( P < 0.001). ROC analysis based on LRP and the excellent/good rate of FSS showed an area under the curve of 0.959 (95% CI 0.936–0.983), with a cutoff value of 26.5%, sensitivity of 95.3% and specificity of 90.1%. Conclusion A certain degree of residual malrotation alignment deformity of the SCHF may reduce the shaft condylar angle and extend the time from operation to removing the K-wire and affect elbow function, especially the range of elbow flexion. The acceptable maximum degree of residual malrotation deformity expressed as the LRP value was 26.5%.