To investigate the characteristics and reliability of a novel sub-classification of Wilkins type III lateral-flexion supracondylar fracture of the humerus in children.

A retrospective cohort study was used to analyze the clinical data of 92 children with supracondylar fracture of the humerus admitted to Provincial Children′s Hospital of Anhui Medical University from January 2013 to August 2021, including 38 males and 54 females, aged 2-13 years [(8.5±2.4)years]. Lateral-flexion Wilkins type III supracondylar humeral fractures were classified into two subtypes according to the fracture features: type IIIA (n=14), complete fracture with the distal fragment displaced anteriorly and laterally, with no obvious anterior or posterior inclination (<10°) or rotation; type IIIB (n=78), complete fracture with the distal fragment displaced anteriorly and laterally, with significant anterior or posterior inclination (>10°) or rotation. The incidence and risk ratio of ulnar nerve injury and open reduction were compared between the two subtypes of the fracture. The weighted Kappa method was used to test the inter- and intra-observer agreement of the two new subtypes.

Of all, 15 children had ulnar nerve injury, among which 1(6.7%) was type IIIA and 14(93.3%) were type IIIB; while other 77 children had no ulnar nerve injury. The risk of ulnar nerve injury in children with type IIIB was 3-fold higher than that in children with type IIIA (OR=2.84, 95%CI 0.34- 25.56, P>0.05). The open reduction was performed in 11(73.3%) out of the 15 children with ulnar nerve injury, but in 18(23.4%) out of the 77 children with no ulnar nerve injury. The risk of open reduction in children with ulnar nerve injury was 9-fold higher than that in children without ulnar nerve injury (OR=9.01, 95%CI 2.28- 33.17, P<0.01). Open reduction was performed in 29 children, among which 2(6.9%) were type IIIA and 27(93.1%) were type IIIB. The risk of open reduction in children with type IIIB was 3-fold higher than that in children with type IIIA (OR=3.17, 95%CI 0.66-15.24, P>0.05). The intra-observer Kappa value was 0.49±0.09(95%CI 0.31-0.66), indicating a moderate agreement. The inter-observer Kappa value was 0.80±0.06(95%CI 0.68-0.91), indicating a strong or very strong agreement.

Wilkins type IIIB lateral-flexion supracondylar fracture of the humerus in children is more likely to be accompanied by ulnar nerve injury and to be opt to open reduction in comparion with type IIIA. The new subtyping has reliable inter-observer and intra-observer consistency, and is able to facilitate the prediction of surgical plans.

Humeral fractures; Child; Fracture classification