The effect of a new subtype classification system on prognosis and outcome analysis in pediatric extension-type Gartland type III distal humerus supracondylar fractures

Abstract

The aim of this study was to investigate the association of a new, isthmus-referenced subtype classification system with prognosis and clinical-radiological outcomes in pediatric extension-type Gartland type III distal humerus supracondylar fractures. A total of 145 pediatric patients (mean age: 7.60 ± 2.60) treated with closed reduction and percutaneous pinning for Gartland type III supracondylar humerus fractures between June 2016 and June 2020 were retrospectively reviewed. Fractures were divided into three subgroups based on their relation to the distal humeral isthmus (olecranon fossa): “high zone,” “isthmus zone,” and “low zone”. Operative time, number of K-wires used, radiological angles, and clinical outcomes at 24 weeks (using the modified Flynn grading system) were compared between the groups. The classification demonstrated high interobserver reliability (Kappa: 0.851). Fractures in the ‘high zone’ required significantly shorter operative times and fewer K-wires compared to the other groups (p < 0.001). While radiological angles were similar across groups, the ‘high zone’ group achieved significantly better functional outcomes (78.1% excellent rate). Conversely, the rate of ‘unsatisfactory’ results was significantly higher in the isthmus (25%) and low (31.6%) zones compared to the high zone (4.4%) (p < 0.001). The proposed isthmus-referenced subtype classification demonstrated high interobserver reliability and was associated with operative complexity and 24-week clinical outcomes. Isthmus-zone and low-zone fractures were associated with longer operative times, the use of more K-wires, and a higher frequency of unsatisfactory outcomes than high-zone fractures. This classification may support preoperative planning and risk stratification, although prospective validation is required.