Closed reduction and percutaneous pinning has become the most common technique for the treatment of Type III displaced supracondylar humerus fractures in children. The purpose of this study was to evaluate whether the loss of reduction in lateral K wiring is non-inferior to crossed K wiring in this procedure.

A prospective randomised non-inferiority trial was conducted. Patients aged three to seven presenting to the Emergency Department with a diagnosis of Type III supracondylar humerus fracture were eligible for inclusion in the study. Consenting patients were block randomised into one of two groups based on wire configuration (lateral or crossed K wires). Surgical technique and post-operative management were standardised between the two groups. The primary outcome was loss of reduction, measured by the change in Baumann's angle immediately post –operation compared to that at the time of K wire removal at three weeks. Secondary outcome data collected included Flynn's elbow score, the humero-capitellar angle, and evidence of iatrogenic ulnar nerve injury. Data was analysed using a t-test for independent means.

A total of 52 patients were enrolled at baseline with 23 allocated to the lateral pinning group (44%) and 29 to the cross pinning group (56%). Six patients (5 crossed, 1 lateral) received a third wire and one patient (crossed) did not return for x-rays at pin removal and were therefore excluded from analysis. A total of 45 patients were subsequently analysed (22 lateral and 23 crossed). The mean change in Baumann's angle was 1.05 degrees, 95% CI [-0.29, 2.38] for the lateral group and 0.13 degrees, 95% CI [-1.30, 1.56] for the crossed group. There was no significant difference between the groups in change in Baumann's Angle at the time of pin removal (p = 0.18). Two patients in the crossed group developed post-operative iatrogenic ulnar nerve injuries, while none were reported in the lateral group.

Preliminary analysis shows that loss of reduction in Baumann's angle with lateral K wires is not inferior to crossed K wires in the management of Type III supracondylar humerus fractures in children. The results of this study suggest that orthopaedic surgeons who currently use crossed K wires could consider switching to lateral K wires in order to reduce the risk of iatrogenic ulnar nerve injuries without significantly compromising reduction.