Ultrasound-guided cross-pin technique for paediatric supracondylar humerus fractures: minimizing iatrogenic ulnar nerve injury

Previous ultrasound-guided cross-pin techniques, which employ 90° elbow flexion, have demonstrated effectiveness; however, they may be associated with an elevated risk of iatrogenic ulnar nerve subluxation or dislocation. The aim of this study was to evaluate the efficacy and safety of a modified ultrasound-guided cross-pin technique for reducing the risk of iatrogenic ulnar nerve injury in paediatric patients with supracondylar humerus fractures. This retrospective study was conducted from December 2017- October 2019 and included paediatric patients with displaced supracondylar humerus fractures. The modified ultrasound-guided cross-pin technique was utilized to identify the ulnar nerve and confirm the medial pin position during pin placement with elbow in extension. The primary outcome measure was the incidence of iatrogenic ulnar nerve injury. A total of 145 patients (mean age 5.8 years) were enrolled. There were 103 children with Gartland type III fractures, 35 with type II fractures, and 7 with type IV fractures. The incidence of iatrogenic ulnar nerve injury was significantly reduced to 0%. A total of 12 cases had abnormal pin insertions, including 11 cases in which the proximity of the inserted medial pin to the ulnar nerve was close and 1 case in which the ulnar nerve was directly violated by the pin. The rate of pin misplacement was 8.3%. At the latest follow-up, all patients demonstrated excellent and good functional outcomes according to the Flynn criteria. The ultrasound-guided cross-pin technique may serve as a viable alternative for reducing the risk of iatrogenic ulnar nerve injury in paediatric patients with supracondylar humerus fractures.