Pediatric supracondylar humeral fractures： a safe entry zone of medial pinning based on intraoperative fluoroscopy to avoid iatrogenic ulnar nerve injury

Abstract

Abstract Background For children with supracondylar humeral fractures (SHFs), iatrogenic ulnar nerve injury resulting from medial pinning remains a challenge for orthopedic surgeons. This study aims to explore a safe medial pinning zone and assess its efficacy. Methods First, the radiographic images of a healthy elbow were reconstructed and mapped by E3d software to display the safe medial pinning zone we summarized. Second, all the pediatric SHF cases treated by our team between May 2014 to May 2020 were retrospectively reviewed to evaluate the safety and efficacy of the pinning zone. Furthermore, we proposed a hand gesture to fast locate the safe medial pin insertion point. Results On the anteroposterior (AP) view, the upper 1/2 part of the slope line segment we defined was safe since the ulnar nerve traversed the ulnar groove at the lower 1/2 part. On the lateral view, the diamond zone we defined was a safe entry zone. In the retrospective study, 134 SHF cases were included and divided into two groups. In group A (74 cases), the medial Kirschner wire (K-wire) was inserted from the safe zone at both AP and lateral views, while in group B (60 cases) the medial pinning point was beyond the safe entry zone. The incidence of iatrogenic ulnar nerve injury in group A was significantly lower than in group B (P < 0.01). Moreover, the exploration and neurolysis of the ulnar nerve were performed in patients involving postoperative ulnar nerve dysfunction. A left-hand gesture by the surgeon during operations could help to fast locate the safe insertion point of medial pins. Conclusion Medial pinning from the safe entry zone based on intraoperative fluoroscopy is an easy, reliable, and reproducible technique to avoid iatrogenic ulnar nerve injury in children with SHFs.