Non-rotational medial pinning with the K-Hammer technique in pediatric supracondylar fractures: a retrospective case-control study.

BACKGROUND

Pediatric Gartland type III-IV extension-type supracondylar humeral fractures are associated with a risk of iatrogenic ulnar nerve injury during medial percutaneous pin insertion. The optimal technique for medial pin placement during crossed pin fixation remains debated.

METHODS

A retrospective case-control study was conducted involving 80 pediatric patients treated between September 2020 and September 2025. All patients had isolated closed extension-type Gartland III-IV supracondylar humeral fractures treated with two lateral and one medial crossed K-wires, with a minimum follow-up of 6 months. Patients were divided into the K-Hammer group, in which medial pinning was performed using a non-rotational K-Hammer-assisted technique with the elbow in 30°-60° extension, and the Freehand group, in which medial pinning was performed using conventional low-speed drilling with the elbow flexed at 90°. The primary outcome was symptomatic iatrogenic ulnar nerve injury within 2 weeks postoperatively. Secondary outcomes included medial pin attempts, operative time, radiographic alignment, elbow range of motion, Flynn functional grade, and postoperative complications.

RESULTS

The K-Hammer group had significantly fewer medial pin attempts [1.0 (IQR: 1.0-1.0) vs. 2.0 (IQR: 1.0-2.0), P < 0.001] and shorter operative time (32.8 ± 6.9 vs. 37.9 ± 9.2 min, P = 0.006). Intraoperative pink pulseless hand rates were comparable (10.5% vs. 4.8%, P = 0.416), and all patients recovered radial pulse postoperatively. Iatrogenic ulnar nerve injury occurred in 0% (0/38) of the K-Hammer group vs. 11.9% (5/42) of the Freehand group (P = 0.056), corresponding to an exploratory absolute risk reduction (ARR) of 11.9% and a number needed to treat (NNT) of approximately 8.4. No secondary displacement or reoperation occurred in either group. Pinsite infection and myositis ossificans rates were low and similar. At a median follow-up of 7.5 months (IQR: 6.2-11.8; range: 6-36 months), radiographic and functional were comparable between groups.

CONCLUSIONS

The K-Hammer technique improves operative efficiency, reduces pin insertion attempts, and demonstrates a favorable trend toward reduction in iatrogenic ulnar nerve injury risk (ARR 11.9%, NNT = 8.4), without compromising radiographic or functional outcomes. Although statistical significance was not reached (P = 0.056), likely due to limited sample size, these findings suggest it is a potential technical option for medial pin placement in severe pediatric supracondylar humeral fractures, warranting confirmation in larger prospective studies.