Tehran University of Medical Sciences Journal of Orthopedic and Spine Trauma 2538-2330 12 4 2026 09 23 197 203 Erfan Eslami Orthopedic Surgeon, Department of Orthopedic Surgery, Clinical Research Development Center, Imam Hossein Educational Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Ali Pourmojarab Assistant Professor, Department of Orthopedic Surgery, Clinical Research Development Center, Imam Hossein Educational Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Hassan Barati Clinical Research Development Center, Imam Hossein Educational Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran Yousef Fallah Associate Professor, Department of Orthopedic Surgery, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Bahareh Nezhad Mohammad Orthopedic Surgeon, Bone and Joint Reconstruction Research Center, Department of Orthopedics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Mojtaba Baroutkoub Assistant Professor, Department of Orthopedic Surgery, Clinical Research Development Center, Imam Hossein Educational Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2026 06 12 2026 09 06 Background: The optimal fixation method for humeral shaft fractures remains debated. This study compared functional and clinical outcomes after intramedullary nailing (IMN) and open reduction and internal fixation (ORIF) with plate fixation. Methods: In this prospective, observational, comparative cohort study, 85 adults with Arbeitsgemeinschaft für Osteosynthesefragen/Orthopedic Trauma Association (AO/OTA) type 12-B or 12-C humeral shaft fractures were enrolled at a tertiary orthopedic trauma center in Tehran, Iran, between April 2020 and April 2024. Patients underwent IMN (n = 43) or plate ORIF (n = 42) according to the treating surgeon’s judgment. The primary outcome was the 12-month Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) score; secondary outcomes included shoulder and elbow function, pain, union, hospital stay, return to work, and complications. Results: Mean age was higher in the IMN group compared to the ORIF group (41.53 ± 14.12 vs. 35.83 ± 11.82 years; P = 0.047). The duration of hospital stay was shorter after IMN in the unadjusted comparison (2.07 ± 0.34 vs. 2.26 ± 0.59 days; P = 0.043). Nonunion occurred in 2 patients in each group (4.7% vs. 4.8%, P > 0.999), and no statistically significant difference was observed in the unadjusted QuickDASH scores (10.93 ± 11.33 vs. 16.48 ± 15.23; P = 0.060). In an exploratory model adjusted only for age and sex, IMN was associated with a modestly lower QuickDASH score [B = −6.22, 95% confidence interval (CI): −12.20 to −0.25; P = 0.041]; this association remains susceptible to residual confounding. Both techniques achieved high union rates and favorable 12-month outcomes. The unadjusted QuickDASH comparison was not significant, and the modest association in a partially adjusted exploratory model should not be interpreted as clinical superiority of IMN. Treatment selection should remain individualized. https://jost.tums.ac.ir/index.php/jost/article/view/821 https://jost.tums.ac.ir/index.php/jost/article/download/821/487