# Risk factors associated with delayed union after open reduction and plate fixation for humeral diaphyseal fractures

## TL;DR

This study identifies risk factors for delayed bone healing after surgery for humeral fractures, finding that postoperative complications increase the risk while using interfragmentary screws reduces it.

## Contribution

The study identifies interfragmentary screw use and postoperative complications as novel independent predictors of delayed union in humeral diaphyseal fractures.

## Key findings

- 30.8% of patients experienced delayed union after surgery for humeral fractures.
- Postoperative complications increased the risk of delayed union fivefold.
- Using interfragmentary screws reduced the risk of delayed union by 86%.

## Abstract

The risk factors related to delayed union in humeral diaphyseal fractures (HDFs) following surgical osteosynthesis remain unclear. Therefore, this study aimed to evaluate radiological outcomes and the risk factors associated with delayed union in a retrospective cohort of patients who underwent open reduction and plate fixation (ORPF) for acute HDFs.

Consecutive patients with AO/OTA 12-A and AO/OTA 12-B fractures who underwent ORPF using standard compression techniques between 2017 and 2020 were enrolled in the study. Demographic data, along with serial medical records and radiographs, were collected. The included patients were divided into two groups: the timely union (union occurring within 6 months postoperatively) and the delayed union group (union occurring between 6 and 12 months postoperatively). Differences between the groups were examined, and logistic regression was subsequently applied for risk factor analysis.

Sixty-five cases were included in the study, consisting of 34 males and 31 females, with a median age of 38.9 years. Among these, 45 cases (69.2%) were classified in the timely union group, while 20 cases (30.8%) were classified in the delayed union group. Overall, 30 cases (46.2%) demonstrated secondary bony union. Significant differences were observed between groups in terms of fracture pattern, immediate postoperative fracture gap, union pattern, and complication rate (p < 0.05 for all comparisons). Multivariate logistic regression analysis revealed that the use of interfragmentary screw and the presence of postoperative complications were independent predictors of delayed union, with an adjusted odds ratio of 0.14 and 5.76, respectively.

In ORPF for acute HSFs, 30 out of 65 cases demonstrated secondary bone union despite the use of standard compression techniques. The application of interfragmentary screws significantly reduces the risk of delayed union. Conversely, the presence of postoperative complications is associated with an increased likelihood of delayed union.

Level of evidence: 3

Trial Registration All procedures were approved by the institutional review board of the authors’ hospital (IRB nos. A-ER-112-395 and IRB20230089)

The online version contains supplementary material available at 10.1186/s10195-025-00843-0.