Risk Factors for Symptomatic Nonunion Following Medial Humeral Epicondyle Fracture Fixation in Children

ABSTRACT Background Displaced medial humeral epicondyle fractures (MHEFs) are managed using various surgical approaches. Nonunion can be a serious postoperative complication, but its incidence and risk factors are not well-defined in children. This study aimed to determine the incidence of symptomatic nonunion following the operative management of pediatric MHEFs and to identify associated risk factors. Methods This single-center retrospective study included patients 4-18 years old who underwent open reduction and internal fixation for a MHEF between 2012-2024. Patients with a prior ipsilateral MHEF, multi-limb trauma, or <3 months of postoperative follow-up were excluded. Patient information was obtained from the electronic medical record. Fracture characteristics and fixation techniques were retrieved from operative reports and assessed on imaging. Symptomatic nonunion was defined based on clinical assessment and radiographic appearance. Statistical analysis was performed using Wilcoxon and Fischer tests. Results Among the 322 patients included, six (1.9%) developed symptomatic nonunion and five (1.6%) underwent revision surgery. Patient demographics and skeletal maturity were not identified as risk factors for nonunion. Mechanism of injury, concomitant fractures, and ligament involvement were not associated with nonunion risk. On imaging, fracture fragment size and displacement were not risk factors for nonunion. Regarding surgical technique, neither fixation technique nor difficulty affected nonunion rates. In patients treated with single screw fixation, screw diameter, length, cannulation, threading, and position within the medial epicondyle were not associated with nonunion. However, nonunion was significantly more common when screw-and-washer constructs were not fully seated against the medial epicondyle (p=0.044). Lastly, postoperative duration of rigid immobilization and participation in physical or occupational therapy did not affect nonunion risk. Conclusions The development of symptomatic nonunion after MHEF fixation is rare and difficult to predict. However, our results suggest that inadequate screw compression is a risk factor for nonunion. Given the potentially serious clinical implications of nonunion, further research is needed to determine the optimal compression force that maximizes the likelihood of union while avoiding medial epicondyle fragmentation when using compression screws with or without a washer. Levels of Evidence III, retrospective comparative study Key Concepts • The development of nonunion after the surgical fixation of medial humeral epicondyle fractures is rare and difficult to predict. • Inadequate screw compression is a risk factor for nonunion. • Given the serious clinical implications of nonunion, further research is needed to determine the optimal compression force that maximizes the likelihood of union while avoiding medial epicondyle fragmentation when using compression screws with or without a washer.