No significant differences in nonunion rates between static and dynamic intramedullary nail fixation for non-comminuted femoral shaft fractures

Objectives: The objective of our study was to evaluate whether static or dynamic fixation mode in non-comminuted femoral shaft fractures treated with Intramedullary Nail (IMN) exhibits differences in terms of nonunion. We hypothesize that there is no difference between both groups. Methods: Design: Retrospective. Setting: Level 1 trauma center. Patient Selection Criteria: Patients treated for femoral shaft fractures with IMN. Exclusion criteria included age under 18 years old, polytrauma patients, open fractures, periprosthetic fractures, pathologic fractures, associated lower extremity fractures, fractures involving joint extension, bilateral femoral fractures, or comminuted fractures.Outcome Measures and Comparisons: The primary outcome was the nonunion rate, defined as either a lack of progression in the Radiographic femoral RUST score between two consecutive intervals starting at 6 months or a RUST score of less than 9 points at 12 months. The secondary outcome consists of nonunion rate analysis between groups based on AO/OTA classification subgroups. Results: In total 75 patients with the same number of fractures were included with a mean age of 33.5 years (SD 13.11). 37 (49.3%) patients received statically locked fixation and 38 (50.7%) patients received dynamically locked fixation. The overall nonunion rate was 9.3%, with no significant differences between groups (p = 0.219). Union rates across the AO/OTA classification groups showed statistically significant differences (p = 0.036). However, no differences were observed for the AO/OTA-A (p = 0.423) and AO/OTA-B (p = 0.221) groups when subgroup analysis by locking mode was performed. Good interobserver (ICC= 0.832; 95% CI = 0.66–0.92) and intraobserver (ICC=0.881; 95% CI = 0.79–0.93) reliability of femoral RUST score was found. Conclusion: No significant differences were found in overall nonunion rates between static and dynamic locking IMN fixation in non-comminuted femoral shaft fractures. Similarly, no differences were observed in fixation type when analyzing the AO/OTA-A or B subgroups separately.