Comparison of Tibial Nail Entry Point Location Among Infrapatellar, Suprapatellar, and Lateral Parapatellar...

Background: Tibial shaft fractures are frequently treated with intramedullary nailing; however, malalignment remains a concern, particularly in proximal metaphyseal fractures. The surgical approach influenced the nail entry point; however, the three-dimensional (3D) geometric characteristics of the entry point among different approaches remain unclear. Methods: This single-center retrospective study included 68 patients with acute tibial shaft fractures (AO/OTA type 42) treated with reamed and locked intramedullary nails from January 2014 to June 2024. The surgical techniques employed included lateral parapatellar (LPA, n = 31), infrapatellar (IPA, n = 27), and suprapatellar (SPA, n = 10) approaches. Postoperative computed tomography (CT) data were reconstructed into standardized 3D images. The mediolateral insertion ratio was calculated as the percentage distance from the lateral tibial plateau edge to the nail entry point relative to the plateau's width in the coronal plane. The shortest distance from the tibial articular surface to the nail (r) was measured in the sagittal plane. The Kruskal-Wallis test and Dunn's post hoc comparisons were used to analyze group differences. Results: Baseline patient and fracture characteristics did not significantly differ among the groups. The mediolateral insertion ratio significantly differed (p < 0.0001), with a more lateral entry for the LPA (44.0% [43.0-47.0]) than for the IPA (51.0% [49.0-53.0], post hoc p < 0.0001) and SPA (49.0% [47.0-51.3], post hoc p = 0.0034). Further, the sagittal distance r significantly differed (p < 0.0001), with a more distal entry for the LPA (14.8 [12.8-20.1] mm) than for the IPA (9.7 [7.0-11.8] mm, post hoc p < 0.0001) and SPA (10.5 [5.5-12.9] mm, post hoc p = 0.0008). No statistically significant difference was observed between the IPA and SPA. Conclusions: The LPA generates a significantly more lateral and distal tibial nail entry point than the IPA and SPA. No statistically significant differences were detected between the IPA and SPA in either plane. These 3D-CT findings may warrant attention during approach selection and guidewire placement, particularly for fractures extending into the proximal metaphysis.