Are peroneal tendons safe after intramedullary fibular nailing? A prospective MRI-based cohort

Intramedullary fibular nailing (IFN) offers a minimally invasive alternative to plate fixation for unstable ankle fractures, yet concerns persist regarding potential iatrogenic injury to the peroneal tendons during portal creation. No previous in vivo study has evaluated tendon integrity after IFN using advanced imaging. In this cohort, we examined peroneal tendon morphology and syndesmotic reduction following IFN using serial postoperative magnetic resonance imaging (MRI), comparing findings with a healthy control group.

A prospective cohort of 102 adults with unstable Weber B or C ankle fractures underwent IFN and completed at least eight months of follow-up. All patients received standardized ankle MRI at 3 and 8 months postoperatively. Tendon morphology, signal characteristics, and thickness were assessed by a blinded musculoskeletal radiologist. Syndesmotic reduction was evaluated in patients requiring trans-syndesmotic fixation. A control group of ten healthy volunteers underwent the same MRI protocol. Statistical comparisons were performed using independent-samples t tests and equivalence testing with predefined margins.

Peroneal tendons demonstrated no MRI-detectable pathology at both 3 and 8 months. At 8 months, tendon thickness (peroneal brevis: 2.9 ± 0.3 mm; peroneal longus: 3.4 ± 0.4 mm) was comparable to controls (2.8 ± 0.3 mm and 3.4 ± 0.4 mm; p > 0.37), meeting equivalence criteria (TOST p < 0.001). Among patients requiring syndesmotic fixation (n = 28), tibiofibular alignment remained anatomic (clear space: 3.1 ± 0.4 mm; overlap: 8.7 ± 1.2 mm). Union was achieved in all cases, with no infections or tendon-related symptoms.

Intramedullary fibular nailing preserves peroneal tendon integrity and provides reliable syndesmotic stability when performed with proper technique. Tendon morphology and signals remained indistinguishable from healthy controls, and postoperative alignment was consistently anatomic. These findings support IFN as a safe, biologically respectful option for the treatment of unstable ankle fractures.