2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


Effects of Fibular Plate Fixation and Deep Posterior Deltoid Ligament Repair on Ankle Stability in a Weber B Fracture Model With Complete Deltoid Ligament Sectioning

Andreas Fagerhaug Dalen, MD NORWAY
Martin Greger Gregersen, MSc, Gressvik NORWAY
Aleksander Larsen Skrede, MSc, Aalesund, More og Romsdal NORWAY
Øystein Bjelland, MSc, Aalesund NORWAY
Fredrik Nilsen, Md, PhD, Gressvik NORWAY
Alf Inge Inge Hellevik, MD, PhD, Aalesund NORWAY
Marius Molund, MD, PhD, Gressvik NORWAY

Department of Research and Innovation, Møre and Romsdal Hospital Trust, ÅLESUND, NORWAY

FDA Status Cleared

Summary

Surgical treatment of the unstable Weber B ankle fracture – does fibular plate fixation provide sufficient ankle stability? Robotic testing with biomechanics of different repair methods on ankle specimens

Abstract

BACKROUND
Weber B ankle fractures with complete deltoid ligament rupture are typically considered unstable and treated with plate fixation of the fibula. Recent studies have suggested a significant ankle-stabilizing role of the deep posterior deltoid ligament (dPPTL), which questions current practice. There are few studies on biomechanical effects of plate fixation, and none on dPPTL repair. Therefore, this study aims to evaluate the effects of fibular plate fixation and dPPTL repair on ankle stability in a Weber B fracture model with complete deltoid ligament sectioning.

Methods

Robotic testing of 15 cadaveric ankle specimens in five states: native joint, SER4b injury models, SER4b injury models with plate fixation and dPTTL repair, both individually and combined. Ankle stability where tested in three talocrural joint positions: 10 degrees dorsiflexion, neutral position and 20 degrees plantarflexion, and was measured by the robot in lateral translation, valgus and internal and external rotation. Talar shift and talar tilt in the talocrural joint were measured on mortise view radiographs. The primary outcome was talar shift in neutral ankle position.

Results

When comparing SER4b injury models with plate fixation to native ankles, considerable instability were observed with a mean difference in talar shift of 1.18 mm (95% CI 0.88 to 1.48, P = <.001) and talar tilt of 14.47 degrees (95% CI 12.90 to 16.05, P = <.001). SER4b injury models with combined plate fixation and dPTTL repair showed minor instability, with a mean difference in talar shift of 0.23 mm (95% CI -0.07 to 0.54), P = <.001) and talar tilt of 1.65 degrees (95% CI 0.07 to 3.22, P = <.001) when compared to native ankles.

Conclusion

The main finding of this study was that plate fixation did not considerably enhance ankle stability in SER4b injury models. When combining plate fixation and dPTTL repair, ankle stability was substantially improved.

CLINICAL RELEVANCE
This study provides new insights into the biomechanical effects of plate fixation and dPTTL repair, both individually and combined, for SER4b ankle fractures. This may be useful in development of treatment strategies for these fractures.