External Fixation vs Plaster Splintage in Maintaining Reduction of PER Stage 3 Ankle Fracture Dislocations; A Cadaveric Study

Purpose: Unstable bimalleolar ankle fractures are a common injury. Typical initial treatment involves closed reduction with splinting. Occasionally the ankle is so unstable that external fixation is used to provide increased stability to the reduced ankle. In such cases the patient is subjected to additional anesthesia risks and pin site infections. Our study assesses the biomechanical difference between stabilization modalities. Our null hypothesis is that external fixation does not provide increased stability compared to plaster splintage in treatment of Pronation External Rotation (PER) type 3 fractures. Methods: Using 7 cadaveric limbs we simulated PER stage 3 bimalleolar ankle fractures and applied plaster splintage or delta frame style external fixation to the fracture-dislocations. A pronatory/external rotation force was applied to the splinted ankles until the talus was dislocated (defined as greater than 50% displaced of the talus relative to the tibia). The stabilization modality was then removed and the process was repeated using the alternative method of stability on each limb. Results: The mean load to failure in the splintage group was 14 lbs. while the external fixation group had a load to failure of 10.14 lbs (p-value = .03). There was no significant difference in load to failure between plaster being applied first to the limbs (p-value = .83) nor if external fixation was applied first (p-value = .67) Conclusions: From our results we can conclude that plaster splintage provided greater stability than delta frame style external fixation in maintaining PER ankle fractures post reduction.