Early Weightbearing After Operatively Treated Trimalleolar Ankle Fractures with Large Posterior Malleolar Fragments

Abstract

Category: Trauma Introduction/Purpose: No consensus exists regarding postoperative rehabilitation protocols after surgical fixation of unstable trimalleolar ankle fractures with large posterior malleolar fragments. Additionally, no consensus exists regarding type of fixation of large posterior malleolar fragments in these fractures. It is unclear whether clinical results with early weightbearing differ between large posterior malleolar fragments fixed with either screws alone or a plate and screws construct. We evaluated fracture displacement with simulated early weightbearing in a cadaveric model. Methods: Sixteen fresh-frozen lower extremities were assigned to Group 1, trimalleolar ankle fracture with a large posterior malleolar fragment fixed with screws (n=8) or Group 2, trimalleolar ankle fracture with a large posterior malleolar fragment fixed with a plate and screws construct (n=8). Both Groups were tested with an axial compressive load at 3.2 Hz from 100 to 1,000 N and internal/external torque at 1.6 Hz at 0.5 Nm for 250,000 cycles to simulate 5 weeks of full weightbearing. Displacement was measured by differential variable reluctance transducer. Results: The average motion at all fracture sites in both groups was less than 1 mm. Group 1 displacement of the medial, lateral, and posterior malleolar fracture was 0.30 ± 0.27 mm, 0.12 ± 0.11 mm, and 0.87 ± 0.68 mm respectively. Group 2 displacement of the medial, lateral, and posterior malleolar fracture was 0.78 ± 1.52 mm, 0.12 ± 0.16 mm, and 0.87 ± 1.20 mm respectively. There was no significant difference between the average motion at all fractures sites between Group 1 and Group 2 (P > 0.05). There was no statistical correlation between fracture displacement and bone mineral density. Conclusion: This study supports early weightbearing after surgical fixation of unstable trimalleolar ankle fractures regardless of type of fixation of the posterior malleolus. Further investigation of early weightbearing protocols after surgical fixation of unstable trimalleolar ankle fractures are needed to help guide future treatment.