Association between isolated fibular fracture displacement and deep deltoid injury: A comparative analysis of arthroscopic and radiographic assessments

Abstract

Background: Isolated distal fibular fractures can often be successfully treated without surgery. Fracture stability is largely dependent on an intact deep deltoid ligament, yet methods of determining ligament integrity remain a clinical challenge. Recently, fibular fracture displacement on radiographs has been used to predict deep deltoid disruption.

Purpose: To determine whether distal fibular fracture displacement is a reliable indicator of fracture stability based on arthroscopic assessment of deep deltoid ligament integrity.

Study design: This retrospective study evaluated isolated fibular fracture displacement on radiographs in 85 patients at a single medical center. All patients underwent surgical repair of the fracture and arthroscopic evaluation of the deep deltoid.

Methods: Anterior to posterior fibular fracture displacement (APD) and lateral fracture displacement (LFD) were measured and correlated with deep deltoid integrity at each millimeter (mm) of displacement.

Results: Fifty-seven (67 %) patients had an intact deep deltoid, with a median APD of 0.8 mm (range 0.0 - 3.7 mm). Twenty-eight (33 %) patients had a ruptured deep deltoid, with a median APD displacement of 1.85 mm (range 1.05 - 2.7 mm). The deep deltoid was intact over a wide range of fracture gap measurements. The APD was significantly greater in patients with a ruptured deep deltoid (p < 0.001).

Conclusion: Although there was a significant increase in fracture displacement when the deep deltoid was compromised, large APD gap distances did not consistently correlate with a deep deltoid rupture. Anterior to posterior fracture gap distance is not a reliable indicator of deltoid ligament integrity in isolated distal fibula fractures.

Keywords: Ankle fracture; Ankle mortise integrity; Deltoid ligament; Fibular displacement; Stress radiograph.