Screw Fixation of the Posterior Malleolus Fragment in Ankle Fracture: Cadaveric and Clinical Studies

CATEGORY: Ankle, Trauma INTRODUCTION/PURPOSE: Previously, a posterior malleolus fragment (PMF) covering 25–30% of the articular surface was a known indication for surgical fixation for ankle fractures. This study aimed to compare the outcomes of screw fixation for PMF comprising <25% of the articular surface and to evaluate the results of cadaver experiments. METHODS: The clinical study enrolled ankle fracture patients with PMFs who planned to undergo surgery between March 2014 and February 2017. Among them, 62 with type 1 PMF comprising <25% of the articular surface were included: 32 patients underwent cannulated screw fixation for PMF after fixation for lateral and/or medial malleolar fracture (A group), whereas the other 30 patients underwent internal fixation for lateral and/or medial malleolar fracture but no screw fixation (B group). Clinical outcomes were determined at the 3-, 6-, 12-, and 18-month visits. Additionally, cadaver studies were conducted to evaluate cannulated screw fixation or no fixation in cases of PMFs comprising <25% of the articular surface and >1 mm displacement. Ankle joint stability was measured under external torque on the ankle in the neutral position. The level of significance was set at P < .05. RESULTS: Clinical outcomes at 6 and 12 months after surgery were significantly higher in group A than in group B. However, there was no significant intergroup difference in clinical outcomes at 18 months of follow-up. In the cadaver study, PMF screw fixations were significantly more stable under external rotation force. CONCLUSION: Screw fixation was significantly useful during early recovery and in short-term clinical outcomes owing to stabilization of ankle fractures with PMF involving <25% of the articular surface.