Can Lateral X-Rays Reliably Determine Which Posterior Malleolus Ankle Fractures Need a CT?

BACKGROUND: For rotational ankle fractures with a posterior malleolus fracture (PMF), the decision to further evaluate the ankle injury with computed tomography (CT) is challenging. The objective of this study is to determine how well PMF fracture size on x-rays correlates with size on CT, and how well x-rays can predict which patients receive PMF fixation after CT review. METHODS: This is a retrospective study of adult ankle fractures with PMFs that had preoperative radiographs and CT imaging over a 5-year period. PMF x-ray and CT measurements were recorded, and relationships between x-ray measurements and final PMF fixation plan after CT review were evaluated. RESULTS: A total of 98 patients were identified with both x-rays and preoperative CT imaging. Pearson's rank correlation demonstrated a strong relation between PMF width percentage measured on x-ray and CT (r = 0.724). Of the 45 patients with a PMF size under 20% on x-ray, only one patient (with an apparent incarcerated fragment) underwent PMF fixation after review of the CT. CONCLUSIONS: PMF width on lateral x-ray correlates well with CT size and is sensitive for predicting the need for dedicated posterior malleolus based on one institutional practice pattern. Below 20% fracture width on lateral x-ray, a dedicated CT rarely leads to a decision to perform PMF fixation. Limiting pre-operative CT to those with PMF width >20% could reduce CT utilization by as much as 45% without negatively affecting patient care. LEVELS OF EVIDENCE: Level III: Diagnostic.

What Is the Rate of Displacement of Occult Posterior Malleolus Fractures in Nailed Tibial Shaft Fractures?

OBJECTIVE: To describe the radiographic consequences of posterior malleolus fractures (PMF) present with tibial shaft fractures fixed with intramedullary nails. DESIGN: Retrospective cohort study. SETTING: Level 1 trauma center. PATIENTS/PARTICIPANTS: Seven hundred thirty-three patients with tibial shaft fractures. INTERVENTION: Intramedullary nail fixation and prophylactic articular fixation. MAIN OUTCOME MEASURE: Displacement of PMF with intramedullary nail insertion. RESULTS: Seven hundred thirty-three patients were identified with tibial shaft fractures treated with intramedullary nail fixation at a Level 1 trauma center without a uniform preoperative computed tomography protocol. One hundred thirty-three patients had an identifiable PMF appreciated on preoperative imaging. Of the 600 remaining patients without a known PMF, 29 had PMF identified after nail insertion: 24 patients with nondisplaced fractures that all healed radiographically at final follow-up, 3 patients had fractures <30% of the articular surface displaced 1-2 mm, and 2 patients had fractures >30% of the joint surface that displaced 1-2 mm. CONCLUSIONS: The incidence of radiographically observable PMF associated with tibial shaft fractures is high, even without a preoperative computed tomography screening protocol in place. In patients without an appreciable PMF on injury films, less than 1% (2/600) had displacement of a large, clinically significant PMF with nail placement. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.