• Daniel A Portney, Manoj Reddy, Hayden P Baker, Daryl B Dillman, Douglas R Dirschl, and Jason A Strelzow.
• Department of Orthopaedic Surgery, The University of Chicago, Chicago, IL.
• J Orthop Trauma. 2021 Jul 1; 35 (7): 361-365.

ObjectivesTo compare the relative frequencies of intra-articular extension of supracondylar distal femur fractures in blunt versus ballistic trauma and the diagnostic accuracy of conventional radiography in identifying intra-articular extension in these fractures.DesignA retrospective review.SettingUrban academic trauma center.Study GroupThirty-eight patients were included for analysis, with 19 blunt and 19 ballistic mechanism distal femur fractures.InterventionFleiss' kappa score was calculated in determining interobserver reliability of the OTA/AO classification. Radiographic specificity and sensitivity were compared using Fischer exact testing. Quantitative data were compared using 2-tailed t-testing for continuous variables and chi-square tests for proportions.Main Outcome MeasurementsRate of intra-articular extension of ballistic versus blunt supracondylar femur fractures.ResultsSeventeen of 19 patients (89.5%) with blunt trauma had intra-articular involvement compared with 5 of 19 patients (26.3%) with ballistic trauma (P = 0.001). For blunt fractures, preoperative radiographs were 94% sensitive for the detection of intra-articular extension compared with 100% sensitive for ballistic fractures (P = 1.000). We identified one case, in the blunt cohort, where the operative plan changed from intramedullary nail to open reduction and internal fixation as a result of the additional coronal plane fracture pattern identified on CT. There were no such occurrences in the ballistic cohort.ConclusionsThe rate of intra-articular extension for ballistic supracondylar femur fractures is lower than blunt distal femur fracture. There were low rates of missed intra-articular fractures and changes in operative plans after reviewing CT imaging for both blunt and ballistic distal femur fractures.Level Of EvidencePrognostic Level III. See Instructions for Authors for a complete description of levels of evidence.Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.

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