Predicting Nonunions in Ankle Fractures Using Quantitative Tibial Hounsfield Samples From Preoperative Computed Tomography: A Multicenter Matched Case Control Study.

The aim of this study is to use tibial Hounsfield unit measurements from preoperative computed tomography scans of ankle fractures to predict delayed union and nonunion. We hypothesize that patients with lower Hounsfield unit averages, an indirect measure of lower bone mineral density, in the distal tibia are more likely to develop delayed union and nonunion complications after ankle fracture surgery. Patient data from January 2010 to January 2020 were retrospectively analyzed from 2 institutions. Exposure cases of delayed union or nonunion that had preoperative computed tomography were compared to 5 controls matched for sex, age, and classification. 3 measurements were taken from the tibia on axial computed tomography and averaged to create a summative measure for overall bone health. Statistical analysis was used to analyze the relationship between the groups. 19 exposure patients were compared to 95 control patients. There were 16 females and 3 males in the exposure group aged from 30 to 88 years. Average follow-up was 1.6 years. The average exposure and control Hounsfield measurements were 186 (161-210) and 258 (248-269), respectively. Significant differences were found for all measured averages. This is the first study to our knowledge relating preoperative tibial Hounsfield measurements to healing rates of ankle fractures. Measurements taken from any of the 3 sites or the average could be an indicator of overall bone health. Using this technique on preoperative imaging will help surgeons adjust their perioperative planning for patients at higher risk for delayed union and nonunion.