LAUSR

BACKGROUND Elbow fracture dislocations are complex injuries which often require surgical treatment in order to obtain a stable and congruent elbow joint. The coronoid plays a key role in the stability of this joint. Accurately identifying the degree of coronoid bone loss in the setting of traumatic elbow injuries is challenging. The purpose of this study is to describe a new radiographic measure, the Coronoid Opening Angle (COA), to assist in estimating bone loss in these challenging fractures. METHODS Radiographs were drawn from a regional database in a consecutive fashion. Candidate radiographs were excluded on the basis of radiographic evidence of degenerative changes, previous surgery or injury, bony deformity, and inadequate lateral view of the elbow. Normal COA, coronoid height, and calculated COA at varying amounts of bone loss were determined by three reviewers. RESULTS 120 subjects were included. The normal Coronoid Opening Angle is 34 degrees [95% CI: 32.9-34.0]. Coronoid height is 18.8 mm [18.1 - 19.6]. 95% of the population have an opening angle greater than 29 degrees [95% CI: 27.2-29]. The COA limit was calculated at 20%, 33%, and 50% of baseline coronoid height corresponding to degree of bone loss. A Coronoid Opening Angle of 24, 20, and 16 degrees respectively, indicate the minimum bone loss of interest in 95% of the population. ICC was found to be 0.89 or higher. CONCLUSION In the setting of elbow trauma, it is often challenging to predict the amount of coronoid bone loss. The Coronoid Opening Angle is a new technique, and adjunct for lateral elbow radiographs to predict the minimum coronoid bone loss. This can be used to guide clinical decision making, aid to predict instability, and guide treatment. Future research will aim to validate this tool in the clinical trauma setting.