Using the radiocoronoid line for diagnosis of elbow dislocation

Abstract

The radiocapitellar line (RCL) has been widely used to diagnose elbow dislocation. However, there are limitations to the RCL, with the cartilaginous portion of bone making interpretation of radiographs difficult. The study aims to show that the radiocoronoid line, which connects two points on the medial aspect of the radius, proximal to the radial tuberosity, is more suited to diagnose elbow dislocations in the anterior-posterior projection. This study also observes factors affecting accuracy of the radiocapitellar line. The radiographs of 50 normal and 17 laterally dislocated elbows were obtained. An unbiased independent reviewer drew the radiocoronoid and radiocapitellar line (RCL). Four other blinded independent reviewers drew the RCL and the radiocoronoid line for 20 radiographs and repeated the process a week later. The accuracy of the RCL was assessed using distance away from bisection point of capitellum, and ratio (distance from the point where line crosses capitellum to lateral aspect of capitellum over the total width of capitellum). The relationship of the radio-coronoid line and the lateral aspect of coronoid fossa was assessed, with dislocation being the line lateral to it and normal being medial to or on it. The radiocoronoid line had a higher accuracy (95.5%) compared to RCL (32.8%), higher specificity (94%) compared to RCL (10%) as well as higher positive predictive value (85%) compared to RCL (27.4%). There was no intra- or inter-observer variability for the radio-coronoid line. Skeletal age statistically predicted the ratio for the male population ( P < 0.05), however, the independent variables did not statistically predict the dependent variables for the female and total population. The radiocoronoid line serves as an additional method to assess radiocapitellar joint lateral dislocation. It is more accurate and reliable than the radiocapitellar line in the anterior-posterior projection. Sex and skeletal age also influence the accuracy of the radiocapitellar line with the radiocapitellar line nearing the bisection point as skeletal age in males increases.