Four-part proximal humeral fractures: diagnosis with the 'sunset' sign on anteroposterior radiograph.

INTRODUCTION: Four-part proximal humeral fractures require surgical intervention. However, they can be difficult to diagnose in radiological images. We aim to define a new, easily recognisable, radiological sign as a predictor of four-part fracture of the proximal humerus in a plain anteroposterior radiograph of the shoulder. PATIENTS AND METHODS: We describe our 'sunset' sign as 'articular surface of humeral head pointing away from the glenoid and tilted upwards, in the presence of a displaced greater tuberosity fracture'. We postulate that a patient with proximal humerus fracture showing this sign has four-part fracture until proven otherwise. Between 2002 and 2006, 80 consecutive patients had surgical treatment of their proximal humeral fractures in our unit. Pre-operative radiographs and operative notes of 79 patients were evaluated independently by three blinded observers. The presence of 'sunset' sign was recorded. Findings were then correlated with the operative diagnoses to confirm whether they were four-part fractures or not. With 95% confidence interval, we calculated the sensitivity, specificity, positive and negative predictive values for our diagnostic sign.
RESULTS: Of 79 patients, 30 displayed 'sunset' sign in their pre-operative radiograph. Of these, 28 had confirmed four-part fractures operatively. The positive predictive value of 'sunset' sign was 93%. The specificity and sensitivity were 95% and 78%, respectively. The sensitivity was affected by eight patients with four-part fractures with displaced articular head fragment which had dropped either medially or posteriorly.
CONCLUSIONS: These results suggest that, in patients with proximal humeral fractures, the presence of 'sunset' sign in the anteroposterior radiograph is a reliable indicator of four-part fracture.