Accuracy of the sonographic acromion to greater tuberosity distance during abduction in the diagnosis of shoulder impingement syndrome

Abstract

Shoulder impingement is the painful entrapment of the soft tissues in the shoulder outlet. Currently, dynamic sonography of the shoulder is the modality of choice for the evaluation of shoulder impingement syndrome. However, the current sonographic criteria for the evaluation of shoulder impingement is more subjective (operator dependent). And it is rather difficult for a novice observer to diagnose it. The measurable distance between acromion and greater tuberosity is during shoulder abduction is considered for shoulder impingement syndrome. Objective: To estimate the accuracy of the acromion to greater tuberosity distance in shoulder abduction as a sonographic diagnostic parameter for the shoulder impingement syndrome. Methods: Seven hundred and seventy-two shoulders were observed in this study. All the shoulders were evaluated with Toshiba Xario Prime ultrasound Unit with linear transducer 7-14MHz. Acromion to greater tuberosity distance was measured during the abducted arm. All the shoulders with measurable distance during abduction were declared as positive for impingement while unmeasurable distance due to disappearance of the greater tuberosity underneath the acromion was normal. Results: At 95% confidence interval, the sensitivity, and specificity with lower and upper limits, of the acromion to greater tuberosity distance during abduction for the diagnosis of shoulder impingement syndrome were 0.9731% (95.25 to 98.49%) and 100% (98.49 to 100%) respectively. While the positive-predictive and negative-predictive value were 100% (98.22% to 100%) and 97.12% (94.96% to 98.37%) respectively. However, the overall Accuracy at 95% confidence interval was 98.45% (97.30% to 99.20%). There was a high-grade interobserver (novice and expert) agreement in the diagnosis of shoulder impingement through this criteria with a Kappa value of 0.96. Conclusion: Sonographically measurable acromion to greater tuberosity distance in abduction is a more accurate, reliable, and objective technique for the diagnosis of shoulder impingement syndrome.