Sonography of the coracohumeral interval: a potential technique for diagnosing coracoid impingement

Coracoid impingement has been recognized as an etiology for anterior shoulder pain; however, no imaging reference standard exists. We used sonography to compare the coracohumeral interval (CHI) in asymptomatic volunteers with the CHI in patients with coracoid impingement.

Bilateral shoulder sonography was performed in 19 asymptomatic volunteers (10 men and 9 women) and in 8 shoulders in 7 patients (6 men and 1 woman) with a clinical diagnosis of coracoid impingement. With the arm adducted across the chest, the interval between the coracoid process and the lesser tuberosity of the humerus was measured using a linear array ultrasound transducer with a peak frequency of 13 MHz.

In the asymptomatic volunteers, the mean +/- SD for the CHI was 12.2 +/- 2.5 mm (range, 7.8-17.5 mm). In the symptomatic shoulders, the mean +/- SD for the CHI was 7.9 +/- 1.4 mm (range, 5.9-9.6 mm). Repeated measures analysis of variance revealed the CHI to be significantly narrower in symptomatic shoulders than in asymptomatic volunteers (P < .0001).

These data suggest a role for sonography in diagnosing coracoid impingement.