Ultrasound evaluation of the acromioclavicular joint. A comparison with magnetic resonance imaging

Ultrasound is useful in detecting acromioclavicular pathologies in cases of trauma, inflammations and degenerative changes in sports medicine. Many studies compare joint space and capsular dimensions of symptomatic and asymptomatic patients. However, no study has examined the reproducibility and reliability of these measurements. The aim of this study was to evaluate the reliability of ultrasonographic measurements in assessing the acromioclavicular joint. 27 acromioclavicular joints of 15 healthy subjects were examined by T1 weighted magnetic resonance imaging (MRI) to determine the normal limits of joint space (a) and joint capsule (b). These measurements were compared to standardised ultrasonographic (11 Mhz) measurements, which were repeated three times. The mean difference between MRI and ultrasound measurements was 1.5 +/- 1.3 mm and 1.3 +/- 1.2 mm for distance a and b, respectively. Reproducibility of ultrasonographic measurements was high with a mean standard deviation of 0.3 +/- 0.2 mm and 0.4 +/- 0.3 mm for distance a and b, respectively. Due to low costs, safety and wide availability ultrasonography is suited for the evaluation of the acromiocalvicular joint. However, when interpreting the results measurement errors, limitations in resolution of the system used, and the anatomy of the acromioclavicular joint and its anatomic variants have to be taken into consideration.