Ultrasound evaluation of the acromioclavicular joint -: A correlation of anatomical and sonographical findings

Aim: To compare ultrasound imaging to the anatomy of the acromioclavicular joint. Methods: 13 cadaveric acromioclavicular joints were examined by ultrasound (11 MHz linear array transducer) to determine the limits of the joint capsule and the width of the joint space. The results were compared to macroscopic sections. Results: Anatomical variations were observed. The joint space of one specimen was completely filled by fibrous tissue, leaving 12 specimens for a complete study. A hypoechoic meniscoid disc was attached to the superior joint capsule, resulting in a convex curvature of the cranial part. The mean sonographic width of the joint space was 3.9 mm +/- 1.7 mm standard deviation (SD). The mean distance of the joint capsule from the articular bone rim of the clavicle, the acromion, and from the middle of the joint space was 1.1 +/- 1.0 mm, 1.3 +/- 0.7 mm, and 2.1 +/- 0.9 mm, respectively. The distance from the joint space to the capsular insertion on the clavicle and on the acromion was 4.4 +/- 1.4 mm and 5.3 +/- 2 mm, respectively. The mean difference between ultrasound and anatomical measurements in the vertical (cranio-caudal) plane was 0.5 +/- 0.5 mm (SD), whereas the mean difference between measurements in the horinzontal (medio-lateral) plane was 1.3 +/- 1.1 mm (SD). Conclusion: Due to low cost, safety and wide availability, sonography is suited for the evaluation of the acromioclavicular joint. However, when interpreting the results, errors in measuring, limitations in resolution of the system used, and the anatomy of the acromioclavicular joint and its anatomical variants have to be taken into consideration.