Ultrasound of the coracoacromial ligament in asymptomatic volunteers and patients with shoulder impingement.
BACKGROUND
The coracoacromial ligament is part of the coracoacromial arch, which is considered to be involved in shoulder impingement.


OBJECTIVE
To compare the coracoacromial ligament on ultrasound in asymptomatic volunteers and in patients with subacromial shoulder impingement.


METHODS
Twenty-nine asymptomatic volunteers (mean age, 35.5 years) and 29 patients (mean age, 49.9 years) with shoulder impingement, diagnosed by experienced shoulder surgeons, were prospectively included. Two radiologists obtained and analyzed ultrasound images of the coracoacromial ligament in the longitudinal axis.


RESULTS
The ligament thickness was 1.4 ± 0.2 mm at its midportion, 1.8 ± 0.4 mm at the coracoid, and 2.1 ± 0.6 mm at the acromion in asymptomatic volunteers compared with 1.3 ± 0.2 mm, 1.9 ± 0.5 mm, and 1.9 ± 0.5 mm in impingement patients for observer 1. The ligament length was 30.6 ± 2.4 mm in asymptomatic volunteers compared with 30.4 ± 3.6 mm in impingement patients for observer 1. An anteriorly convex shape of the superficial contour of the coracoacromial ligament was significantly more frequent in impingement patients compared with asymptomatic volunteers for both observers (observer 1: 10% (3/29) versus 45% (13/29), P value <0.01; observer 2: 10% (3/29) versus 38% (11/29), P value <0.03). The comparison of the remaining parameters of the coracoacromial ligament, such as the thickness, length, echogenicity, and fibrillation did not reveal significant differences between volunteers and patients.


CONCLUSIONS
While thickness or length of the coracoacromial ligament were similar in volunteers and patients with shoulder impingement, an anteriorly convex shape of the superficial contour of the coracoacromial ligament was significantly more frequent in impingement patients compared with asymptomatic volunteers.
Radiology, Orthopedic University Hospital Balgrist, Faculty of Medicine, University of Zurich, Zurich, Switzerland tobiasjdietrich@gmail.com.
Tobias J
TJ
Dietrich
Radiology, Orthopedic University Hospital Balgrist, Faculty of Medicine, University of Zurich, Zurich, Switzerland.
Maciej
M
Jonczy
Radiology, Orthopedic University Hospital Balgrist, Faculty of Medicine, University of Zurich, Zurich, Switzerland.
Florian M
FM
Buck
Radiology, Orthopedic University Hospital Balgrist, Faculty of Medicine, University of Zurich, Zurich, Switzerland.
Reto
R
Sutter
Orthopedic Surgery, Orthopedic University Hospital Balgrist, Faculty of Medicine, University of Zurich, Zurich, Switzerland.
Gabor J
GJ
Puskas
Radiology, Orthopedic University Hospital Balgrist, Faculty of Medicine, University of Zurich, Zurich, Switzerland.
Christian Wa
CW
Pfirrmann
D000173:Acromioclavicular Joint / Q000000981:diagnostic imaging* / Q000502:physiology / Q000503:physiopathology; D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008023:Ligaments, Articular / Q000000981:diagnostic imaging* / Q000502:physiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019534:Shoulder Impingement Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014463:Ultrasonography / Q000379:methods*
Ultrasound; coracoacromial ligament; shoulder impingement syndrome; volunteers