Degenerated coracoacromial ligament in shoulders with rotator cuff tears shows higher elastic modulus: measurement with scanning acoustic microscopy.
OBJECTIVE
The purpose of this study was to determine the elasticity of the coracoacromial ligament in shoulders with and without rotator cuff tears.


METHODS
The coracoacromial ligaments from 20 cadaveric shoulders (average patient age 79.5 years; 8 men, 12 women) were divided into six portions--three portions (acromial, central, and coracoid) in two layers (superficial and deep). A total of 120 samples were studied. First, the samples were classified by the collagen fiber orientation into three degeneration patterns: wavy, straight, irregular. For each pattern, the tissue sound speed, which shows a positive correlation with elasticity, was measured with scanning acoustic microscopy. Next, the samples were divided into three groups: 60 samples from shoulders with rotator cuff tears (RCT group), 30 samples from shoulders with an intact rotator cuff and a subacromial spur (spur group), and 30 samples from shoulders with an intact rotator cuff without a subacromial spur (control group). All shoulders with rotator cuff tears had subacromial spurs. The tissue sound speed and the histological findings were compared among the groups.


RESULTS
The sound speeds in the wavy, straight, and irregular patterns were 1592 +/- 17.2 m/s (mean +/- SD), 1626 +/- 28.0 m/s, and 1607 +/- 29.8 m/s, respectively (P < 0.0001). The sound speed in the straight pattern was higher than that in the wavy pattern (P < 0.0001), and that in the irregular pattern was lower than that in the straight pattern (P = 0.0023). The RCT group and the spur group had more straight patterns (P = 0.0002) and fewer wavy patterns (P < 0.0001) than did the control group. Significant differences in the sound speed were observed between the groups (P < 0.0001): 1596 +/- 19.1 m/s in the control group, 1630 +/- 31.5 m/s in the spur group, 1612 +/- 28.6 m/s in the RCT group.


CONCLUSIONS
The coracoacromial ligament in shoulders with rotator cuff tears shows higher elastic modulus than in age-matched normal shoulders due to degeneration of the ligament.
Kijima
Hiroaki
H
Division of Orthopedic Surgery, Department of Neuro and Locomotor Science, Akita University School of Medicine, 1-1-1 Hondo, Akita, 010-8543, Japan.
Minagawa
Hiroshi
H
Saijo
Yoshifumi
Y
Sano
Hirotaka
H
Tomioka
Tatsuru
T
Yamamoto
Nobuyuki
N
Shimada
Yoichi
Y
Okada
Kyoji
K
Itoi
Eiji
E
D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008023:Ligaments, Articular / Q000033:anatomy & histology* / Q000473:pathology*; D008297:Male; D033401:Microscopy, Acoustic; D008875:Middle Aged; D017006:Rotator Cuff / Q000033:anatomy & histology* / Q000473:pathology*; D000070636:Rotator Cuff Injuries