J. Toyras et al., Characterization of enzymatically induced degradation of articular cartilage using high frequency ultrasound, PHYS MED BI, 44(11), 1999, pp. 2723-2733
Ultrasound may provide a quantitative technique for the characterization of
cartilage changes typical of early osteoarthrosis. In this study, specific
changes in bovine articular cartilage were induced using collagenase and c
hondroitinase ABC, enzymes that selectively degrade collagen fibril network
and digest proteoglycans, respectively. Changes in cartilage structure and
properties were quantified using high frequency ultrasound, microscopic an
alyses and mechanical indentation tests. The ultrasound reflection coeffici
ent of the physiological saline-cartilage interface (R-1) decreased signifi
cantly (-96.4%, p < 0.01) in the collagenase digested cartilage compared to
controls. Also a significantly lower ultrasound velocity (-6.2%, p < 0.01)
was revealed after collagenase digestion. After chondroitinase ABC digesti
on, a new acoustic interface at the depth of the enzyme penetration front w
as detected. Cartilage thickness, as determined with ultrasound, showed a h
igh, linear correlation (R = 0.943, n = 60, average difference 0.073 mm (4.
0%)) with the thickness measured by the needle-probe method. Both enzymes i
nduced a significant decrease in the Young's modulus of cartilage (p < 0.01
). Our results indicate that high frequency ultrasound provides a sensitive
technique for the analysis of cartilage structure and properties. Possibly
ultrasound may be utilized in vivo as a quantitative probe during arthrosc
opy.