title: Novel mechano-acoustic technique and instrument for diagnosis of cartilage degeneration.
abstract: Fibrillation of articular surface and depletion of proteoglycans are the structural changes related to early osteoarthrosis. These changes make cartilage softer and prone to further degeneration. The aim of the present study was to combine mechanical and acoustic measurements towards quantitative arthroscopic evaluation of cartilage quality. The performance of the novel ultrasound indentation instrument was tested with elastomers and bovine articular cartilage in vitro. The instrument was capable of measuring elastomer thickness (r = 1.000, p < 0.01, n = 8) and dynamic modulus (r = 0.994, p < 0.01, n = 13) reliably. Osteochondral plugs were tested before and after enzymatic degradation of cartilage proteoglycans by trypsin or chondroitinase ABC, and of cartilage collagens by collagenase. Trypsin and collagenase induced a mean decrease of -31.2 +/- 12.3% (+/- SD, p < 0.05) and -22.9 +/- 20.8% (p = 0.08) in dynamic modulus, respectively. Rate of cartilage deformation, i.e. creep rate, increased by +117.8 +/- 71.4% (p < 0.05) and +24.7 +/- 35.1% (p = 0.17) in trypsin and chondroitinase ABC treatments, respectively. Collagenase induced a greater decrease in the ultrasound reflection from the cartilage surface (-54.2 +/- 29.6%, p < 0.05) than trypsin (-17.1 +/- 13.5%, p = 0.08). In conclusion, combined quantitation of tissue modulus, viscoelasticity and ultrasound reflection from the cartilage surface provides a sensitive method to distinguish between normal and degenerated cartilage, and even to discern proteoglycan loss and collagen degradation from each other.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, University of Kuopio, Finland. mikko.laasanen@uku.fi
authors.forename: M S
authors.initials: MS
authors.lastname: Laasanen
authors.forename: J
authors.initials: J
authors.lastname: Töyräs
authors.forename: J
authors.initials: J
authors.lastname: Hirvonen
authors.forename: S
authors.initials: S
authors.lastname: Saarakkala
authors.forename: R K
authors.initials: RK
authors.lastname: Korhonen
authors.forename: M T
authors.initials: MT
authors.lastname: Nieminen
authors.forename: I
authors.initials: I
authors.lastname: Kiviranta
authors.forename: J S
authors.initials: JS
authors.lastname: Jurvelin
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002357:Cartilage Diseases / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D002417:Cattle; D020724:Elastomers; D008297:Male; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods
chemical_list: D020724:Elastomers