title: Ultrasound indentation of normal and spontaneously degenerated bovine articular cartilage.
abstract: OBJECTIVE
  We have previously developed a handheld ultrasound indentation instrument for the diagnosis of cartilage degeneration. The instrument has been demonstrated to be capable of quantifying mechanical and acoustic properties of enzymatically degraded and normal bovine articular cartilage in vitro and in situ. The aim of this study was to investigate the sensitivity of the instrument to distinguish between normal and spontaneously degenerated (e.g., in osteoarthrosis) articular cartilage in vitro.
  
  
  METHODS
  Thirty articular cartilage samples were prepared from the bovine lateral patellae: 19 patellae with different degenerative stages and 11 patellae with visually normal appearance. Cartilage thickness, stiffness (dynamic modulus) and ultrasound reflection from the cartilage surface were measured with the handheld instrument. Subsequently, biomechanical, histological and biochemical reference measurements were conducted.
  
  
  RESULTS
  Reproducibility of the measurements with the ultrasound indentation instrument was good. Standardized coefficient of variation was < or =6.1% for thickness, dynamic modulus and reflection coefficient. Linear correlation between the dynamic modulus, measured with the ultrasound indentation instrument, and the reference dynamic modulus was high (r=0.993, n=30, P<0.05). Ultrasound reflection coefficient, as determined from the cartilage surface, showed high linear correlations (typically r(2)>0.64, n=30, P<0.05) with the cartilage composition and histological or mechanical properties. The instrument was superior compared to visual evaluation in detecting tissue degeneration.
  
  
  CONCLUSIONS
  This study indicates that the ultrasound indentation technique and instrument may significantly improve the early diagnosis of cartilage degeneration. The results revealed that visual evaluation is insensitive for estimating the structural and mechanical properties of articular cartilage at the initial stages of degeneration.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital and University of Kuopio, POB 1777, 70211 Kuopio, Finland. saarakka@hytti.uku.fi
authors.forename: S
authors.initials: S
authors.lastname: Saarakkala
authors.forename: M S
authors.initials: MS
authors.lastname: Laasanen
authors.forename: J S
authors.initials: JS
authors.lastname: Jurvelin
authors.forename: K
authors.initials: K
authors.lastname: Törrönen
authors.forename: M J
authors.initials: MJ
authors.lastname: Lammi
authors.forename: R
authors.initials: R
authors.lastname: Lappalainen
authors.forename: J
authors.initials: J
authors.lastname: Töyräs
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D002417:Cattle; D010003:Osteoarthritis / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D010329:Patella / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D014463:Ultrasonography