title: Evaluation of cartilage defects with near-infrared spectroscopy (NIR): an ex vivo study.
abstract: Damaged cartilage undergoes complex changes in composition, histological structure, and mechanical properties. Near-infrared-spectroscopy (NIR spectroscopy) is an important method to measure changes in composition of complex composites. The present study was aimed at evaluating NIR spectroscopy as a means to quantitate tissue alterations in low grade cartilage defects. Fresh medial femoral condyles from female sheep were collected. Cartilage defects were graded according to the International Cartilage Repair Society (ICRS). Specimens were examined by a NIR spectroscopy device (spectral range of 1100-1700 nm). Absorption spectra were calculated from the reference and measurement spectra. As indicator for cartilage composition the ratio (absorption ratio, AR) of the two main absorption bands in this region was calculated. Mechanical stiffness was measured as Shore A. Water-, glycosaminoglycan-, and collagen content and histological grade (Mankin score) were determined. The NIR absorption in ICRS grade 1 defects (AR=2.1+/-0.1) was significantly higher than in intact cartilage (AR=1.5+/-0.1). ICRS grade 2 specimens tended to a higher NIR absorption. NIR absorption correlated significantly with Mankin score (R=0.896), water content (R=0.845), and mechanical stiffness (R=0.877). Initial cartilage degeneration correlates with changes in NIR absorption, indicating NIR spectroscopy to reflect complex structural changes in degenerated cartilage. The data suggest that NIR spectroscopy could be useful for in situ detection of early cartilage defects.
authors.affiliation: Center of Traumatology and Orthopaedic Surgery, Eisenach Sophienstrasse 16, Eisenach, Germany. spahn@pk-eisenach.de
authors.forename: Gunter
authors.initials: G
authors.lastname: Spahn
authors.forename: Holger
authors.initials: H
authors.lastname: Plettenberg
authors.forename: Horst
authors.initials: H
authors.lastname: Nagel
authors.forename: Enrico
authors.initials: E
authors.lastname: Kahl
authors.forename: Hans Michael
authors.initials: HM
authors.lastname: Klinger
authors.forename: Thomas
authors.initials: T
authors.lastname: Mückley
authors.forename: Manfred
authors.initials: M
authors.lastname: Günther
authors.forename: Gunther O
authors.initials: GO
authors.lastname: Hofmann
authors.forename: Jürgen A
authors.initials: JA
authors.lastname: Mollenhauer
mesh_terms: D000818:Animals; D002356:Cartilage / Q000473:pathology*; D002357:Cartilage Diseases / Q000175:diagnosis*; D003094:Collagen / Q000032:analysis; D019245:Compressive Strength; D004548:Elasticity; D005260:Female; D006025:Glycosaminoglycans / Q000032:analysis; D066298:In Vitro Techniques; D007259:Infrared Rays; D012016:Reference Values; D012756:Sheep; D019265:Spectroscopy, Near-Infrared; D014867:Water / Q000032:analysis
chemical_list: D006025:Glycosaminoglycans; D014867:Water; D003094:Collagen