Evaluation of cartilage defects with near-infrared spectroscopy (NIR): An ex vivo study

Spahn, Gunter; Plettenberg, Holger; Nagel, Horst; Kahl, Enrico; Klinger, Hans Michael; Mückley, Thomas; Günther, Manfred; Hofmann, Gunther O.; Mollenhauer, Jürgen A.

doi:10.1016/j.medengphy.2007.04.009

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Volume 30, Issue 3 , Pages 285-292, April 2008

Evaluation of cartilage defects with near-infrared spectroscopy (NIR): An ex vivo study

Gunter Spahn
- Center of Traumatology and Orthopeadic Surgery, Eisenach Sophienstr. 16, D-99817 Eisenach, Germany
- Corresponding author.
Holger Plettenberg
- fzmb, Research Center of Medical Technology and Biotechnology, Bad Langensalza, Germany
Horst Nagel
- Research Laboratories, Sartorius AG, Göttingen, Germany
Enrico Kahl
- Orthopaedic Clinic, Georg August University, Göttingen, Germany
Hans Michael Klinger
- Orthopaedic Clinic, Georg August University, Göttingen, Germany
Thomas Mückley
- Department of Trauma, Friedrich Schiller University of Jena, Germany
Manfred Günther
- fzmb, Research Center of Medical Technology and Biotechnology, Bad Langensalza, Germany
Gunther O. Hofmann
- Department of Trauma, Friedrich Schiller University of Jena, Germany
- Trauma Center, Bergamannstrost, Halle, Germany
Jürgen A. Mollenhauer
- Waldkrankenhaus Rudolf Elle Eisenberg with Department of Orthopaedics, Friedrich Schiller University of Jena, Germany

Received 22 February 2007; received in revised form 16 April 2007; accepted 24 April 2007. published online 06 June 2007.

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 1100–1700nm). 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.

Keywords: Cartilage, Defects, NIR, Spectroscopy, Water, Stiffness