title: Indentation probing of human articular cartilage: Effect on chondrocyte viability.
abstract: BACKGROUND
  Clinical arthroscopic probes based on indentation testing are being developed. However, the biological effects of certain design parameters (i.e., tip geometry and size) and loading protocols (i.e., indentation depth, rate, and repetition) on human articular cartilage are unclear.
  
  
  OBJECTIVE
  Determine if indenter design and indentation protocol modulate mechanical injury of probed cartilage samples.
  
  
  METHODS
  The objectives of this study were to determine the effects of indentation testing using clinically applicable tips (0.4mm radius, plane- or sphere-ended) and protocols (indentation depths of 100, 200, or 300 microm, applied at a rate of 50 or 500 microm/s) on the extent and the pattern of chondrocyte death, should it occur. Grossly normal osteochondral blocks were harvested from human talar dome, indented, stained with live/dead dyes, and imaged en face on a fluorescence microscope.
  
  
  RESULTS
  The occurrence and the extent of cell death generally increased with indentation depth, being undetected at an indentation depth of 100 microm but marked at 300 microm. In addition, tip geometry affected the pattern of cell death: ring- and solid circle-shaped areas of cell deaths were apparent when compressed to 300 microm using plane- and sphere-ended indenters.
  
  
  CONCLUSIONS
  Indenter design and indentation protocol modulated the extent and the pattern of chondrocyte death. These results have implications for designing indentation probes and protocols, as well as clinicians performing arthroscopic probing.
authors.affiliation: Department of Bioengineering, University of California-San Diego, La Jolla, CA 92093, USA.
authors.forename: W C
authors.initials: WC
authors.lastname: Bae
authors.forename: B L
authors.initials: BL
authors.lastname: Schumacher
authors.forename: R L
authors.initials: RL
authors.lastname: Sah
mesh_terms: D001182:Arthroscopy / Q000379:methods* / Q000592:standards; D001696:Biomechanical Phenomena / Q000295:instrumentation / Q000379:methods*; D002102:Cadaver; D002358:Cartilage, Articular / Q000473:pathology*; D016923:Cell Death; D019902:Chondrocytes; D004867:Equipment Design; D006801:Humans; D008856:Microscopy, Fluorescence; D013628:Talus / Q000473:pathology