title: Optical coherence tomography detection of subclinical traumatic cartilage injury.
abstract: OBJECTIVE
  Posttraumatic arthritis is a major cause of disability. Current clinical imaging modalities are unable to reliably evaluate articular cartilage damage before surface breakdown, when potentially reversible changes are occurring. Optical coherence tomography (OCT) is a nondestructive imaging technology that can detect degenerative changes in articular cartilage with an intact surface. This study tests the hypothesis that OCT detects acute articular cartilage injury after impact at energy levels resulting in chondrocyte death and microstructural changes, but insufficient to produce macroscopic surface damage.
  
  
  METHODS
  Bovine osteochondral cores underwent OCT imaging and were divided into a control with no impact or were subjected to low (0.175 J) or moderate (0.35 J) energy impact. Cores were reimaged with OCT after impact and the OCT signal intensity quantified. A ratio of the superficial to deep layer intensities was calculated and compared before and after impact. Chondrocyte viability was determined 1 day after impact followed by histology and polarized microscopy.
  
  
  RESULTS
  Macroscopic changes to the articular surface were not observed after low and moderate impact. The OCT signal intensity ratio demonstrated a 27% increase (P = 0.006) after low impact and a 38% increase (P = 0.001) after moderate impact. Cell death increased by 150% (P < 0.001) and 200% (P < 0.001) after low and moderate energy impacts, respectively. When compared with unimpacted controls, both Mankin histology and David-Vaudey polarized microscopy scores increased (P = 0.036 and P = 0.002, respectively) after moderate energy impact.
  
  
  CONCLUSIONS
  This study shows that OCT detects acute cartilage changes after impact injury at levels insufficient to cause visible damage to the articular surface but sufficient to cause chondrocyte death and microscopic matrix damage. This finding supports the use of OCT to detect microstructural subsurface cartilage damage that is poorly visualized with conventional imaging.
authors.affiliation: Cartilage Restoration Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Bear
authors.forename: Michal
authors.initials: M
authors.lastname: Szczodry
authors.forename: Scott
authors.initials: S
authors.lastname: Kramer
authors.forename: Christian H
authors.initials: CH
authors.lastname: Coyle
authors.forename: Patrick
authors.initials: P
authors.lastname: Smolinski
authors.forename: Constance R
authors.initials: CR
authors.lastname: Chu
mesh_terms: D000818:Animals; D017209:Apoptosis; D002358:Cartilage, Articular / Q000473:pathology*; D002417:Cattle; D002470:Cell Survival; D019902:Chondrocytes / Q000473:pathology*; D005109:Extracellular Matrix / Q000473:pathology; D050724:Fractures, Cartilage / Q000175:diagnosis*; D008856:Microscopy, Fluorescence; D041623:Tomography, Optical Coherence / Q000379:methods*; D014947:Wounds and Injuries / Q000473:pathology*