Table 1 Histological grading system^a

   4 = Mostly hyaline cartilage

   1 = <25% of the calcified cartilage layer intact

   1 = Not bonded

   3 = Mostly fibrocartilage

   2 = 25-49% of the calcified cartilage layer intact

   2 = Bonded at one end/partially both ends

   2 = Mostly noncartilage

   3 = 50-75% of the calcified cartilage layer intact

   3 = Bonded at both sides

   1 = Exclusively noncartilage

   4 = 76-90% of the calcified cartilage layer intact

Basal integration of implanted material (Basl)

Matrix staining (Matx)

   5 = Complete intactness of the calcified cartilage layer

   1 = <50%

   1 = None

Subchondral bone formation (Bform)

   2 = 50-70%

   2 = Slight

   1 = No formation

   3 = 70-90%

   3 = Moderate

   2 = Slight

   4 = 91-100%

   4 = Strong

   3 = Strong

Inflammation (InfH)

Structural integrity (Stru)

Histologic appraisal of surface architecture (SurfH)

   1 = Strong inflammation

   1 = Severe disintegration

   1 = Severe fibrillation

   3 = Slight inflammation

   2 = Cysts or disruption

   2 = Moderate fibrillation

   5 = No inflammation

   3 = No organization of chondrocytes

   3 = Slight fibrillation or irregularity

Histologic grading system (Hgtot)

   4 = Beginning of columnar organization of chondrocytes

   4 = Normal

   Some of the histologic variables:

   5 = Normal, similar to healthy mature cartilage

Histologic appraisal defect filling (FilH)

   Tissue morphology (Ti)

Chondrocytes clustering in implant (Clus)

   1 = <25%

   Matrix staining (Matx)

   1 = 25-100% of cells clustered

   2 = 26-50%

   Structural integrity (Stru)

   2 = <25% of the cells clustered

   3 = 51-75%

   Cluster formation (Clus)

   3 = No clusters

   4 = 76-90%

   Tidemark opening (Tide)

   5 = 91-110%

   Bone formation (Bform)

   Histologic surface architecture (SurfH)

   Histologic degree of defect filling (FilH)

   Lateral integration of defect-filling tissue (Basl) and histologic signs of inflammation (InfH)