Why the dog?

Analogy of the anatomy

Surgically Induced canine OA models:

• Anterior (cranial) cruciate ligament transection model Pond MJ, Nuki G. Ann Rheum Dis 1973 (and > 100 others)

• Meniscal disruption models o Menisectomy model Lindhorst E, et al. J Orthop Res 2000 (and others)

o Meniscal release model Luther JK, et al. Vet Surg 2009

• Groove model Marijnissen AC, et al. OA Cartilage 2002 (and others)

Arthrotomy vs. Arthroscopy

Outcome Measures – Clinical Relevance

Clinical Canine Patients

Histological/histochemical Grading SystemMankin HJ, et al. 1971 J Bone Joint Surg Am

Category

Subcategory

Scor

e

Structure

Normal

Surface irregularities

Pannus and surface irregularities

Clefts to transitional zone

Clefts to radial zone

Clefts to calcified zone

Complete disorganization

0

1

2

3

4

5

6

Cells

Normal

Diffuse hypercellularity

Cloning

Hypocellularity

0

1

2

3

Proteoglycan staining (Safranin O)

Normal

Slight reduction

Moderate reduction

Severe reduction

No dye noted

0

1

2

3

4

Tidemark integrity

Intact

Crossed by blood vessels

0

1

Total 0 –14

• Inadequate differentiation between mild OA and moderate OA

• Inadequate reproducibility and validity

• Inadequate representation/weight of the relative importance

• Lack of a standardized sampling method

• Lack of global assessment of articularcartilage

• Lack of assessment of the joint as a whole

Ostergaard et al. Ann Rheum Dis 1999

Ostergaard et al. Arthritis Rheum 1997

Grade

(key feature)

Associated criteria

0

(surface intact, cartilage

morphology intact)

Matrix: Normal architecture

Cells: Intact, appropriate orientation

1

(surface intact)

Matrix: Superficial zone intact, edema, and/or superficial fibrillation, focal superficial matrix

condensation

Cells: Death, proliferation (clusters), hypertrophy, superficial zone

2

(surface discontinuity)

As above

+ matrix discontinuity at superficial zone (deep fibrillation)

+/- cationic stain matrix depletion upper 1/3 of cartilage

+/- focal perichondral increased stain (mid zone)

+/- disorientation of chondrone columns

Cells: Death, proliferation (clusters), hypertrophy

3

(vertical fissures/clefts)

As above

+ vertical fissures into mid zone, branched fissures

+/- cationic stain depletion into lower 2/3 of cartilage (deep zone)

+/- new collagen formation

Cells: Death, regeneration (clusters), hypertrophy, cartilage domains adjacent to fissures

4

(erosion)

Cartilage matrix loss: delamination of superficial layer, mid layer cyst formation

Excavation: matrix loss superficial layer and mid zone

5

(denudation)

Surface: sclerotic bone or reparative tissue including fibrocartilage within denuded surface.

Microfracture with repair limited to bone surface.

6

(deformation)

Bone remodelling (more than osteophyte formation only) including microfracture with

fibrocartilaginous and osseous repair extending above the previous surface

OA score = grade x *stage *% area involvement in a tissue section

0: no OA, 1: < 10%, 2: 10 -25%, 3: 25 -50%, 4: >50%

Articular cartilage: Human vs. Dog

Human femoral condyle Canine femoral condyle

Human Canine

Thickness (mm) 2.26 0.67

Cell density (104/mm3) 1.4 4.4

Stockwell RA. J Anat 1971

S

M

D

C

Macroscopic assessment of cartilage

A Smooth surface 0

B Slightly fibrillated/roughened surface 1

C Fibrillated surface with focal partial thickness lesions 2

D Deep lesions with surrounding damage 3

E Large areas of severe damage 4

Macroscopic cartilage scoring for each weight bearing compartment,

based on Outerbridge classification (J Bone Joint Surg Br 1961) and

modified from Masterbergen et al (Rheumatology 2006)

EE

Macroscopic assessment of cartilage

Indian ink staining

% area of cartilage

damage

FEMUR

TIBIA

3 2 11 2 3

1 2 33 2 1

3 2 11 2 3

1 2 33 2 1

Sample collection for histopathology

Scoring SystemCartilage & Osteochondral tissues

Pathological Changes in Each

Category

EXTENT OF SECTION AFFECTED

< 1/3

(Focal)

< 2/3

(Multifocal,

Focally extensive)

>2/3

(Multifocal,

Diffuse )

A Normal 0 0 0

B Less severe pathology 1 2 3

C 2 4 6

D 3 6 9

E Most severe pathology 4 8 12

1/3

DD

C 1/3 of section scored D

+

1/3 of section scored D

+

1/3 of section scored C

= 6 + 2 = 8

Tissue Categories (use one or more)

Articular

cartilage

Cartilage structure

Chondrocytes

Proteoglycan staining intensity

Collagen integrity

Osteochondral

tissue

Tide mark integrity

Subchondral bone changes

Cartilage Pathology: Structural change

SEVERITY OF CARTILAGE PATHOLOGY

Characteristics

EXTENT OF SECTION AFFECTED

< 1/3 < 2/3 >2/3

A Normal volume, smooth surface with intact superficial zone 0 0 0

B Slight surface irregularities including fibrillations/fissures in

superficial zone

1 2 3

C Clefts/fissures to mid zone and/or erosion of superficial zone 2 4 6

D Cleft/fissures that extend to deep zone and/or erosion through

mid zone

3 6 9

E Full thickness loss/deformation of cartilage 4 8 12

Cartilage Pathology: Structural Change – examples

a. Small focal area (<1/3) of fibrillation in

superficial zone = 1

b. Focally extensive area of erosion of

superficial zone (<2/3) = 4

c. Diffuse (>2/3) erosion through mid

zone = 9c

a

SEVERITY OF CARTILAGE PATHOLOGY

Characteristics

EXTENT OF SECTION

AFFECTED

< 1/3 < 2/3 >2/3

A Normal volume, smooth surface with intact superficial zone 0 0 0

B Slight surface irregularities including fibrillations/fissures in superficial zone 1 2 3

C Clefts/fissures to mid zone and/or erosion of superficial zone 2 4 6

D Cleft/fissures that extend to deep zone and/or erosion through mid zone 3 6 9

E Full thickness loss/derangement of cartilage 4 8 12

b

Cartilage Pathology: Chondrocyte change

SEVERITY OF CHONDROCYTE PATHOLOGY

Characteristics

EXTENT OF SECTION

AFFECTED

< 1/3 < 2/3 >2/3

A Normal 0 0 0

BRelative hypocellularity at the articular surface or hypercellularity with

occasional superficial clones1 2 3

C Frequent clones, small cell clones predominate 2 4 6

D Frequent clones, large cell clones predominate 3 6 9

E Cell loss predominates 4 8 12

Normal = 0 Frequent small clones

(duos and trios) = 2

Frequent large cell clones

= 3

A C D

CATIONIC STAINING

(PROTEOGLYCAN)

Characteristics

EXTENT OF SECTION

AFFECTED

< 1/3 < 2/3 >2/3

A Normal 0 0 0

B Reduction of staining in the superficial zone 1 2 3

C Reduction of staining into the mid zone 2 4 6

D Reduction of staining into the deep zone 3 6 9

E Full depth reduction of staining 4 8 12

Cartilage Pathology: Proteoglycan staining

Toluidine blue Safranin O

Cartilage Pathology: Collagen integrity

Collagen type II

Collagen type I

COLLAGEN DERRANGEMENT

Characteristics

EXTENT OF SECTION

AFFECTED

< 1/3 < 2/3 >2/3

A Normal 0 0 0

B Loss of integrity of superficial zone 1 2 3

C Loss of integrity of surface and mid zones 2 4 6

D Loss of integrity of surface, mid and deep zones 3 6 9

Picrosirius red staining with polarized light

AA BB CC

TIDEMARK INTEGRITYEXTENT OF SECTION AFFECTED

< 1/3 < 2/3 >2/3

A Intact and distinct 0 0 0

B Not consistent or distinct (loss and/or duplication) 1 2 3

C Loss of tidemark which is crossed by blood vessels 2 4 6

Osteochondral pathology: Tidemark integrity

A. Apparently normal tidemark = 0 B. Indistinct tidemark = 1

B. Duplication of tidemark = 1 C. Loss of tidemark with vascular

penetration = 2

SUBCHONDRAL BON CHANGES

EXTENT OF SECTION

AFFECTED

< 1/3 < 2/3 >2/3

A Apparently normal thickness 0 0 0

B Mild to moderate increase in thickness 1 2 3

C Marked increase in thickness and/or subchondral pseudocysts 2 4 6

Osteochondral Pathology: Subchondral bone change

A B C

Increased in thickness Subchondral pseudocysts

C

Synovial changes

Scoring system: Synovium

SEVERITY OF PATHOLOGY3 sections of synovium (medial, axial, and

lateral compartments if possible)

Lining cells characteristics

(Synoviocyte changes)Lateral (1/3) Medial (1/3) Axial (1/3)

A Normal (1 to 2 cell layers of thin synoviocytes) 0 0 0

B Hypertrophy and/or mild to moderate hyperplasia 1 2 3

C Marked hyperplasia (> 6 cell layers) 2 4 6

Lining characteristics

(Tissue morphologic changes)

A Normal 0 0 0

B Short villi formation 1 2 3

C Finger-like projections 2 4 6

Cell infiltration characteristics

A No inflammatory cell infiltration 0 0 0

B Mild to moderate inflammatory cell infiltration 1 2 3

C Marked inflammatory cell infiltration, lymphoid proliferation 2 4 6

Lateral

Medial

Axial

Tissue Categories (use one or more)

Synovium Synoviocytes

Tissue morphology

Cellular infiltrates

Synovial Pathology:Lining synoviocytes changes

SEVERITY OF PATHOLOGY

Lining cells characteristics

SECTION

AFFECTED

1/3 1/3 1/3

A Normal (1 to 2 cell layers of thin synoviocytes) 0 0 0

B Hypertrophy and/or mild to moderate hyperplasia 1 2 3

C Marked hyperplasia (>6 cell layers) 2 4 6

AA BB CC

Apparently normal

synoviocytes = 0

Mild hyperplasia = 1 Marked hyperplasia = 2

SEVERITY OF PATHOLOGY

Lining characteristics

(Tissue morphologic changes)

SECTION

AFFECTED

1/3 1/3 1/3

A Normal 0 0 0

B Short villi formation 1 2 3

C Finger-like projections 2 4 6

AA BB CC

Apparently normal

synovium = 0

Short villi formation = 1 Fronds-like projections = 2

Synovial Pathology:Synovial tissue morphologic changes

SEVERITY OF PAHTOLOGY

Cellular infiltration characteristics

SECTION

AFFECTED

1/3 1/3 1/3

A No inflammatory cell infiltration 0 0 0

B Mild to moderate inflammatory cell infiltration 1 2 3

C Marked inflammatory cell infiltration, lymphoid proliferation 2 4 6

AA BB CC

Synovial Pathology: Cellular infiltration

No cellular infiltrates = 0 Mild lymphocytic infiltrates

= 1

Lymphoid proliferation = 2

Meniscal Pathology: Sampling & Categories

Lateral Medial

3. Posterior

2. Middle

1. Anterior1

2

3

1

2

3

Cross section

of meniscus

Tissue Categories (use one or more)

Meniscus Meniscus structure

Matrix content

Cellular proliferation

Tissue sampling for histology

Meniscal Pathology

SEVERITY OF PATHOLOGY3 sections of med. & lat. meniscus

(anterior, middle, posterior if possible)

Tissue architecture Anterior 1/3 Middle Posterior 1/3

A Normal 0 0 0

B Mild disruption 1 1 1

C Moderate disruption with loss of tissue 2 2 2

D More than 50% loss of tissue architecture 3 3 3

Matrix Content

A Normal 0 0 0

B Mild alterations in matrix content 1 1 1

C Moderate alterations in matrix content 2 2 2

D Severe loss of matrix content 3 3 3

Proliferative Response

A None 0 0 0

B Mild proliferation of cells at synovial-meniscal junction 1 1 1

CProliferation of cells at synovial junction and extending into tissue or

along surface2 2 2

D Marked proliferation of cells involving majority of remaining tissue 3 3 3

c