ch 73 Osteochondrosis Flashcards
osteochondrosis latens
early microscopic cartilaginous lesion
osteochondrosis manifesta
subclinical lesion that is macroscopically and radiographically apparent
osteochondrosis dissicants
disease if attached or loose cartilage flap is present
when is there first evidence of skeletons on radiographs
19-25 days post fertilization
growth plates contribute to ____ % of final bone length
75-80%
eiphysis contributes approximately _____ % of final bone length
20-25%
what is the incidence of osteochondrosis
8.1/1000pt
sex predisposition for OCD
males except for talus OCD
most common OCD locations in dogs
caudal humeral head
medial humeral condyle
lateral femoral condyle
medial or lateral trochlear ridge of the talus
most common OCD locations in cats
Centro-caudal aspect of proximal humeral condyle,
lateral femoral condyle
by what process do joints form between developing bones
segmentation and cavitation
when does the majority of longitudinal growth take place?
12-26wks
how do growth plates enlarger
via formation of new cartilage
what determines volume of newly formed cartilage
chondrocyte proliferation
chondrocyte enlargement
matrix formation
Humerus, diaphysis
age when ossification center appears
age when fusion occurs
birth
Humerus (proximal epiphysis)
age when ossification center appears
age when fusion occurs
1-2 wk
10-13 mo
Humerus (distal epiphysis)
age when ossification center appears
age when fusion occurs
1-2 wks
6-8 mo to shaft
Humerus (medial condyle)
age when ossification center appears
age when fusion occurs
2-3 wks
6wks to lateral condyle
Humerus (lateral condyle)
age when ossification center appears
age when fusion occurs
2-3 wks
Humerus (medial epicondyle)
age when ossification center appears
age when fusion occurs
6-8 wks
6 months to condyle
Radius (diaphysis)
age when ossification center appears
age when fusion occurs
birth
Radius (proximal epiphysis)
age when ossification center appears
age when fusion occurs
3-5 weeks
6-11 months
Radius (distal epiphysis )
age when ossification center appears
age when fusion occurs
2-4 weeks
8-12months
Ulna (diaphysis)
age when ossification center appears
age when fusion occurs
birth
Ulna (olecranon)
age when ossification center appears
age when fusion occurs
8 wk
6-10 month
Ulna (distal epiphysis)
age when ossification center appears
age when fusion occurs
8 wks
8-12 months
Femur (diaphysis)
age when ossification center appears
birth
Femur (proximal epiphysis)
age when ossification center appears
age when fusion occurs
2 weeks
7-11months
Femur (trochanter major)
age when ossification center appears
age when fusion occurs
8 weeks
6-10months
Femur (trochanter minor)
age when ossification center appears
age when fusion occurs
8 wk
8-13months
Femur (distal epiphysis)
age when ossification center appears
age when fusion occurs
8-11 months (fusion)
Femur (trochlea)
age when ossification center appears
age when fusion occurs
2 weeks
3 mo condyle to trochlea
Femur (medial condyle)
age when ossification center appears
3 wk
Femur (lateral condyle)
age when ossification center appears
3 wk
Tibia (diaphysis)
age when ossification center appears
birth
Tibia (medial condyle)
age when ossification center appears
age when fusion occurs
3 wk
6 wk to lateral condyle
Tibia (lateral condyle)
age when ossification center appears
age when fusion occurs
3 wk
6-12 mo to shaft
Tibia (tuberosity)
age when ossification center appears
age when fusion occurs
8 wk
6-8 mon to condyle
6-12 mo to shaft
Tibia (distal epiphysis)
age when ossification center appears
age when fusion occurs
3 wk
8-11mo
Tibia (malleolus)
age when ossification center appears
age when fusion occurs
3 mo
5mo
fibula (diaphysis)
age when ossification center appears
birth
fibula (proximal epiphysis)
age when ossification center appears
age when fusion occurs
9 wk
8-12 month
fibula (distal epiphysis)
age when ossification center appears
age when fusion occurs
2-7 wk
5 month
Talus
age when ossification center appears
birth - 1 wk
fibular
age when ossification center appears
birth-1wk
define saltation
short period of active growth
Hueter-Volkmann law
Proposes the growth is impeded by increased mechanical compression and accelerated by reduced loading
what is expansion of the growth plate constrained by
ring of Lacroix
Does Chondrocytic proliferation and matrix synthesis occur primarily in the daytime or nighttime?
daytime
Does active mineralization primarily ocur in the daytime or nighttime?
nighttime
What is the appearance and characteristics of cells in the resting zone of the growth plate cartilage
Chondrocytes are small, randomly orientated and scattered irregularly through the matrix
Cells divide slowly
What is the appearance and characteristics of cells in the proliferative zone of the growth plate cartilage
chondrocytes are flat and relatively small
organized in columns
chondrocytes divide, slowly enlarge, and synthesize matrix
What is the appearance and characteristics of cells in the hypertrophic zone of the growth plate cartilage
chondrocytes are spheroid and relatively large
cells RAPIDLY enlarge
What are the appearance and characteristics of cells in the mineralization zone of the growth plate cartilage?
chondrocytes have obtained their final size/shape
newly formed matrix mineralizes
what stimulates clonal expansion of chondrocytes in the proliferation zone
IGF-1
what are the requirements for change into hypertrophic chondrocyte phenotype
Bone morphogenetic protein (BMP), Wnt/𝛽 catenin, Runx2, Runx 3, thyroid hormone, and other regulators
during the process of endochondral ossification, who produces VEGF and what does VEGF control
produced by hypertrophic chondrocytes
controls vascular ingrowth
what is enlargement of the epiphysis a function of
Chondrocyte proliferation
Chondrocyte enlargement
Matrix formation
Duration of chondrogenic activity in the chondro-epiphysis
where do vessels of the chondro-epiphysis juncture originate from
perichondral plexus
vessels course within cartilage canals
what is the heritability of OCD
10-45%
Over-feeding is thought to cause stimulation of chondrocyte differentiation and proliferation via elevated hormones including…….
Elevated levels of growth hormone
IGF-1 triiodothyronine (T3)
Thyroxine (T4)
Insulin
what are the zones of mature articular cartilage
superficial zone
transitional zone
radial zone
zone of calcified cartilage
what are the differences between the inner layer and the growth plate
Inner layer is visually disorganized and does not have the ordered zonal and columnar arrangemen of the growth plate
Chondroepiphysis has an abundant vasculature
when does the majority of longitudinal growth take place?
12-26 wks
how to growth plates enlarge
via formation of new cartilage
how does the increase in cartilage volume result in bone length growth
pushing articular-epiphyseal complex away from the metaphysis
where is the newly formed cartilage converted into bone
Junction of growth plate and metaphysis via endochondral ossification
who produces IGF-1
daughter cells in the resting zone
what role do osteoclasts play in endochondral ossification
remove transverse matrix septa that separates apoptotoic hypertrophic chondrocytes from metaphyseal vasculature, leaving voids lacunae for new vessels to form
What is the role of osteoprogenitor cells?
Differentiate into osteoblasts→lay down woven bone on calcified cartilage matrix, forming lattice of calcified cartilage and woven bone (=primary spongiosa)
What is secondary spongiosa?
Lamellar bone that replaces the calcified cartilage (primary spongiosa) and woven bone
What are the layers of the articular-epiphyseal complex?
Thin outer layer, thicker inner layer
Characterize the outer layer
Contains avascular specialized immature articular cartilage that will mature into articular cartilage; has no role in endochondral ossification
Characterize the inner layer
Functionally similar to the growth plate, responsible for epiphyseal enlargement and mineralization of new cartilage
What are the zones of the outer layer of the articular-epiphyseal complex (secondary ossification center)?
Superficial zone, transitional zone, radial zone, and zone of calcified cartilage
What is the radial zone?
Uncalcified cartilage
What separates radial zone from the zone of calcified cartilage?
The tidemark
What does the tidemark represent?
Completion of maturation process of the ossification zone
Where does chondrocyte proliferation take place within epiphysis?
on the periphery
Where does maturation take place?
Toward the center
What is chondrification?
Redundant cartilage canals regress as the ossification front moves from center of epiphysis to newly formed epiphyseal cartilage
What risk factors play a role in osteochondrosis?
Heredity, rapid growth, dietary factors, trauma
How might microtrauma cause ununited anconeal processes?
Overgrowth of radius may cause shear forces in growth plate of anconeal process
What is the primary lesion of osteochondrosis?
Unknown - proposed Focal necrosis of epiphyseal cartilage canals→cartilage ischemia and necrosis vs dyschondroplasia vs relative osteopenia
At what point does the proposed causes of OCD (primary) occur?
At a point in development when the vessels originating from the perichondrium are being replaced by vessels from adjacent epiphyseal bone marrow
How might the necrotic focus heal?
Through stages of granulation tissue and intramembranous ossification or deforms and becomes altered joint congruency, subchondral bone cyst, or fissure/cleft
How are OCD lesions graded?
I cartilage surface normal, cartilage slightly thickened, minuscule subchondral defect
II cartilage surface mottled; cartilage more thickened
III discoid elevation of cartilage surface, large cleft, sclerotic subchondral bone
IV typical partially detached cartilage flap or separated flap and joint mice
What are type I flaps vs type II flaps involving articular epiphyseal region?
Type 1 – occur at center of affected surface, away from vascular attachments (caudal humeral head, medial humeral condyle, medial or lateral femoral condyle)
Type 2- occur at joint margin, retain vascular attachments (talar ridges, coronoid process)
How do type II flaps heal?
Endochondral ossification
What is failure of endochondral ossification (osteochondrosis) characterized by if affecting the growth plate rather than articular surface?
Persistence of hypertrophic chondrocytes
What is a retained cartilaginous core?
Local thickening of a growth plate
What is found in the retained cartilage core?
Focal thickening of the growth plate , characterized by persistent, viable hypertrophic chondrocytes
What are the proposed mechanism of retained cartilaginous cores occurring?
Damage to resting zone cartilage canals or metaphyseal blood supply
What does damage to resting zone cartilage canals or metaphyseal blood supply cause?
Inhibits conversion of mineralized growth plate cartilage into metaphyseal bone , resulting in thickening of the hypertrophic zone of the growth plate
When are retained cartilaginous cores of clinical consequence?
When they are associated w/reduced length of the ulna with secondary deformities (bowing)
What is consequence of ulnar cartilaginous core (growth plate OC)?
Radial procurvatum, carpal valgus, elbow incongruity, short ulna
How do articular flaps heal following detachment?
Fibrocartilage
