0:00

Now if you deal with a process

0:03

in which there is weakening in the region

0:05

of the subcon bone plate

0:07

or subcon bone, you can get delamination

0:12

involving cartilage

0:14

and even portions of the subcon bone plate,

0:17

and hence in osteonecrosis shown on the left,

0:21

we can see such delamination

0:24

also involving the subc chondral bone plate.

0:27

And on your right, as I talked about earlier,

0:30

hyperparathyroidism with subc chondral bone resorption,

0:34

in addition to subperiosteal,

0:37

weakens this particular area such that with minor injury,

0:41

particularly in persons with chronic renal disease,

0:45

you can get delamination of cartilage

0:48

and portions of the subcon bone plate.

0:51

To finish our story of the articular cartilage,

0:54

before we talk about the subcon bone, some additional terms,

1:00

a flap, if you look it up, is something

1:02

that is attached loosely at one end only.

1:06

This would be a chondral flap.

1:09

A fragment is totally loose.

1:11

This is not a fragment, this is a flap.

1:15

A defect by definition, is something that is absent,

1:19

lacking, or deficient.

1:22

Here is a chondral defect, likely traumatic, owing

1:27

to the sharp margins.

1:29

More about that in a few minutes.

1:32

A fragment is something loose, broken off,

1:35

and completely free.

1:37

This is an osteochondral fragment in a posterior recess

1:41

of an ankle joint.

1:43

And indeed, as I showed you earlier in my ankle talk,

1:47

sometimes these fragments invert as shown here

1:51

classically in the ankle with involvement

1:54

of the lateral aspect of the Taylor Dome,

1:57

an inverted fragment composed of cartilage and bone.