0:00

So in this case we have a 23-year-old

0:03

with a hyperextension injury.

0:05

We see there's frontal and lateral projections of the knee,

0:10

and if we focus on our frontal projection, we can identify

0:15

that there is a small fragment here.

0:18

So this is our segun fracture.

0:20

So the segun fracture is an evulsion at the insertion

0:23

of this meniscal tibial aspect

0:25

of the lateral co ligament complex.

0:28

It's uh, really part of the joint capsule.

0:31

It has a high association

0:33

with anterior cruciate ligament tears and about 75%

0:37

and it's something that we detect best at radiography,

0:40

poorly visualized on the MRI exam that's done

0:43

for knee injury.

0:45

And so when you see this small little fracture fragment,

0:48

which looks pretty innocuous in and of itself, it

0:51

however portends something more serious

0:55

and that is a anterior cruciate ligament tear.

0:58

So now if we look at the MRI in this person,

1:01

we can see on the sagittal fat suppressed T two weighted

1:05

image that the ACL is not visualized.

1:08

There is fluid signal, uh, replacing the ACL.

1:12

The posterior crus ligament is partly visualized here.

1:15

And so this is a person with a complete ACL tear

1:19

and a segun fracture so

1:22

that saun fracture isn't AULs fracture involving the lateral

1:25

aspect of the tibial plateau has this high association

1:28

of approximately 75% with ACL disruptions.

1:31

The saun fracture occurs as a result

1:33

of the internal rotation

1:35

and virus stress,

1:37

whereas most ACL tears are due to valgus stress.

1:40

It can occur with a fall.

1:42

It can occur in sports such as skiing,

1:45

basketball, and baseball.

1:47

And conventional cause is thought to be an evulsion

1:49

of the middle third of the lateral capsular ligaments

1:53

and less likely a portion of the IT band

1:56

and anterior oblique band

1:57

of the fibular collateral ligament.

2:00

So the CI gun fracture presents

2:02

as a curve linear bone fragment lateral

2:05

to the lateral margin of the tibial plateau also is known

2:08

as the lateral capsular sign.

2:11

MRIs considered essential in all causes

2:13

to help identify the degree of internal derangement.

2:16

Again, about 75% will have an ACL tear

2:18

or an avulsion in that is also included meniscal tears.

2:22

So medial

2:23

or lateral meniscal tears typically of the posterior horn

2:26

as we see where the sagun fragment comes off of

2:29

that lateral capsule is also part of

2:32

where the fibular collateral ligament proper attaches.

2:36

So the MRI can help identify if there's AULs

2:39

of the fibular attachment of the long head

2:42

of the biceps tendon

2:43

or the fibular collateral ligament

2:45

that so-called conjoin tendon.

2:48

The treatment usually requires surgery

2:50

to correct the anterior rotational instability

2:53

that can be associated with this lesion.

2:56

Here is a schematic showing

2:59

A drawing of that segun fracture

3:01

where it comes off the lateral side

3:03

of the proximal tibia just distal to the tibial plateau.

3:07

So this diagram here shows a S of fracture

3:11

where you have an avulsion of

3:13

that tibial collateral ligament typically from the femoral

3:17

attachment site, so other lesions

3:19

that are associated with ACL tears.

3:22

So here the circle is pointing to a deepening of

3:25

that lateral condylar patellar sulcus.

3:28

And so this deepened sulcus is related to osteochondral

3:31

and patch that occurs.

3:34

And this is related to the ACL tear bone bruise pattern

3:37

where you get this pivot shift mechanism

3:39

of a lateral meniscus tear, impaction of the posterior horn,

3:44

plus or minus the valgus stress, and then an MCL

3:47

and a medial meniscus injury.