0:00

Okay, here we are.

0:02

23-year-old, sustained a fall a few weeks ago.

0:06

Now, we have findings in the posterolateral corner

0:11

that are worth looking at a little more carefully.

0:16

As we follow the cortical outline of the lateral

0:20

tibial plateau, at the expected side

0:23

of insertion of the anterolateral ligament,

0:25

which is the reinforcement of the

0:27

lateral knee joint capsule.

0:30

Consider there is this small avulsion fracture

0:35

with a cortical fragment

0:37

displaced away from the donor side,

0:41

and this is the marrow edema outlining

0:44

the side of fracture.

0:46

I have parked myself on the coronal images

0:50

to show you exactly that same point.

0:53

So, we have these shell of bone that has been

0:59

detached from the lateral tibial plateau at the

1:03

insertion of the lateral knee joint capsule,

1:06

where the anterolateral ligament leaves.

1:10

On fat sat sequences,

1:12

this one is actually a coronal T1-weighted sequence.

1:16

We can see the defect,

1:18

the cortical defect and the marrow edema

1:21

associated with this fracture.

1:24

This is a segond fracture.

1:27

Segond fractures are typically seen in the setting

1:31

of anterior crucial ligament here.

1:34

So, this patient has complete absence of the

1:37

anterior cruciate ligament fibers

1:39

here in the lateral intercondylar notch.

1:42

So, the rule is applying here.

1:45

Greater than 75% of patients with segon fractures

1:50

are going to have a full thickness tear

1:53

of the anterior cruciate ligament.

1:55

There are some other secondary signs associated

1:59

with this type of pivot shift trauma

2:02

that we have reviewed before,

2:04

but I think it's worth mentioning.

2:06

We see a pattern of contusions in the lateral

2:11

compartment with the posterior aspect of the

2:14

lateral tibial plateau having a

2:16

large area of marrow edema.

2:18

And then, we look for the reciprocating contusion

2:22

in the lateral femoral condyle around

2:25

the area of the sulcus terminalis.

2:27

So, this is the sulcus terminalis of the lateral

2:30

femoral condyle, reciprocating impaction injuries.

2:34

Now, looking at the other players in

2:37

the posterolateral corner,

2:38

we have the fibular collateral ligament with

2:41

sprain of its fibers towards insertion

2:44

into the fibular head.

2:46

The fibular head has a marrow contusion, as well.

2:50

This is not infrequently seen,

2:52

and we should seek for findings in the fibular head,

2:55

particularly the presence of an avulsion,

2:58

arcuate sign at the side of insertion of the

3:02

smaller posterolateral corner ligaments,

3:05

including the arcuate ligament,

3:07

hence the name "Arcuate sign."

Wk 5, Case 1 - Review

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0:00

Okay, here we are.

0:02

23-year-old, sustained a fall a few weeks ago.

0:06

Now, we have findings in the posterolateral corner

0:11

that are worth looking at a little more carefully.

0:16

As we follow the cortical outline of the lateral

0:20

tibial plateau, at the expected side

0:23

of insertion of the anterolateral ligament,

0:25

which is the reinforcement of the

0:27

lateral knee joint capsule.

0:30

Consider there is this small avulsion fracture

0:35

with a cortical fragment

0:37

displaced away from the donor side,

0:41

and this is the marrow edema outlining

0:44

the side of fracture.

0:46

I have parked myself on the coronal images

0:50

to show you exactly that same point.

0:53

So, we have these shell of bone that has been

0:59

detached from the lateral tibial plateau at the

1:03

insertion of the lateral knee joint capsule,

1:06

where the anterolateral ligament leaves.

1:10

On fat sat sequences,

1:12

this one is actually a coronal T1-weighted sequence.

1:16

We can see the defect,

1:18

the cortical defect and the marrow edema

1:21

associated with this fracture.

1:24

This is a segond fracture.

1:27

Segond fractures are typically seen in the setting

1:31

of anterior crucial ligament here.

1:34

So, this patient has complete absence of the

1:37

anterior cruciate ligament fibers

1:39

here in the lateral intercondylar notch.

1:42

So, the rule is applying here.

1:45

Greater than 75% of patients with segon fractures

1:50

are going to have a full thickness tear

1:53

of the anterior cruciate ligament.

1:55

There are some other secondary signs associated

1:59

with this type of pivot shift trauma

2:02

that we have reviewed before,

2:04

but I think it's worth mentioning.

2:06

We see a pattern of contusions in the lateral

2:11

compartment with the posterior aspect of the

2:14

lateral tibial plateau having a

2:16

large area of marrow edema.

2:18

And then, we look for the reciprocating contusion

2:22

in the lateral femoral condyle around

2:25

the area of the sulcus terminalis.

2:27

So, this is the sulcus terminalis of the lateral

2:30

femoral condyle, reciprocating impaction injuries.

2:34

Now, looking at the other players in

2:37

the posterolateral corner,

2:38

we have the fibular collateral ligament with

2:41

sprain of its fibers towards insertion

2:44

into the fibular head.

2:46

The fibular head has a marrow contusion, as well.

2:50

This is not infrequently seen,

2:52

and we should seek for findings in the fibular head,

2:55

particularly the presence of an avulsion,

2:58

arcuate sign at the side of insertion of the

3:02

smaller posterolateral corner ligaments,

3:05

including the arcuate ligament,

3:07

hence the name "Arcuate sign."

Report

Patient History
23-year-old woman with acute right medial and lateral knee pain and weakness since a fall 2 weeks prior. Question ACL tear.

Findings
Menisci:

Medial Meniscus: Intact.

Lateral Meniscus: Intact.

Ligaments:

Anterior Cruciate Ligament: High-grade full-thickness midsubstance tear with associated passive anterior tibial translation consistent with ACL deficiency.

Posterior Cruciate Ligament: Intact.

Medial Collateral Ligament: Periligamentous edema with anterior partial-thickness tear of the tibial collateral ligament, consistent with intermediate (grade 2) injury. Tear extends into the femoral origin of the medial patellofemoral ligament. Diffusely sprained swollen medial meniscofemoral ligament anteriorly.

Lateral Collateral Ligament: Thickening and increased intrasubstance signal within the proximal fibular collateral ligament consistent with intermediate grade sprain.

Posterolateral Corner Structures: Complete tear popliteofibular ligament with “mermaid sign”. Swollen and thickened partially torn arcuate ligament. Disruption of the inferior lateral popliteal meniscal fascicles. Swollen proximal popliteus tendon with partial thickness tear in the popliteus hiatus. Popliteus myotendinous junction unremarkable.

Posteromedial Corner Structures: Unremarkable.

Extensor Mechanism:

Patellar Tendon: Mildly redundant and lax with tortuosity of the distal tendon.

Distal Quadriceps Tendon: Intact and unremarkable appearance.
Medial Patellofemoral Ligament: High-grade tear of the femoral origin of the medial patellofemoral ligament.

Medial and Lateral Patellar Retinacula: Swollen but intact

Hoffa’s Fat Pad: Unremarkable.

Articulations:

Patellofemoral Compartment: No intermediate or high-grade chondromalacia. No traumatic osteochondral lesion. Moderately lateralized patella with lateral patellar tilt suggesting patellofemoral maltracking. Borderline increased TT-TG distance measuring 1.6 cm. Suspect patella alta during quadriceps contraction with an elongated tortuous lax patellar tendon.

Medial Compartment: Unremarkable.

Lateral Compartment: No intermediate or high-grade chondromalacia. See below for osseous contusion pattern.

General:
Bones: Pivot-shift pattern of osseous injury with contusion of the lateral femoral condyle/sulcus terminalis and posterolateral tibial plateau microtrabecular fracture with osteoedema/contusion. A mildly distracted 7 mm avulsed cortical fragment is seen at the lateral rim of the lateral tibia, posterosuperior to Gerdy tubercle, consistent with a Segond fracture. Intrasubstance partial-thickness tear of the anterolateral or anterior oblique band of the fibular collateral ligament/lateral capsular Segond ligament.

Effusion: Large suprapatellar hemarthrosis.

Baker Cyst: Evidence for recent Baker cyst rupture with extensive extravasated fluid seen superficial to the medial and lateral heads of the gastrocnemius and extending down myofascial planes deep to the medial head of the gastrocnemius.

Loose Bodies: None.

Soft tissue and Neurovascular: Unremarkable.
Conclusion
Evidence for recent pivot-shift mechanism of injury with the following:

1.Complete full-thickness midsubstance ACL tear with associated passive anterior tibial translation (consistent with ACL deficiency).
2.Grade 2 MCL sprain with partial thickness tear anteriorly, extending to involve the femoral origin of the medial patellofemoral ligament.
3.Segond fracture and anterolateral ligament/Segond ligament sprain with posterolateral corner injury/instability evident as popliteofibular ligament complete tear, proximal popliteus tendon partial tear, arcuate ligament partial tear and disrupted inferior meniscopopliteal fascicles.
4.Pivot-shift pattern of bone marrow contusions involving the sulcus terminalis and posterolateral tibial plateau.
5.No traumatic meniscal tear.

Case Discussion

Faculty

Omer Awan, MD, MPH, CIIP

Associate Professor of Radiology

University of Maryland School of Medicine

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Jenny T Bencardino, MD

Vice-Chair, Academic Affairs Department of Radiology

Montefiore Radiology

Edward Smitaman, MD

Clinical Associate Professor

University of California San Diego

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Wk 5, Case 1 - Review