0:00

So, this is a 20-year-old man who sustained

0:05

acute trauma to his knee.

0:07

And the main finding here is an

0:10

avulsion of the tbial spine.

0:13

At the insertion of the anterior cruciate ligament.

0:17

So we are following bloom's dot line,

0:19

the roof of the intercondylar notch.

0:23

We see the fibers of the ACL.

0:26

And then, abruptly, there is disruption

0:29

of the cortical line.

0:31

Along the anterior aspect of the

0:34

tibial intercondylar eminence.

0:37

Low signal intensity fragment has been pulled off

0:42

from the intercondylar eminence,

0:44

and is attached to the swollen edematous,

0:48

anterior cruciate ligament.

0:50

Now, there is a classification

0:53

for anterior tibial avulsions,

0:54

and this would be a type 3B,

0:59

where the fragment is completely

1:01

detached from the donor side.

1:03

And it's more than half of the distance between

1:08

the anterior and posterior

1:09

portion of the fragment.

1:11

So, a type A would be less than a half

1:14

of the fragment is detached.

1:17

And type 3B, which this one is,

1:20

the fragment is completely detached

1:23

and displaced from the donor site.

1:25

There is no major fragmentation or comminution.

1:29

So that makes it a three, not a four.

1:32

On the coronal images,

1:34

we see the fracture pattern extending

1:37

through the base of the tibial spine,

1:40

at the site of insertion of the

1:42

anterior crucial ligament.

1:45

Typical findings of anterior crucial ligament injury,

1:49

including pivot shift,

1:52

reciprocating impaction injuries

1:54

in the lateral femoral condyle,

1:57

posterior aspect of the lateral tibial plateau,

2:02

as well as smaller bone marrow contusions

2:05

on the medial side,

2:06

reciprocating impaction injuries that happen when

2:10

the tibia translates anteriorly on the

2:13

femur and then recoils back.

2:16

And the posterior aspect of the tibia is going

2:18

to hit the femoral condyles.

2:20

Now,

2:21

this projection is an oblique coronal

2:25

T2-weighted sequence

2:27

to better assess the health of the anterior

2:30

cruciate ligament.

2:31

And as we described before,

2:33

the fibers are intact.

2:34

What is disrupted is the attachment to

2:38

the bone with an avulsion fragment

2:41

that is displaced from the donor site.

2:44

So, in summary,

2:46

fracture of the tibial spine in the setting of pivot shift trauma

2:52

with edema of the fibers

2:54

of the anterior cruciate ligament,

2:56

but no ligamentous disruption.

2:59

Close.

Wk 4, Case 3 - Review

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Interactive Transcript

Pro Tip: Click on a word in the transcript to jump to that point in the video

0:00

So, this is a 20-year-old man who sustained

0:05

acute trauma to his knee.

0:07

And the main finding here is an

0:10

avulsion of the tbial spine.

0:13

At the insertion of the anterior cruciate ligament.

0:17

So we are following bloom's dot line,

0:19

the roof of the intercondylar notch.

0:23

We see the fibers of the ACL.

0:26

And then, abruptly, there is disruption

0:29

of the cortical line.

0:31

Along the anterior aspect of the

0:34

tibial intercondylar eminence.

0:37

Low signal intensity fragment has been pulled off

0:42

from the intercondylar eminence,

0:44

and is attached to the swollen edematous,

0:48

anterior cruciate ligament.

0:50

Now, there is a classification

0:53

for anterior tibial avulsions,

0:54

and this would be a type 3B,

0:59

where the fragment is completely

1:01

detached from the donor side.

1:03

And it's more than half of the distance between

1:08

the anterior and posterior

1:09

portion of the fragment.

1:11

So, a type A would be less than a half

1:14

of the fragment is detached.

1:17

And type 3B, which this one is,

1:20

the fragment is completely detached

1:23

and displaced from the donor site.

1:25

There is no major fragmentation or comminution.

1:29

So that makes it a three, not a four.

1:32

On the coronal images,

1:34

we see the fracture pattern extending

1:37

through the base of the tibial spine,

1:40

at the site of insertion of the

1:42

anterior crucial ligament.

1:45

Typical findings of anterior crucial ligament injury,

1:49

including pivot shift,

1:52

reciprocating impaction injuries

1:54

in the lateral femoral condyle,

1:57

posterior aspect of the lateral tibial plateau,

2:02

as well as smaller bone marrow contusions

2:05

on the medial side,

2:06

reciprocating impaction injuries that happen when

2:10

the tibia translates anteriorly on the

2:13

femur and then recoils back.

2:16

And the posterior aspect of the tibia is going

2:18

to hit the femoral condyles.

2:20

Now,

2:21

this projection is an oblique coronal

2:25

T2-weighted sequence

2:27

to better assess the health of the anterior

2:30

cruciate ligament.

2:31

And as we described before,

2:33

the fibers are intact.

2:34

What is disrupted is the attachment to

2:38

the bone with an avulsion fragment

2:41

that is displaced from the donor site.

2:44

So, in summary,

2:46

fracture of the tibial spine in the setting of pivot shift trauma

2:52

with edema of the fibers

2:54

of the anterior cruciate ligament,

2:56

but no ligamentous disruption.

2:59

Close.

Report

Patient History
30-year-old female with left knee pain and swelling after skiing injury.

Findings
Menisci:

Medial Meniscus: Upper surface peripheral rim posteromedial tear at the meniscocapsular junction (ramp type lesion). Anterior root attached to a small avulsed osseous fragment of the anterior tibial spine, related to an ACL footprint avulsion injury.

Lateral Meniscus: Small Wrisberg rip tear.

Ligaments:

Anterior Cruciate Ligament: Comminuted mildly displaced distal ACL footplate avulsion fracture. Anterior root of the medial meniscus attached to the most medial avulsed osseous fragment. No interposition of the menisci or transverse intrameniscal ligament between osseous fragments. The ACL itself is intact but slightly swollen with periligamentous edema suggesting low-grade sprain.

Posterior Cruciate Ligament: Intact.

Medial Collateral Ligament: Diffuse periligamentous edema surrounding the tibial collateral ligament with slightly thickened proximal portion and increased intraligamentous signal, consistent with a low to intermediate grade sprain (grade 1-2 injury).

Lateral Collateral Ligament: Mild periligamentous edema consistent with a low-grade proximal injury.

Posterolateral Corner Structures: Intact.

Posteromedial Corner Structures: Poseromedial meniscocapsular junction injury.

Extensor Mechanism:

Patellar Tendon: Intact.

Distal Quadriceps Tendon: Intact.

Medial Patellofemoral Ligament: Intact.

Medial and Lateral Patellar Retinacula: Intact.

Hoffa’s Fat Pad: Incidental focal superolateral Hoffa’s fat pad edema consistent with patellofemoral maltracking with a degree of patellar tendon-lateral femoral condyle friction syndrome or contusion.

Articulations:

Patellofemoral Compartment: Low-grade trochlear dysplasia with slight trochlear sulcus insufficiency (Dejour A). Slightly dysplastic patella with elongated odd patellar facet. Mild lateral patellar tilt and subluxation. No intermediate or high-grade chondromalacia patella.

Medial Compartment: Comminuted distal ACL footplate avulsion fracture extending into the lateral aspect of the medial tibial plateau, adjacent to the tibial eminence. No cortical step at the tibial plateau.

Lateral Compartment: Comminuted fracture extends to the junction of the tibial eminence and medial aspect of the tibial plateau.

General:

Bones:

Comminuted mildly displaced distal ACL footplate avulsion fracture, involving the anterior tibial eminence, measuring approximately 21 mm in diameter. Associated surrounding high-grade osteoedema extending into the proximal lateral tibial metaphysis.

A pivot-shift pattern of marrow edema is seen involving the sulcus terminalis/lateral femoral condyle and posterolateral tibial plateau and fibular styloid. Osseous contusions with marrow edema seen involving the posteromedial tibial plateau and medial femoral condyle.

Minimally impacted 7 x 6 mm fracture of the posterior aspect of the lateral tibial plateau.

Effusion: Large suprapatellar effusion/hemarthrosis.

Baker’s Cyst: Small Baker’s cyst without dehiscence or rupture.

Loose Bodies: At least 3 small avulsed cortical fragments are seen adjacent to the anterior tibial eminence (largest measuring 6 mm).

Soft tissue and neurovascular: Unremarkable.

Conclusion
Pivot-shift mechanism of injury with the following:

1. Distal ACL tibial footplate comminuted destructive avulsion fracture (Meyers and McKeever type IV avulsion). ACL intact but demonstrating low-grade sprain. Recommend CT for further characterization of osseous fragments.
2. Anterior root lateral meniscus avulsed with a small osseous fragments adjacent to the ACL footprint avulsion. No meniscal or transverse intrameniscal ligament entrapment.
3. Small Wrisberg rip tear posterior horn lateral meniscus and ramp lesion posterior horn medial meniscus.
4. Low to intermediate grade (grade 1-2) sprain MCL.
5.Pivot-shift mechanism of osseous contusions involving the medial and lateral compartment as described. Minimally impacted 7 x 6 mm fracture of the posterior aspect of the lateral tibial plateau.

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 4, Case 3 - Review