Wk 5, Case 1 - Review

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.