Wk 1, Case 2 - Review

Patient History
11-year-old boy with a football-related medial collateral injury sprain that occurred one month ago

Findings
Menisci:

Medial meniscus: Unremarkable. Incidental intermeniscal ligament.

Lateral meniscus: Meniscal flounce adjacent to the anterior body/horn junction. No tear.

Ligaments:

Anterior cruciate ligament: Complete mid to proximal ACL transection. No tibial translation.

Posterior cruciate ligament: Intact.

Medial collateral ligament: Intact.

Lateral collateral ligament: Intact.

Posterolateral corner structures: Intact.

Extensor Mechanism:

Patellar tendon: Intact. No tendinosis or tear.

Distal quadriceps tendon: Small linear concealed intrasubstance delamination tear lateral distal tendon, measuring 1.3cm craniocaudal length and 0.7cm anterior to posterior.

Medial patellofemoral ligament: Intact.

Medial and lateral patellar retinacula: Intact.

Hoffa fat pad: Mild thickening of the ligamentum mucosum/infrapatellar plica. Focal edema within Hoffa’s fat pad superiorly. Appearances are likely to represent a degree of patellofemoral maltracking.
Articulations:

Patellofemoral compartment: Mild trochlear dysplasia with slight trochlear groove insufficiency. No patellar dysplasia. Preserved patellofemoral cartilage. No lateral patellar subluxation or tilt.

Medial compartment: Unremarkable.

Lateral compartment: Focal high-grade osteoedema/microtrabecular infraction adjacent to the minimally depressed sulcus terminalis. Mild osteoedema involving the posterolateral tibial metaphysis. Preserved femoral and tibial cartilage. No osteochondral defect.

General:

Bones:

Open growth plates.

Focal subchondral microtrabecular infraction adjacent to the minimally depressed sulcus terminalis as described above. Associated posterolateral tibial contusion, consistent with recent pivot shift mechanism of injury.

Focal well circumscribed subcortical/endosteal T1 hyperintense, T2 hyperintense lesion involving the proximal posterolateral femoral metaphysis, consistent with a nonaggressive fibrous endostial defect/fibrous cortical defect.

Incidental mildly dysplastic medial femoral condyle.

Effusion: Small to moderate-sized reactive suprapatellar effusion.

Baker’s cyst: None.

Loose bodies: None.

Other: Incidental reactive upper popliteal lymph node with normal fatty hilum (common in this age group).

Conclusion
Evidence for a recent pivot shift mechanism of injury with the following:

1. Complete ACL transection, without passive tibial translation in a patient with open growth plates.

2. Pivot shift pattern of microtrabecular injury involving the sulcus terminalis and posterolateral tibial plateau.

3. No meniscal tear. Incidental meniscal flounce adjacent to the anterior body/horn junction of the lateral meniscus.

4. Incidental nonaggressive posterolateral distal femoral metaphysis fibrous cortical defect/fibrous endosteal defect.