Type:
Educational Exhibit
Keywords:
Bones, Musculoskeletal joint, Musculoskeletal system, CT, MR, Education, Trauma
Authors:
K. Singh, P. Jeremic, S. Singh
DOI:
10.26044/ranzcr2022/R-0163
Background
BACKGROUND:
Identifying the pattern of injury for underlying knee joint intenal derangment in the setting of trauma or degenerative change is important for patient management. One entity seen in the trauma setting is Posterolateral corner injury (PLC) of the knee which may predispose to instability and long term dysfunction if not accurately diagnosed.1The PLC provides the knee with stabalization during tibial external rotation during knee flexion. Imaging, particularly MRI, is vital in assessing the structures of the posterolateral corner and conventional 3T MRI in recent years has provided excellent anatomical delineation of the ligamentous structural integrity, bone architecture and joint assessment; thereby leading to apt diagnosis and subsequent treatment regime by orthopaedics.
Anatomically, the structural intergrity of the posterolateral corner comprises of important ligamentous structures which may be categorised into primary and dynamic stabilizers.2 There are disagreements amongst authors and no clear consensus of the formal constituents. The important structures include:
- Lateral Collateral ligament (LCL)
- Popliteus muscle
- Popliteofibular ligament
- Arcuate ligament complex (medial and lateral bands)
- Popliteomeniscal fascicles
- Fabellofibular ligament
- Biceps femoris muscle
- Iliotibial band
Of these structures, the LCL is the most important as it provides restraint to excessive varus stress and tensile strength and is regarded as a static stabalizer.3 The Popliteus muscle is an important structure as it functions to internal rotate the femur and unlock the knee on the initiation of flexion. It is closely asoociated with the three popliteomeniscal fasicles and popliteofibular ligament.
Plain radiographic imaging should raise suspicion for injury to the posterolateral corner and should precede cross sectional imaging in the emergency setting. The segond fracture and arcuate signs are important to keep in mind, as well as fractures of the anteromedial tibial plateau or anteromedial femoral condyles. It is vital to exclude neurovascular compromise as a first and foremost, and consideration of CT angiography should occur. 4
The mechanism of injury is usually related to direct trauma/axial load injury with hyperextension of the knee. Common activities that may result in injury include sports injuries, falls and vehicle accidents.