(Fig 2-B.28) Avulsion fractures of the fibular head (arcuate sign)

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 ✅Avulsion fractures of the fibular head (arcuate sign)

• Avulsion fractures of the fibular head, also known as the arcuate sign, are significant yet often not found in isolation. 
• These fractures typically occur alongside high-grade injuries to the Posterolateral Corner (PLC) of the knee, commonly accompanied by tears in the cruciate ligaments, the meniscus, and medial ligamentous structures. 
• The fibular head plays a crucial role as an anchor for the supportive structures in the PLC, making understanding its attachments essential for diagnosing the extent of injury and predicting the attached soft tissue structure based on the fracture's location and size.

1️⃣ Attachments to the Head of the Fibula:

• The biceps femoris tendon and lateral collateral ligament attach at the lateral margin of the fibular head and neck.
• The arcuate ligament and fabellofibular ligament are found more proximally and medially at the fibular head's posterior apex.
• The popliteofibular ligament attaches most medially at the posterior apex of the fibular head.

2️⃣ Avulsions of the Arcuate Complex:

• The most common avulsion pattern affects the fibular styloid process, where the arcuate complex (including the popliteofibular, arcuate, and fabellofibular ligaments) attaches.
• Injuries involving the arcuate or popliteofibular ligament often present a small fragment, ranging from 1 mm to 8 mm, displaced just medial and superior to the styloid process of the fibula.

3️⃣ Avulsions of the LCL and Biceps Femoris Tendon:

• Avulsion fractures resulting from injuries to the LCL and biceps femoris tendon are larger, affecting the lateral margin of the fibular head.
• Injuries to the fibular collateral ligament and/or biceps femoris tendon exhibit a fragment originating from the fibular head's lateral aspect, significantly larger in size, ranging from 1.5 cm to 2.5 cm.

 

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