Anterior cruciate ligament (ACL) avulsion fractures or tibial eminence avulsion fractures are a type of avulsion fracture of the knee. This typically involves separation of the tibial attachment of the ACL to variable degrees. Separation at the femoral attachment is rare 5.
It is more common in children than adults.
They are usually caused by forceful hyperextension of the knee or by a direct blow over distal end of femur with the knee flexed.
Meyers and McKeevers classification
This classification was initially proposed by Meyers and McKeevers in 1959, and later has been modified by Zaricznyj in 19776, which at the time of writing (July 2016) remains the most widely used system of describing Anterior cruciate ligament avulsion fracture.
They are classified into four main types under the Meyers and McKeever system:
- type 1: minimally/nondisplaced fragment
- type 2: anterior elevation of the fragment
type 3: complete separation of the fragment
- type 3a: involves small portion of eminence
- type 3b: involves the majority of the eminence
- type 4: comminuted avulsion or a rotation of the fracture fragment
Depending on the type, a tibial avulsion is typically seen as a fracture fragment in variable orientation involving the tibial eminence. There may be anterior translation of the femur on the tibia on the lateral view.
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