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Segond fracture

A Segond fracture is an avulsion fracture of the knee which involves the lateral aspect of the tibial plateau, and is very frequently (~75% of cases) associated with disruption of the anterior cruciate ligament (see ACL tear). 

Clinical presentation

Contrary to the more common causes of an ACL tear, which typically involve a valgus stress 3, a Segond fracture typically occurs as a result of internal rotation and varus stress 1,4. Typically these injuries are seen in two settings:

  1. falls
  2. sports : especially skiing, basketball and baseball 4

Pathology

Somewhat surprisingly, the exact cause of a Segond fracture continues to be contentious. The conventional teaching has been that it is the result of avulsion of the middle third of the lateral capsular ligaments. Other candidate structures include the iliotibial band and anterior oblique band of the fibular collateral ligament 3

Radiographic features

Plain film

The classical appearance of a Segond fracture is that of a curvilinear or elliptic bone fragment projected parallel to the lateral aspect of the tibial plateau. This has been referred to as the lateral capsular sign 1 which is best seen on the straight anteroposterior view of the knee.

MRI

MRI is essential in all cases of Segond fractures to identify internal derangement. Disruption of the ACL is most common, however there are additional frequently encountered injuries. Associated injuries include1,3:

  • ACL tear
    • most common associated injury
    • 75-100% of cases 6
  • medial or lateral meniscal tear
    • 66-75% of cases 6
    • posterior horn most common 
  • avulsion of ACL from tibial attachment : rare
  • avulsion of fibular attachment of long head of biceps femoris
  • avulsion of the fibular collateral ligament

Treatment and prognosis

Although the fracture itself is small, the extensive ligamentous injury associated with it usually requires surgical intervention, to correct anterior rotational instability 4. Healing of the Segond fracture is associated with a characteristic bone excrescence arising below the lateral tibial plateau.

Etymology

First described by Paul Ferdinand Segond : French surgeon (1851 - 1912) based on cadaveric experiments 1-2,4.

Differential diagnosis

Imaging differential considerations include

  • arcuate sign : avulsion fracture of the head of the fibula 5 : fragment oriented more horizontally

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