The purpose of this study was to investigate the relation of the Segond fracture with the anterolateral ligament (ALL) of the knee.

To identify the soft-tissue structure causative for the Segond fracture, a study was set up to compare anatomic details of the tibial insertion of the recently characterized ALL in cadaveric knees (n = 30) with radiologic data obtained from patients (n = 29) with a possible Segond fracture based on an imaging protocol search. The spatial relation of the ALL footprint with well-identifiable anatomic landmarks at the lateral aspect of the knee was determined, and this was repeated for the Segond fracture bed.

In all of the included cadaveric knees, a well-defined ALL was found as a distinct ligamentous structure connecting the lateral femoral epicondyle with the anterolateral proximal tibia. The mean distance of the center of the tibial ALL footprint to the center of the Gerdy tubercle (GT-ALL distance) measured 22.0 ± 4.0 mm. The imaging database search identified 26 patients diagnosed with a Segond fracture. The mean GT-Segond distance measured 22.4 ± 2.6 mm. The observed difference of 0.4 mm (95% confidence interval, -1.5 to 2.2 mm) between the GT-ALL distance and GT-Segond distance was neither statistically significant (P = .70) nor clinically relevant.

The results of this study confirmed the hypothesis that the ALL inserts in the region on the proximal tibia from where Segond fractures consistently avulse, thus suggesting that the Segond fracture is actually a bony avulsion of the ALL.

Although the Segond fracture remains a useful radiographic clue for indirect detection of anterior cruciate ligament injuries, the Segond fracture should be considered a frank ligamentous avulsion itself.