Pathogenesis of the Segond fracture: anatomic and MR imaging evidence of an iliotibial tract or anterior oblique band avulsion.

PURPOSE

To demonstrate the normal anatomy of the stabilizing structures of the lateral aspect of the knee and to investigate pathogenesis of the Segond fracture, with emphasis on the iliotibial tract (ITT) and anterior oblique band (AOB) of the fibular collateral ligament.

MATERIALS AND METHODS

Dissection of the region of the AOB, ITT, and lateral capsular ligament was performed in three cadaveric knees, with placement of gadopentetate dimeglumine-filled tubes along their course and tibial insertions. These knees, in addition to three nondissected knees, were studied with magnetic resonance (MR) imaging by using standard and specialized oblique planes. Specimen sectioning provided anatomic correlation. Retrospective review of radiographs and MR images in 17 patients with acute Segond fractures was performed, and the relationship between the fragment and the demonstrated lateral supporting structures of the knee was noted.

RESULTS

Anatomic dissection and MR imaging of the cadaveric knees demonstrated a broad tibial insertion of the ITT, with fibers extending posterior to the Gerdy tubercle. A firm band of tissue, the AOB, extended from the fibular collateral ligament to the midportion of the lateral tibia, the typical site of a Segond fracture. The lateral capsular ligament proved to be a mere thickening of the capsule, inserting at the lateral tibia. Clinical analysis of acute Segond fractures confirmed the frequent attachment of the ITT and AOB to the avulsed fragment.

CONCLUSION

Anatomic and clinical findings suggest that fibers of the ITT and AOB are important factors in the pathogenesis of the Segond fracture.