Radiographic landmarks for surgical reconstruction of the anterolateral ligament of the knee.

PURPOSE: To determine the radiographic landmarks of the anterolateral ligament (ALL) on the femur and tibia to assist in intraoperative graft placement during ALL reconstruction.

METHODS: The footprints of the ALL, fibular collateral ligament (FCL), popliteus insertion, lateral gastrocnemius insertion, and Gerdy's tubercle were isolated and centrally marked with tantalum beads in thirteen fresh-frozen cadaveric knees. Measurements were taken from the true lateral fluoroscopic images. On the femur, the mean distances from the ALL origin to the FCL origin and from the ALL origin to the popliteus insertion were measured. On the tibia, the mean distances from the ALL insertion to Gerdy's tubercle and from the ALL insertion to the lateral tibial plateau were measured. Furthermore, radiographic descriptions of the ALL origin and insertion were developed.

RESULTS: The ALL origin on the femur averaged 3.3 ± 1.5 mm anterior-distal to the FCL origin in one anatomical variant and 5.4 ± 1.4 mm posterior-proximal to the FCL origin in a second variant. The ALL origin was 9.9 ± 2.7 mm from the popliteus insertion. The ALL origin is described as overlying the posterior femoral cortical line, between Blumensaat's line and a line from the posterior condylar articular edge parallel to Blumensaat's line. The ALL insertion on the tibia averaged 24.7 ± 4.5 mm posterior to Gerdy's tubercle and 11.5 ± 2.9 mm distal to the lateral tibial plateau. The tibial ALL insertion is described between the posterior tibial cortical line and a parallel line drawn down from the apex of the tibial spine, and overlying a line drawn perpendicular to the posterior tibial cortical line starting from the apex of the posterior tibial condyles.

CONCLUSIONS: Using direct lateral fluoroscopy, radiographic landmarks of the ALL origin and insertion have been described.