Anatomic characteristics and radiographic references of the anterolateral and posteromedial bundles of the posterior cruciate ligament.

Background: Anatomic graft tunnel placement is reported to be essential in double-bundle posterior cruciate ligament (PCL) reconstruction. A measurement system that correlates anatomy and radiographs is lacking so far.

Purpose: To define the femoral and tibial attachments of the anterolateral (AL) and posteromedial (PM) bundles and to correlate them with digital and radiographic images to establish a radiographic anatomy based on anatomic landmarks and evaluate whether radiographs can serve as an accurate method for intraoperative and postoperative assessments of tunnel placement.

Study Design: Descriptive laboratory study.

Methods: Fifteen human cadaveric knee specimens were used. After preparation, the insertion areas of the 2 fiber bundles were marked with colorants, and high-definition digital images were obtained. With radiopaque tubes placed in the center of each bundle's footprint, anteroposterior and lateral radiographs were created. A measurement grid system was superimposed to determine the position of the AL and PM bundles' femoral and tibial insertion areas on both digital images and radiographs. The measurement zones were numbered 1 to 16, starting in the anterosuperior corner and ending in the posteroinferior corner.

Results: On radiographs and digital images, the femoral centers of the AL and PM bundles were found in zones 2 and 7, respectively. The tibial centers of the AL and PM bundles were found at 47.88% and 50.93%, respectively, of the total mediolateral diameter, 83.09% and 92.29%, respectively, of the total anteroposterior diameter, and 3.53 mm and 8.57 mm, respectively, inferior from the tibial plateau on radiographs.

Conclusion: This study provides a geometric characterization of the AL and PM bundles of the PCL and establishes a reliable and feasible correlation system between anatomy and radiography based on anatomic landmarks.

Clinical Relevance: Accurate definition of the insertion sites of the PCL is essential for anatomic double-bundle reconstruction. The results of our study may be used as a reference for intraoperative and postoperative assessments of correct femoral and tibial tunnel placements.