Radiographic Landmarks for Tunnel Positioning in Posterior Cruciate Ligament Reconstructions

Background: Consistent radiographic guidelines for tunnel placement in single- or double-bundle posterior cruciate ligament (PCL) reconstructions are not well defined. Quantitative guidelines reporting the location of the individual PCL bundle attachments would aid in intraoperative tunnel placement and postoperative assessment of a PCL reconstruction. Hypothesis: Consistent and reproducible measurements in relation to radiographic landmarks for the entire PCL and its individual bundle attachments are achievable. Study Design: Controlled laboratory study. Methods: The femoral and tibial PCL bundle attachment centers of 20 nonpaired fresh-frozen cadaveric knees were labeled using radio-opaque spheres and the attachment areas were labeled using barium sulfate. Anteroposterior (AP) and lateral radiographs of the femur and tibia were obtained, and measurements of the distances between the PCL bundle centers and landmarks were acquired. Results: On the AP femur view, the anterolateral bundle (ALB) and posteromedial bundle (PMB) centers were 34.1 +/- 3.0 mm and 29.2 +/- 3.0 mm lateral to the most medial border of the medial femoral condyle, respectively. The lateral femur images revealed that the ALB center was 17.4 +/- 1.7 mm and the PMB center was 23.9 +/- 2.7 mm posteroproximal to a line perpendicular to the Blumensaat line that intersected the anterior margin of the medial femoral condyle cortex. Anteroposterior tibia images revealed that the ALB and PMB centers were located 0.2 +/- 2.1 mm proximal and 4.9 +/- 2.9 mm distal to the proximal joint line, respectively. The PCL attachment center was 1.6 +/- 2.5 mm distal to the proximal joint line. On the lateral tibia view, the ALB center was 8.4 +/- 1.8 mm, the PCL attachment center was 5.5 +/- 1.7 mm, and the PMB center was 2.5 +/- 1.5 mm superior to the champagne glass drop-off of the posterior tibia. Conclusion: Radiographic measurements from several clinically relevant views of the femur and tibia were reproducible with regard to the anatomic locations of the ALB and PMB centers. The measurements from the lateral femur and tibia views provided the most clinically pertinent radiographic measurements intraoperatively. Clinical Relevance: This study established a set of clinically relevant radiographic guidelines for anatomic reconstruction of the PCL. The parameters set forth in this study can be used in both the intraoperative and postoperative settings for both single-and double-bundle PCL reconstructions.