Radiographic analysis of femoral tunnel position in postoperative posterior cruciate ligament reconstruction

Purpose: The purpose of this study was to test the hypothesis that plain radiographs are accurate in assessing femoral tunnel positions in posterior cruciate ligament (PCL) reconstruction. Type of Study: Cadaveric study. Methods: Femoral tunnels were drilled in cadaveric distal femurs using standard techniques at the 12 o'clock, 1:30, and 3 o'clock positions in the left femora and at the 12 o'clock, 10:30, and 9 o'clock positions in the right femora. At each of the three positions, a 9-mm tunnel was drilled with its anterior edge 2 mm posterior to the articular surface of the medial femoral condyle (MFC). Posterior or "malpositioned" tunnels were drilled with the anterior edge I I rum posterior to the articular surface of the MFC. Four radiographs; a true lateral, a 10degrees externally rotated lateral, a 10degrees internally rotated film in the sagittal plane, and an anteroposterior (AP) radiograph were then taken of each tunnel with a radiopaque dilator in the tunnel. All radiographs were analyzed with the 4-quadrant method (4 is the posterior quadrant) and the ratio method (0 is anterior and 1 is posterior). The AP radiograph was measured using a new technique, the intersection of the angle of a line through the center of the femoral tunnel and a line placed tangential to the femoral condyles. Results: Means were calculated for each of the 6 tunnel positions on the 4 radiographs (lateral, external rotation, internal rotation, and AP). Of the 15 comparisons among tunnel postions, 13 could be discriminated using the lateral and AP radiographs. The high-anterior (HA) (12 o'clock position) could not be differentiated on any radiograph from the high-posterior (HP) (12 o'clock position). The internally rotated lateral radiograph could discriminate the midanterior (MA) (1:30 and 10:30 positions) from the low-anterior (LA) (the 3 and 9 o'clock positions). Conclusions: Three radiographs; the AP, lateral, and internally rotated lateral, can be used to detect a significant difference in the majority of tunnel locations. The tunnel positions that could not be differentiated with these measurements were posterior and may not be clinically important. We concluded that a plain radiograph is an accurate indicator of PCL tunnel position.