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 11 mm posterior to the articular surface of the MFC. Four radiographs; a true lateral, a 10° externally rotated lateral, a 10° 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.