Radiographic analysis of femoral tunnel position in anterior cruciate ligament reconstruction

Successful reconstruction of the anterior cruciate ligament (ACL) depends on anatomic placement of a graft ligament substitute. This study examined the accuracy of a plain radiograph in determining femoral tunnel position during ACL reconstruction. Nine cadaveric distal femurs had six separate tunnels made in each specimen: 12:00 (high position), 1:30 (anatomic position), and 3:00 (low position) in the left femora and 12:00 (high), 10:30 (anatomic), and 9:00 (low) in the right femora. At each position on the clock face, two 9-mm tunnels were drilled, leaving 2 mm (correct) and 12 mm (incorrect) of posterior wall intact. With a radiopaque tunnel dilator in each tunnel, a true lateral radiograph, a 10 degree externally rotated lateral radiograph, and a 10 degree internally rotated lateral radiograph were obtained. All radiographs were analyzed for femoral tunnel placement in the anteroposterior plane with the four-quadrant method described by Harner et al and the ratio method described by Aglietti et al. Statistically significant differences could only be distinguished between anatomic (10:30), anterior (12-mm rim), and posterior (2-mm rim) positions. There were no statistically significant differences for any of the other positions when comparing true laterals to true laterals, true laterals to internal or external oblique views, or when comparing internal and external oblique views. A malpositioned anterior tunnel (12-mm rim posterior), which was "low" at 9:00 or "high" at 12:00 in the notch (malplaced), could not be distinguished reliably from an anatomically correct placed tunnel with a single-plane lateral radiograph.