Anterior cruciate ligament tunnel placement: Comparison of insertion site anatomy with the guidelines of a computer-assisted surgical system.

PURPOSE With the development of computer-assisted surgery (CAS) systems, the surgeon's ability to operate a CAS planning station will become essential. For example, default parameters in computed tomographic (CT) data are being used to place tunnels in anterior cruciate ligament (ACL) reconstruction. The goal of this study was to compare the location of the insertion sites in ACL reconstruction anatomically, via roentgenographic images and via CT scan data and to validate these tunnel placement parameters. TYPE OF STUDY Cadaveric analysis. METHODS Eight human cadaveric knees were marked with 6 copper wires 1 mm in diameter around the circumference of the insertions of the ACL. Using lateral roentgenograms and CT scans that were subsequently transferred to the CAS planning station, the tunnel locations were determined. These were based on a distance from the back of the condyle (location A) and from the roof of the notch (location B) on the femur and on a distance posterior from the tuberosity to the posterior margin along the tibial plateau, which is set as the CAS planning station's default. Locations according to roentgenograms and CT scans were then compared and the accuracy of the CAS planning station was assessed. RESULTS Comparison of roentgenograms and CT revealed a femoral insertion at 27.5% +/- 3.2% and 26.9% +/- 3.5% (roentgenograms) and 26.6% +/- 1.9% and 26.3% +/- 2.4% (CT), respectively. The CAS planning station provided a tunnel location that was 1.3 +/- 1.0 mm (0.3 to 2.5 mm) away from the actual femoral ACL insertion. The tibial tunnel was placed according to the copper wire markers and was found to be at 46.2% +/- 2.8% (roentgenograms) and 45.4% +/- 2.1% (CT). No statistical differences between position in CT and roentgenograms could be detected (P >.05). CONCLUSIONS The compared methodologies showed similar locations of the ACL insertions, assuring accurate preoperative planning with the CAS system. However, the CAS system requires adjustment to each individual knee anatomy.