Abstract
Aim: To determine optimal tibial tunnel orientation that projected onto isometric positions of the LFC.
Methods: Tibial tunnels were described by transverse rotations about tibial long axes, angles of elevation and tilt. In each of 8 cadaver knees, 18 tibial positions were drilled with 2mm wires to exit at the centre and posterior end of the tibial footprint. The linear projections of these wires onto the LFC were marked by 1.6mm wires and were described as x-y co-ordinates with reference to the geometric centre of the LFC.
Results: The isometric femoral tunnel positions were approximated (within a 2mm radius) by tibial tunnels rotated 39.3°, elevated 55.7°, exiting at the posterior end of the footprint with knees flexed 90°. Tunnels rotated between 20–45° and elevated 60° had highest probability of isometric projection and those that exited at the centre of the footprint could not be linearly projected anywhere near the isometric point. Applying 50N posterior force on the tibia brought the projections proximally by 4.1mm (p=0.001).
Conclusion: Transtibial tunnel directions are known to affect siting of femoral tunnels, and hence outcome of ACL surgery. This study demonstrated the orientation of tibial tunnels that could linearly project to isometric femoral tunnel positions.
The abstracts were prepared by Mr Roger Smith. Correspondence should be addressed to him at the British Association for Surgery of the Knee, c/o BOA, Royal College of Surgeons of England, 35–43 Lincoln’s Inn Fields, London WC2A 3PN.
