Poor outcome in ACL reconstruction is often related to tunnel position. This study investigates the use of surgical navigation to improve outcome. Improving accuracy of tunnel position will lead to improved outcome.

In a prospective randomised controlled trial 60 ACL plasties with quadruple-loop semi-tendinosus and gracilis tendon were randomised to either standard instrumentation or computer assisted guides to position the tibial and femoral tunnels. The results were evaluated on clinical outcome based on IKDC laxity measurements and radiologic assessment of anterior drawer at 150 and 200N as well as radiological assessment of the tunnel positions.

No complications were observed in either group. IKDC laxity was level A in 22 knees in the conventional group (average 1.5 mm (0-6) at 200N) compared with 26 navigated knees (average laxity 1.3mm (0-5)). Laxity was less than 2 mm in 96.7% of the navigated group (83% in conventional group). The variability of laxity in the navigated group was significantly less than the conventional group, with the standard deviation of the navigated group being smaller than the conventional group standard deviation (p = 0.0003 at 150N and 0.0005 at 200N TELOS).

A significant difference (p=0.03) was found between the groups in the ATB value characterising the sagittal position of the tibial tunnel (negative ATB values imply graft impingement in extension). In the conventional group mean ATB was -1.2 (-5-+4) while it was 0.4 (0 - 3) in Group II. There were no negative ATB values in the Navigated Group.

The use of computer assisted navigation creates a more consistently accurate tibial tunnel position than using conventional techniques. It is suggested that this should reduce impingement and improve graft longevity.