Navigated anterior cruciate ligament replacement: an experimental validation study

We wanted to test the following hypothesis: the location of the tibial and femoral ACL attachments measured by a navigation system differs from their actual anatomic location. A total of 10 gross specimens were studied. The standard navigated procedure was used. Metallic reference pins were implanted around the tibial and femoral ACL attachments and palpated with a navigated stylus. Their position was recorded in comparison with the same tibial or femoral reference point. All measurements were repeated with a caliper. Caliper and navigated measurements were compared with appropriate statistical tests at a 0.05 level of significance. There was a significant difference between caliper and navigated measurements at the tibia in absolute value (maximal range of 4 mm, mean difference about 2 mm), but the difference ratio was low (about 3%); there was no significant difference between caliper and navigated measurements at the femur. There was a strong correlation and a good agreement between caliper and navigated measurements. It is likely that these differences have few, if any, clinical relevance. We demonstrated that the navigation system used during the present study has the potential to enhance the precision of the intra-operative measurement of the tunnel placement during ACL replacement.