Abstract
Hypothesis
Recent advances in understanding of ACL insertional anatomy has led to new concepts of anatomical positioning of tunnels for ACL reconstruction. Femoral tunnel position has been defined in terms of the lateral intercondylar ridge and the bifurcate ridge but these can be difficult to identify at surgery. Measurements of the lateral wall either using C-arm x-ray control or specific arthroscopic rulers have also been advocated.
Method
30 patients undergoing ACL reconstruction before and after introduction of a new anatomical technique of ACL reconstruction were evaluated using 3D CT scan imaging with cut away views of the lateral aspect of the femoral notch and the radiological quadrant grid. In the new technique, with the knee at 90 degrees flexion, the femoral tunnel was centred 50% from deep to shallow as seen from the medial portal (Group A). Group B consisted of patients where the femoral tunnel was drilled through the antero-medial portal and offset from the posterior wall using a 5mm jig.
Results
Ridges were identifiable in only 76% of scans. All tunnels in Group A (anatomical technique) were found to be below (posterior to) the lateral intercondylar (residents) ridge and were within 10% of the optimal position as defined by the Grid method on x-ray. No femoral tunnels in Group B meet anatomical criteria and were malpositioned by a mean of 5mm.
Conclusion
We believe 3D CT scan imaging with cut away views of the femoral tunnel is a useful and accurate way of describing tunnel position, and that this technique will be valuable in validating new surgical techniques. According to this CT scan analysis the new anatomical technique correctly placed the femoral tunnel. This work forms the basis of a subsequent randomised trial of techniques in relation to clinical outcome.
