Is viewing the femoral footprint end on while drilling the femoral tunnel in an ACL reconstruction more accurate ?
Authors: Mhaskar Vikram , Maheshwari Jitendra , Singh Ajay , Soni Pankaj 
Published: September 2020

Introduction:

Arthroscopic transportal ACL reconstruction traditionally involves viewing from the anterolateral portal and working from a portal on the medial side. This involves seeing the notch from the same side which evades an end on view of the whole lateral notch. Viewing from the medial side gives an end on view of the same. Working and viewing from the same side may create overcrowding of instruments. We overcame this by using a low far medial portal for drilling and viewing with a high anteromedial portal. We compared both techniques using 3D CT scans to analyse whether there was any difference in intended tunnel placements.

Hypotheses:

Viewing and working from the medial side would give a different tunnel position from viewing from the lateral and working from the medial portal.

Methods:

60 patients were recruited , equal numbers underwent transportal ACL reconstruction using semitendinosus and gracilis grafts by Technique A (Viewing from a high anterolateral portal just next to the patellar tendon at the level of the inferior pole of the patella and working from a low far medial portal) and Technique B (Viewing from high medial portal at the level of inferior pole of patella just next to the patellar tendon and working from a low far medial portal). Tunnels were made leaving 5 mm of back wall and just above the equator of the lateral aspect of the notch. 3 D CT scans were done 3 weeks after the surgery and location of the tunnels were studied using A modification of Edwards technique described by P Lertwanich et al,. A rectangle is drawn connecting the highest point of the lateral wall of the notch anteriorly, lowest point inferiorly, anterior and posterior most aspect after digitally subtracting the medial femoral condyle to expose the lateral aspect of notch. The footprint was covered by the best fit circle on a software, that covered all borders of the femoral tunnel. Centre of this circle was marked and perpendiculars bisecting it from the length and breadth of the rectangle were drawn. The centre of the femoral tunnel was expressed as a percentage from anterior and posterior.

Results:

60 knees were evaluated 52 right (Technique A: 27 and Technique B: 25) and 8 left knees ( Technique A :3 and Technique B:5 ). The mean age of the patients was 27.3 yrs ( Technique A : 26.7 yrs (Range 19-41yrs) and Technique B 27.6 yrs (Range 18-43yrs). There were 41 male and 19 female patients ( Technique A 18 males and 12 females, Technique B had 23 males and 7 females). Mean graft diameter was 8.8mm (range 7-10) in technique A and 8.6mm (range 8-10) in Technique B. MDS (Mean distance from superior margin)Technique A : 35.28 , Standard deviation (SD)6.7339, Technique B MDS 35.86, Standrad deviation9.4441 Mean Distance from posterior margin (DP) :Technique A 35.83 ,SD:8.2008, Technique B 38.14 SD: 8.6991 The t value for DS calculated is 0.2767, the P value is 0.7830 confidence interval is (-4.825, 3.653) . The t value for DP calculated is 1.060, the p value is 0.2937 confidence interval is (-6.682, 2.056) We concluded after applying the independent student t test that the p value is greater than 0.05. So mean distance of femoral tunnel from superior, posterior border in technique A does not differ significantly from mean distance of femoral tunnel from superior border, posterior border in technique B

Conclusion:

An end on view while making the femoral tunnel does not give any added benefit in accuracy of femoral tunnel placement in this study.