Sagittal femoral condyle morphology correlates with femoral tunnel length in anatomical single bundle ACL reconstruction

Purpose The purpose of this study was to reveal the correlation between femoral tunnel length and the morphology of the femoral intercondylar notch in anatomical single bundle anterior cruciate ligament (ACL) reconstruction using three-dimensional computed tomography (3D-CT). Methods Thirty subjects undergoing anatomical single bundle ACL reconstruction were included in this study (23 female, 7 male: average age 45.5 ± 16.7). In the anatomical single bundle ACL reconstruction, the femoral and tibial tunnels were created close to the antero-medial bundle insertion site with trans-portal technique. Using post-operative three-dimensional computed tomography (3D-CT), accurate axial and lateral views of the femoral condyle were evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the transepicondylar length (TEL), notch width index, notch outlet length, the notch area (axial), length of Blumensaat’s line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analyzed. Tunnel placement was also evaluated using a Quadrant method. Results The average femoral tunnel length was 35.4 ± 4.4 mm. The average TEL, NWI, notch outlet length, and the axial notch area, were 76.9 ± 5.1 mm, 29.1 ± 3.8%, 19.5 ± 3.9 mm, and 257.4 ± 77.4 mm 2 , respectively. The length of Blumensaat’s line and the height and area of the lateral wall of the femoral intercondylar notch were 33.8 ± 3.2 mm, 22.8 ± 2.3 mm, and 738.7 ± 129 mm 2 , respectively. The length of Blumensaat’s line, the height, and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 23.4 ± 4.5% in a shallow-deep direction and 35.4 ± 8.8% in a high-low direction. Conclusion The length of Blumensaat’s line, height, and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single bundle ACL reconstruction. For clinical relevance, these parameters are useful in predicting the length of the femoral tunnel in anatomical single bundle ACL reconstruction for the prevention of extremely short femoral tunnel creation. Level of evidence Case controlled study, Level III.