Summary

The purpose of this study is to evaluate the relationship between the anatomical tunnel position of ACL ,described by the quadrant method in the previous reports, and the shape of the femoral condyle on each knees. Our results indicate that the tunnel position of ACL measured with quadrant method is influenced by the variation of the blumensaat’s line.

Abstract

"Introduction:
Recently, the quadrant method is most popular method to evaluate the tunnel position after ACL reconstruction. The quadrant method uses blumensaat’s line and femoral condyle as a reference to make the axis of coodinates. However, blumensaat’s line and femoral condyle have many variations. Therefore, the quadrant method may be inaccurate to evaluate the position of the bone tunnel on ACL reconstruction.
The purpose of this study is to evaluate the relationship between the anatomical tunnel position of ACL ,described by the quadrant method in the previous reports, and the shape of the femoral condyle on each knees.

Material&Methods
The pre-operative Computed tomography (CT) data was obtained from 40 patients, performed with ACL reconstruction in our University Hospital, between March 2015 and June 2016.
CT data were imported to mimics software (Materialise) to create a 3D model of the distal femur. The distal femur model was positioned horizontally in a true lateral position, in which both femoral condyles were superimposed. The medial femoral condyle was removed at the center of the condyle.
(Evaluation protocol)
1, The anatomical femoral tunnel positions, which reported by Forsythe et al, were plotted on the medial wall of lateral femoral condyle with previously established quadrant method. The grid was aligned with the blumensaat’s line.
2, The 4x4 grid, based on the lateral intercondylar ridge (LIR) and contour of lateral femoral condyle, was described on the medial wall of lateral femoral condyle. The extended line from posterior cortex of femoral condyle was used instead of LIR.
Plotted points were measured using the grid as the percentage distance from intersection point of the extended line from posterior cortex of femoral condyle and the Blumensaat’s line.
3, In addition,a angle and ß angle were measured. Thea angle shall be the angle formed by the long axis of femoral bone and the straight line passing through the center of two bone tunnel, Anteromedial(AM) bundle and Posterolateral(PL) bundle. Theß angle shall be the angle formed by the long axis of femoral bone and the extended line from posterior cortex of femoral condyle.

Result:
On the new grid, AM tunnel and PL tunnel were measured at 27.5 ± 2.7% and 53.6 ± 3.7%,respectively,(parallel to the posterior cortex of femoral condyle), and29.2 ± 6.2% and 9.6 ± 11.4%,respectively,(perpendicular to the posterior cortex of femoral condyle). As for the angle measurement, a angle and ß angle were 7.2 ± 7.6° and 26.8 ± 3.3°, respectively.

Discussion

In this study, the position of PL bundle has much variability compared with the position of AM bundle. In addition, it is found that the standard deviation of aangle was 7° and the difference between the maximum value ofaangle and the minimum value of aangle was 39°. These results indicate that the tunnel position of ACL measured with quadrant method is influenced by the variation of the blumensaat’s line.
The new evaluation method used LIR will be necessary to know the appropriate tunnel position in the best ACL reconstruction.
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