Reliability of Tunnel Measurements and the Quadrant Method Using Fluoroscopic Radiographs After Anterior Cruciate Ligament Reconstruction

Background: Anterior cruciate ligament (ACL) reconstruction tunnel placement is often evaluated by radiographs. This study ex- amines the interobserver reliability of various radiographic measurements of ACL tunnels.

Hypothesis: When ideal radiographic views are obtained, the interobserver reliability of the measurements among experienced surgeons would be good to excellent.

Study Design: Descriptive laboratory study.

Methods: Tunnels for single-bundle ACL reconstruction were drilled and filled with metal interference screws or a tibial reamer on 73 cadaveric knees. Ideal fluoroscopic radiographs were obtained. Three independent reviewers performed 18 measurements including a modification of the grid method. For the grid method analysis, reviewers fit a 16 3 12 grid to the lateral knee radio- graph, and the center of the femoral tunnel was marked. Interobserver reliability of the measurements was performed using intra- class correlation coefficients (ICCs). A precision grouping analysis was performed for the grid measurements to calculate the mean radius and standard deviation grouping distances.

Results: The ICCs were excellent (..75) for the tibial tunnel angles and tunnel measurements, the clock face measurement, and the Aglietti et al and Jonsson et al measurements. The ICCs were good (.4-.75) for an estimation of graft impingement, Harner et al measurements, and notch height. The mean radius for grid measurements was 0.6 6 0.4 units (range, 0-2.36 units), with each unit being 1 box in the 16 3 12 grid. When a circle was constructed with a 1.3-unit radius, 95% of the 3 surgeons’ measurements would be included in the area of that circle.

Conclusion: Reliability of ACL tunnel measurements was good to excellent under ideal circumstances for the majority of meas- urements. The modified grid method demonstrated very acceptable reliability.

Clinical Relevance: Measurements with good to excellent reliability can be used to evaluate ACL tunnel placement when ideal radiographic views are obtained.

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