Assessment of correlation between knee notch width index and the three-dimensional notch volume

This study was done to determine whether there is a correlation between the notch volume and the notch width index (NWI) as measured on the three most frequently used radiographic views: the Holmblad 45°, Holmblad 70°, and Rosenberg view. The notch volume of 20 cadaveric knees was measured using Computed Tomography (CT). The Holmblad 45°, Holmblad 70°, and Rosenberg notch view radiographs were digitally re-created from the CT scans for each specimen, and the NWI was measured by two observers. The Pearson correlation coefficient between the NWI and notch volume was calculated, as well as between the three views. An independent t test was performed to determine the difference in NWI and notch volume between male and female specimens. The reliability for each view was also determined. There was no correlation between the NWI as measured on the Holmblad 45°, Holmblad 70°, or Rosenberg view and the notch volume. All three radiographic views proved reliable, but showed only a moderate correlation with each other. Men had larger notch volumes than women, but there was no difference in NWI. A knee with a small intercondylar notch is often considered an increased risk for ACL rupture. The NWI is a frequently used two-dimensional method to determine notch size. However, in the present study, this index was not positively correlated with the overall volume of the notch. Based on the results of the current study, the authors would advice to use caution when using notch view radiographs in a clinical setting to predict risk of ACL rupture.