Fig. 1.

Linear rim penetration was increased for retrieved Charité total disc replacement components exhibiting severe impingement. Provided are boxed ranges of the 25th to 75th percentile and whiskers showing the 1st and 4th quartiles. The length of the whiskers is equal to 1.5 times the box height; anything outside of this range is considered an outlier and is shown as an open circle. Representative images are also provided to illustrate both impingement classifications. A significant difference between impingement groups was determined with use of independent t tests.