The ‘‘line of initial erosion’’ or ‘‘biconcavity demarcation’’ between
the noneroded anterior glenoid surface (paleoglenoid) and
the eroded posterior glenoid surface (neoglenoid) was identified
and measured as points on a clock face to within the closest
30 minutes. In a left shoulder, this line often runs from 1 o’clock
to 7 o’clock. For standardization of data, all right shoulder clockface
measurements were converted to left shoulder clock-face
measurements (Fig. 1). To quantify the extent of posterior erosion,
the glenoid sizer disk was held in intimate contact with the
paleoglenoid. With this held firmly in place, a smooth K-wire or
an arthroscopic measurement probe was then placed alongside the
posterior rim of the disk at the point of maximal neoglenoid
erosion. Depth of erosion was recorded to the nearest millimeter.
Glenoid reaming was initiated. Whereas our goal was 100% bone
support of each component, we were willing to accept