First milling
Insert the 0 spigot [36], which has the thickest collar, into the large drill hole and tap until the collar abuts the bone (Fig. 7.17). This ensures that the dual reference at the bottom of the hole and on the surface of the condyle are aligned.
Figure 7.17
By extending the knee slightly and retracting the soft tissues, manoeuvre the spherical mill [43] onto the spigot (Fig. 7.18(a)) and into the wound so that the teeth touch the bone (Fig. 7.18(b)). Take care to avoid trapping soft tissues.
Figure 7.18(a)
Figure 7.18(b)
When milling, push firmly in the direction of the spigot axis, taking care not to tilt the mill as this will damage the hole. Mill until the cutter will no longer advance and the spigot can be seen, in the window, to have reached its end stop (see Fig. 6.9). If in doubt, continue to mill; the mill cannot continue beyond the amount permitted by the collar of the selected spigot.
Remove the mill and the spigot and trim off the bone protruding from the posterior corners of the condyle that lie outside the periphery of the cutting teeth (Fig. 7.19). These corners should be removed tangentially to the spherically milled surface with a half inch (12 mm) chisel, taking care not to damage the flat posterior surface of the femoral condyle. In addition, any retained posteromedial osteophytes on the femur should be removed.
