The ornamental design for a medical pillowcover, as shown and described.
FIG. 1 is a top view of a medical pillow cover;
FIG. 2 is a bottom view thereof;
FIG. 3 is a first side view thereof;
FIG. 4 is a second side view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof; and,
FIG. 7 is a perspective view thereof.
The circle-dotted pattern illustrated in FIG. 2 represents a grip texture on the medical pillow cover forming part of the claimed design. The broken lines illustrated in FIG. 3 and FIG. 7 represent stitching and form part of the claimed design.