The ornamental design for a therapeutic neckdevice, as shown and described.
FIG. 1 is a front perspective view of a therapeutic neck device, showing my new design;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a front elevation view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a rear elevation view thereof; and,
FIG. 8 is a section view of FIG. 6, taken along line 8-8.
The broken lines showing the D-rings depict portions of the therapeutic neck device that form no part of the claimed design, while the remaining broken lines shown in the drawings depict the bounds of the claimed design.