A stemless humeral anchor, comprising: a first end configured to be embedded in a proximal portion of a humerus and a second end opposite the first end; a mating portion comprising a central recess extending from the second end toward the first end, wherein the central recess is configured to receive a corresponding mating portion of an articular component of a humeral assembly; a collar disposed at the second end around the mating portion and extending generally transverse to a longitudinal axis of the recess; and a plurality of rotation control features (22, 22A) disposed between the collar and the first end, wherein the rotation control features are configured to resist rotation of the stemless humeral anchor when the stemless humeral anchor is implanted; the stemless humeral anchor characterized in comprising a void filling protrusion disposed between the collar and the first end of the anchor, wherein the void filling protrusion: is configured as a structure protruding and extending from one of the plurality of rotation control features toward a neighboring second one of the plurality of rotation control features, wherein the void filling protrusion is contiguous with said one of the plurality of rotation control features; or is configured as a radial protrusion from the mating portion and spaced apart from the rotation control features; wherein at least a portion of the stemless humeral anchor is adapted for a specific patient based upon pre-operative imaging. a first end configured to be embedded in a proximal portion of a humerus and a second end opposite the first end; a mating portion comprising a central recess extending from the second end toward the first end, wherein the central recess is configured to receive a corresponding mating portion of an articular component of a humeral assembly; a collar disposed at the second end around the mating portion and extending generally transverse to a longitudinal axis of the recess; and a plurality of rotation control features (22, 22A) disposed between the collar and the first end, wherein the rotation control features are configured to resist rotation of the stemless humeral anchor when the stemless humeral anchor is implanted; the stemless humeral anchor characterized in comprising a void filling protrusion disposed between the collar and the first end of the anchor, wherein the void filling protrusion: is configured as a structure protruding and extending from one of the plurality of rotation control features toward a neighboring second one of the plurality of rotation control features, wherein the void filling protrusion is contiguous with said one of the plurality of rotation control features; or is configured as a radial protrusion from the mating portion and spaced apart from the rotation control features; is configured as a structure protruding and extending from one of the plurality of rotation control features toward a neighboring second one of the plurality of rotation control features, wherein the void filling protrusion is contiguous with said one of the plurality of rotation control features; or is configured as a radial protrusion from the mating portion and spaced apart from the rotation control features; wherein at least a portion of the stemless humeral anchor is adapted for a specific patient based upon pre-operative imaging.