Posterior shoulder arthroplasty implants, systems, and methods

A stemless humeral head replacement system comprising:

• a base plate comprising a bone facing side, an implant side opposite the bone facing side, a curvate perimeter, an implant engagement structure on the implant side, and at least one fin protruding from the bone facing side a first distance and extending linearly a length between side edges of the curvate perimeter;
• and
• a humeral head implant comprising a curvate implant surface and a base plate engagement structure opposite the curvate implant surface, the base plate engagement structure configured to couple to the implant engagement structure of the base plate;
• and
• a reference guide and a guide pin, the reference guide comprising a targeting arm having a curvate arm configured to be positioned around a spherical bone and terminating at a blunt tip, and a sleeve having a guide hole that is configured to guide the guide pin through the spherical bone to the blunt tip.

A stemless humeral head replacement system comprising:

• a base plate comprising a bone facing side, an implant side opposite the bone facing side, a curvate perimeter, an implant engagement structure on the implant side, and at least one fin protruding from the bone facing side a first distance and extending linearly a length between side edges of the curvate perimeter;
• and
• a humeral head implant comprising a curvate implant surface and a base plate engagement structure opposite the curvate implant surface, the base plate engagement structure configured to couple to the implant engagement structure of the base plate;
• and
• a base plate delivery tool comprising an first engagement structure comprising a first pair of tips at a distal end and a first handle at a proximal end, each of the first pair of tips including a first protrusion configured to engage a portion of the base plate, the first engagement structure including a curvate flange configured to abut the curvate perimeter of the base plate when coupled thereto, the first engagement structure further including a bone engagement flange protruding beyond the curvate flange and configured to engage a bone portion when sliding the base plate onto a resected bone surface.