A modular humeral hemiarthroplasty utilizing a prosthesis with a taper-lock design was performed on a 77-year-old woman with a diagnosis of rotator cuff arthropathy. Radiographic examination at 3 months after surgery revealed disarticulation of the modular head and neck from the humeral prosthetic stem. This is a case report of a disarticulated modular humeral hemiarthroplasty.