Shoulder prosthesis. Coloured X-ray of a prosthetic (artificial) shoulder joint (black, upper left) replacing the end of a bone fractured due to osteoporosis (brittle bone disease). The prosthesis has been cemented into the shaft of the fractured humerus (upper-arm bone, centre left). The shoulder joint is where the humerus meets the scapula (shoulder blade). The clavicle (collarbone) runs from upper centre to far right and the ribs are at lower right. Metal staples (small black loops) have been used to hold together the incision made to insert the implant. Osteoporosis is characterised by weaker bones that are more liable to fracture.