Shoulder prosthesis. Coloured X-ray of a prosthetic (artificial) shoulder joint (black, upper left). The prosthesis has been cemented into the shaft of the humerus (upper-arm bone, centre left), to replace the fractured end of the bone. 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. This fracture was caused by osteoporosis (brittle bone disease), a condition characterised by weaker bones.