ARTIFICIAL LIMBS; HIP, KNEE, OR ELBOW PROSTHESES; IMPLANTS FOR MEDICAL PURPOSES COMPRISING ARTIFICIAL MATERIAL; ARTIFICIAL JOINTS AND PARTS THEREOF; CHRIURGICAL AND MEDICAL INSTRUMENTS FOR IMPLANTING AND EXTRACTING HIP, KNEE AND ELBOW PROSTHESES; FIXATION AND POSITIONING DEVICES, NAMELY BONE NAILS AND BONE SCREWS FOR IMPLANTING SUCH PROTHESES