You're right. The first lumbar disc replacement was done in the 1950s. Since then many trials with various different implants have been done. Most of these were put into cadavers or animals, not live humans.
It wasn't until the 1980s that an implant designed for humans was tried. There were concerns about the materials so the implants were never put on the public market. Later new materials were tested in cadavers and monkeys.
More recently surgical tools, techniques, and imaging equipment has made it possible to consider artificial discs once again. The Food and Drug Administration (FDA) approved the first one in 2004 for use in humans. Since then centers all over the United States have implanted hundreds of disc replacements with good results.
Compared to spinal fusion disc replacement has a shorter operative time and fewer days in the hospital. That means reduced costs, which is very popular in the health care world.
Patients have a faster recovery. More people are able to get back to work sooner. And the best benefit of all is restoring normal motion in the spine, making this a very popular treatment alternative to spinal fusion.