Synthes Inc., the world's No. 3 manufacturer of spinal-implant devices, said today U.S. regulators approved its back-disc replacement product.

Synthes, with worldwide headquarters in West Chester, said the U.S. Food and Drug Administration has approved ProDisc-C total disc replacement to sell in the United States.

The product, an implant that replaces a diseased disc, is already marketed in Europe and other countries.

Synthes, which makes instruments, implants and biomaterials for spinal disorders, employs about 1,400 in several Chester County locations, including Brandywine, Paoli and West Chester. The company ranks third behind Medtronic Inc. and Johnson & Johnson in the $5.5 billion spinal-implant market. Synthes has 8,770 employees worldwide. European headquarters are in Solothurn, Switzerland.