SpinalMotion has completed the fourth and final round of a $15.1 million debt offering, according to a MassDevice report.

SpinalMotion is a Mountain View, Calif.-based developer of spine artificial discs that manufactures the Kineflex line of cervical disc implants, which includes the Kineflex Disc (lumbar) and the Kineflex|C Disc (cervical).

The $15.1 million raised came from 15 unnamed investors.