Method of fixing a spine with a fixation plate

A method of fixing a spine with a fixation plate assembly, comprising the steps of:

• providing a fixation plate assembly comprising:
• a fixation plate having an upper surface, a lower surface, and at least two apertures therethrough, each of the apertures having at least one internal annular recess disposed in at least one of said upper surface and said lower surface;
• at least two inserts flexibly retained within the apertures, each of the inserts comprising a threaded axial throughbore and at least one flange, the at least one flange being configured for mating engagement within the at least one internal annular recess;
• and
• at least two bone screws, each of the bone screws comprising a threaded portion configured for threading engagement with the threaded axial throughbore of the inserts;
• placing the fixation plate against at least a pair of vertebrae so as to align one of the at least two apertures over one vertebra and another of the at least two apertures over another vertebra;
• inserting each of the at least two bone screws through each of the at least two inserts, respectively, and into the vertebrae;
• and
• locking the bone screws within the inserts while maintaining flexibility between the inserts and the plate, the bone screws being locked within the inserts by threadably engaging the threaded portion of the bone screws with the threaded axial throughbore of the inserts;
• and
• allowing movement between the vertebrae while maintaining the plate in a fixed condition relative to the vertebrae.