Intervertebral fusion cage implant and surgical procedure therefor

An intervertebral fusion cage implant, comprising:

• the intervertebral fusion case implant being elongate;
• and
• defining superior and inferior bearing surfaces,
• the inferior bearing surface having vertebral body engaging interferences;
• and
• the superior bearing surface having:
• a smooth surface profile;
• sagittal plane convexity, the sagittal plane convexity defining a sagittal plane axis rising anteriorly with respect to a horizontal sagittal plane axis;
• and
• sagittal plane curvature asymmetry, wherein:
• the superior bearing surface defines a central section having coronal plane convexity and
• lateral sections adjacent the central section and wherein the implant is sized so that the central section bears against a central endplate of an adjacent vertebra in use and the lateral sections bear against opposite sides of an epiphyseal rim of the adjacent vertebra in use.