Figure 1

Classification of the extension direction of each pair of osteophytes across the intervertebral disc space. Group A: no osteophytes. Group B: the pair of osteophytes extended in the direction of the adjacent disc. Group C: almost complete bone bridge formation by a pair of osteophytes across the intervertebral disc space. Group D: the pair of osteophytes extended in a direction away from the adjacent disc. Group E: the osteophytes extended nearly horizontally to the vertebral body border without closing the intervertebral disc space. Group F: ungroupable