The following supplementary subclassification to indicate the site of involvement is provided for optional use with appropriate categories in the block on dorsopathies, except categories M50 and M51; see also note on page 628
0 Multiple sites in spine
1 Occipito-atlanto-axial region
2 Cervical region
3 Cervicothoracic region
4 Thoracic region
5 Thoracolumbar region
6 Lumbar region
7 Lumbosacral region
8 Sacral and sacrococcygeal region
9 Site unspecified