Fusion of spine

M43.20 identifies ankylosis of a spinal joint where the specific vertebral region has not been documented. It is the least-specific code in the M43.2 family and should be replaced with a site-specific code whenever the affected region is known.

Acquired ankylosis of the spinal joints spanning the occiput, atlas (C1), and axis (C2), resulting in loss of segmental motion at the craniocervical junction — coded when the fusion is a disease process, not a surgical or congenital state.

M43.22 identifies acquired fusion of the cervical spine (C1–C7 region), representing pathological or post-surgical ankylosis of spinal joints in the neck — distinct from congenital cervical fusion and from surgical arthrodesis status.

Spinal fusion or ankylosis affecting the cervicothoracic junction — the transitional segment spanning the lower cervical and upper thoracic vertebrae (typically C7–T1).

Acquired fusion of the thoracic vertebral segment(s), resulting in loss of segmental mobility at the mid-spine level — distinct from surgical arthrodesis status and congenital spinal fusion.

M43.25 identifies an acquired or developmental fusion of the spine at the thoracolumbar junction — the transitional zone where the thoracic spine meets the lumbar spine, typically at the T12-L1 level.

M43.26 identifies ankylosis or pathological fusion of the lumbar spinal joints, representing a fixed, non-mobile state of one or more lumbar vertebral articulations due to disease or prior surgical intervention.

M43.27 identifies ankylosis or pathological fusion of the spine specifically at the lumbosacral region — the junction between the fifth lumbar vertebra and the sacrum — as a disease process, not a surgical procedure status.

M43.28 identifies pathological or acquired ankylosis (bony fusion) of the spinal joints within the sacral and sacrococcygeal region, distinguishing it from surgical arthrodesis status and congenital spinal fusion.