ICD-10-CM · Spine

M99.31

Narrowing of the spinal neural canal in the cervical region caused by bony changes — including osteophytes, hypertrophied facets, or ossified ligaments — that encroach on the canal space.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 11
Region: Spine

Drawn from CDCICD10DataAAPCIcdcodes

Documentation tips

What should appear in the chart to support M99.31.

Source · Editorial brief grounded in 5 cited references ↓

Specify the imaging modality and cervical level(s) affected (e.g., 'CT confirms osteophytic encroachment at C5-C6 with canal narrowing').
Use language that names the bony structure causing stenosis — osteophytes, ossified posterior longitudinal ligament (OPLL), hypertrophied facet joints — to justify osseous over connective tissue or disc etiology.
Document the primary diagnosis (e.g., M48.02 cervical spinal stenosis) separately; M99.31 supports it as the bony mechanism, not as a standalone primary code.
Record neurological findings such as myelopathy signs, radiculopathy, upper extremity weakness, or gait disturbance that establish clinical correlation with imaging stenosis.
Note whether the cervicothoracic junction is involved, since that maps to M99.31 per the ICD-10-CM index — clarifying this prevents the coder from hunting a non-existent separate code.

Related CPT procedures

Procedure codes commonly billed with M99.31. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

22551 $1,604.91

Anterior cervical discectomy and fusion (ACDF) at a single interspace, performed through a front-of-neck approach with removal of disc material and arthrodesis of adjacent vertebral bodies.

22554 $1,215.79

Anterior interbody arthrodesis of the cervical spine below C2, performed via anterior approach with minimal diskectomy to prepare the interspace for fusion — not performed for decompression purposes.

22600 $1,282.93

Posterior or posterolateral cervical spinal fusion at a single interspace below C2, performed through a posterior approach to achieve bony arthrodesis.

63015 $1,444.59

Cervical laminectomy spanning more than two vertebral segments for spinal cord or cauda equina exploration and/or decompression, performed without facetectomy, foraminotomy, or discectomy.

63045 $1,249.53

Open cervical laminectomy with facetectomy and foraminotomy at a single vertebral level to decompress nerve roots or the spinal cord.

63048 $187.38

Add-on code for laminectomy, facetectomy, and foraminotomy at each additional cervical, thoracic, or lumbar vertebral segment beyond the primary segment.

72141 $190.72

MRI of the cervical spinal canal and its contents performed without contrast material.

99213 $95.19

Established patient office or outpatient visit requiring 20–29 minutes of total time or low-complexity medical decision-making.

99214 $135.61

Office visit for an established patient requiring moderate-complexity medical decision making (MDM), or 30–39 minutes of total provider time on the date of service.

72156 View procedure details

72325 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M99.31 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Assigning M99.31 as the sole or primary diagnosis violates the M99 tabular note — always pair it with a classifiable primary code (e.g., M48.02) when one exists.
Conflating osseous canal stenosis (M99.31) with foraminal stenosis (M99.61); the neural canal and the intervertebral foramina are distinct anatomical spaces requiring different codes.
Using M99.31 when the documented mechanism is disc herniation or ligamentous hypertrophy without bony involvement — those map to M99.51 (disc) or M99.41 (connective tissue), respectively.
Defaulting to M99.39 (abdomen and other regions) or the nonspecific parent M99.3 when cervical-region documentation is present; M99.31 is the correct billable code for cervical and cervicothoracic stenosis.
Omitting M99.31 from claims where bone spurs are explicitly identified on imaging as contributing to canal narrowing, leaving the bony etiology undocumented and potentially undercoding the clinical picture.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M99.31 captures osseous (bone-driven) stenosis of the neural canal specifically at the cervical level. Use it when imaging — MRI, CT, or plain film — confirms that bony structures are the primary source of canal narrowing at C1–C7 or the cervicothoracic junction. The index entry for 'cervicothoracic' also maps to M99.31, so this code covers both pure cervical and cervicothoracic presentations.

M99.31 lives under M99 (Biomechanical lesions, not elsewhere classified), which carries a critical tabular note: do not assign any M99 code if the condition can be classified elsewhere. In practice, this means M99.31 functions best as a supplemental or contributing-cause code alongside a primary structural diagnosis such as M48.02 (spinal stenosis, cervical region) or a cervical disc disorder from M50.–. It pinpoints the bony mechanism when documentation and imaging support it.

Do not confuse M99.31 with adjacent codes: M99.61 covers osseous and subluxation stenosis of the intervertebral foramina (a different anatomical space), M99.41 covers connective tissue stenosis of the neural canal at the cervical level, and M99.51 targets intervertebral disc stenosis of the same canal. If multiple mechanisms are documented — bone spurs plus disc herniation, for example — code each contributing type separately.

Sibling codes

Other billable codes under M99.3 (laterality / anatomic variants).

M99.39

Osseous stenosis of neural canal of abdomen and oth regions

M99.35

Osseous stenosis of neural canal of pelvic region

M99.30

Osseous stenosis of neural canal of head region

M99.37

Osseous stenosis of neural canal of upper extremity

M99.33

Osseous stenosis of neural canal of lumbar region

M99.32

Osseous stenosis of neural canal of thoracic region

M99.38

Osseous stenosis of neural canal of rib cage

M99.34

Osseous stenosis of neural canal of sacral region

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01Can M99.31 be used as a primary diagnosis on a claim?

Generally no. The M99 category note instructs coders not to use these codes when the condition can be classified elsewhere. Assign a primary code such as M48.02 (cervical spinal stenosis) first, then add M99.31 to specify the osseous mechanism.

02Does M99.31 cover the cervicothoracic junction, or only pure cervical levels?

Both. The ICD-10-CM alphabetic index maps 'cervicothoracic' osseous neural canal stenosis to M99.31, so one code handles C1–C7 and the cervicothoracic transition.

03What is the difference between M99.31 and M99.61?

M99.31 describes osseous stenosis of the neural canal (the central spinal canal), while M99.61 describes osseous and subluxation stenosis of the intervertebral foramina — the lateral exit points for nerve roots. Imaging findings determine which anatomical space is narrowed.

04When should I use M99.31 versus M99.41 or M99.51?

Use M99.31 when bone (osteophytes, ossified ligament, hypertrophied facets) is the documented cause of canal narrowing. Use M99.41 for connective tissue causes (ligamentum flavum hypertrophy without ossification) and M99.51 when intervertebral disc protrusion drives the stenosis. Multiple codes may apply if imaging documents more than one mechanism.

05What imaging documentation best supports M99.31?

CT or MRI reports that explicitly identify bony encroachment — osteophyte formation, ossified posterior longitudinal ligament, or facet hypertrophy — at a named cervical level provide the strongest support. A Kellgren-Lawrence grade or canal diameter measurement strengthens medical necessity.

06Is M99.31 appropriate for chiropractic or physiatry billing, or only surgical claims?

It is appropriate across specialties whenever bony cervical canal stenosis is documented. Chiropractors, physiatrists, neurologists, and spine surgeons can all use it as long as the underlying diagnosis supports the M99 category and the primary condition is coded first.

07How does M99.31 relate to OPLL (ossified posterior longitudinal ligament)?

OPLL is a specific cause of osseous neural canal stenosis. If the provider documents OPLL and it is narrowing the cervical canal, M99.31 is an appropriate supporting code alongside the primary diagnosis. Document the OPLL explicitly in the impression or assessment to justify it.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M99-M99/M99-/M99.31
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M99.31
04
icdcodes.ai
https://icdcodes.ai/diagnosis/cervical-spine-stenosis/documentation
05
icdcodes.ai
https://icdcodes.ai/diagnosis/cervical-stenosis/documentation

Mira AI Scribe

The Mira AI Scribe captures the imaging modality, specific cervical level(s), and bony structure identified (osteophytes, OPLL, hypertrophied facets), plus any neurological findings such as myelopathy or radiculopathy. This prevents the code from being dropped to the nonspecific parent M99.3 or misassigned to a connective tissue or disc stenosis code, and it establishes the medical necessity linkage between osseous findings and the patient's clinical presentation.

See how Mira captures M99.31 documentation