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.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 16
- Region
- Spine
Documentation tips
What should appear in the chart to support M43.22.
Source · Editorial brief grounded in 5 cited references ↓
- Specify the exact cervical levels involved in the fusion (e.g., C4–C5, C5–C6) — level-specific documentation directly supports medical necessity for any associated surgical or imaging CPT codes.
- Distinguish acquired cervical fusion (M43.22) from surgical arthrodesis status (Z98.1) in the medical record; if a prior ACDF is on file, clarify whether the current fusion finding is at a new level or represents pathological extension.
- Document imaging findings explicitly — CT or MRI evidence of bony ankylosis, loss of disc space, or bridging osteophytes confirms the diagnosis and protects against audit challenge.
- Exclude ankylosing spondylitis, Klippel-Feil syndrome, and congenital cervical fusion in the clinical note before assigning M43.22; these have their own codes and M43.2 carries Type 1 Excludes for them.
- If adjacent segment degeneration is the driver of the encounter, code that condition as primary and list M43.22 as secondary context — document the clinical relationship between the two findings.
Related CPT procedures
Procedure codes commonly billed with M43.22. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M43.22 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Assigning M43.22 for a patient who simply had a prior cervical fusion surgery — that is arthrodesis status, coded Z98.1, not M43.22.
- Using M43.22 when cervical fusion is due to ankylosing spondylitis; M45.0– is the correct category and M43.2 has a Type 1 Excludes note for ankylosing spondylitis.
- Defaulting to M43.20 (site unspecified) instead of M43.22 when cervical involvement is clearly documented — always assign the most specific code supported by documentation.
- Confusing M43.22 (cervical) with M43.23 (cervicothoracic) — when fusion spans the cervicothoracic junction, use M43.23, not M43.22.
- Failing to add Z98.1 as a secondary code when the patient has both a history of surgical arthrodesis at one level and documented pathological fusion at another — both may be clinically present and codeable simultaneously.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
M43.22 applies when the cervical spine has undergone acquired fusion — meaning the vertebral joints have become pathologically ankylosed — and the fusion is neither congenital nor the result of a deliberate surgical arthrodesis procedure. This code sits under the M43.2 (Fusion of spine) parent and is the cervical-region-specific child code. Use it when clinical or imaging documentation confirms cervical spinal ankylosis not attributable to ankylosing spondylitis (M45.0–), congenital fusion (Q76.4), or Klippel-Feil syndrome (Q76.1), all of which are Type 1 Excludes under M43.2.
A critical distinction for spine coders: M43.22 is NOT the code for a patient's prior surgical cervical fusion. Post-operative arthrodesis status is captured with Z98.1 (Arthrodesis status). M43.22 describes the pathological finding of cervical spinal fusion as a diagnosis — most commonly documented on imaging as bony ankylosis of facet joints or disc spaces in degenerative or inflammatory contexts where another specific etiology (e.g., ankylosing spondylitis) has been excluded.
When coding adjacent segment disease following prior cervical fusion, M43.22 may appear as a secondary or contextual diagnosis alongside the primary pathology driving the current encounter. Document the specific cervical levels involved and the nature of the fusion (e.g., spontaneous bony bridging vs. prior surgical level now excluded from Z98.1 scope) to support medical necessity and withstand payer audit.
Sibling codes
Other billable codes under M43.2 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01Is M43.22 the right code after a patient has had an anterior cervical discectomy and fusion (ACDF)?
02What is the difference between M43.22 and M43.23?
03Can M43.22 and Z98.1 be coded together on the same claim?
04Does ankylosing spondylitis causing cervical fusion map to M43.22?
05Is Klippel-Feil syndrome coded as M43.22?
06What imaging findings support M43.22 in the documentation?
07Which CPT procedures are most commonly billed with M43.22?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M40-M43/M43-/M43.22
- 03icdcodes.aihttps://icdcodes.ai/diagnosis/fusion-of-spine/documentation
- 04cms.govhttps://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=59674&ver=15
- 05cms.govhttps://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=59668&ver=21
Mira AI Scribe
Mira captures the cervical levels affected, imaging confirmation of bony ankylosis or joint fusion, the absence of ankylosing spondylitis or congenital etiology, and any prior surgical arthrodesis history — distinguishing pathological fusion (M43.22) from arthrodesis status (Z98.1). Precise capture prevents unspecified-site downcoding to M43.20 and flags the excludes-note conflicts that trigger claim denials.
See how Mira captures M43.22 documentation