Spondylolysis localized to the cervicothoracic junction (C7-T1 transition zone), representing a defect or stress fracture of the vertebral pars interarticularis at that spinal segment.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 10
- Region
- Spine
Documentation tips
What should appear in the chart to support M43.03.
Source · Editorial brief grounded in 4 cited references ↓
- Specify 'cervicothoracic region' or the exact level (C7-T1) in the assessment — generic 'cervical spondylolysis' maps to M43.02, not M43.03.
- Record imaging modality and findings: CT is the gold standard for pars defect visualization; note whether the defect is unilateral or bilateral and if there is any associated listhesis.
- Document symptom duration, neurological findings, and prior conservative treatment to support medical necessity if surgical intervention is planned.
- If spondylolisthesis is also present at the same level, document both conditions explicitly so M43.13 can be coded alongside M43.03.
- Distinguish acquired versus congenital etiology when possible — both fall under M43.03, but the clinical distinction may affect surgical planning documentation.
Related CPT procedures
Procedure codes commonly billed with M43.03. 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 M43.03 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Confusing spondylolysis (M43.03, pars defect) with spondylolisthesis (M43.13, vertebral slip) — they are separate codes even when both coexist at the cervicothoracic level.
- Defaulting to M43.00 (site unspecified) when the operative or radiology report clearly identifies the cervicothoracic junction — always code to the highest specificity supported by documentation.
- Using M43.02 (cervical region) instead of M43.03 when the defect is at the C7-T1 transition — the cervicothoracic region is its own distinct site in the ICD-10-CM hierarchy.
- Omitting radiculopathy or myelopathy codes when neurological compromise is documented — M43.03 alone does not convey the full clinical picture required for surgical authorization.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
M43.03 is the billable code for spondylolysis specifically at the cervicothoracic region — the junction between the cervical and thoracic spine, generally involving C7 or T1. Spondylolysis at this level is far less common than lumbar spondylolysis, so documentation precision matters: the diagnosis must reflect imaging-confirmed pars defect or structural bony defect at the cervicothoracic junction, not merely degenerative change or instability.
Use M43.03 when the provider documents cervicothoracic spondylolysis as acquired or congenital. Approximate synonyms accepted under this code include 'acquired cervicothoracic spondylolysis' and 'cervicothoracic spondylolysis.' Do not conflate this with spondylolisthesis (M43.13) — spondylolysis is the pars defect itself; spondylolisthesis is vertebral slippage, which may or may not coexist. If both are documented at the cervicothoracic level, assign both codes.
This code maps to MS-DRG 551 (Medical back problems with MCC) or 552 (Medical back problems without MCC) under DRG v43.0. It is not listed as a standalone supporting diagnosis on the CMS cervical fusion LCD (A59668), so if fusion is planned, verify that the primary indication code — and any instability or radiculopathy codes — are also present on the claim.
Sibling codes
Other billable codes under M43.0 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What spinal levels does 'cervicothoracic region' cover for M43.03?
02Can M43.03 and M43.13 be coded together?
03Is M43.03 valid as a primary diagnosis for cervical fusion claims?
04Does M43.03 require a 7th character extension?
05What imaging best supports the M43.03 diagnosis?
06How does M43.03 differ from M43.02 and M43.04?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M40-M43/M43-/M43.03
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M43.03
- 04cms.govhttps://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=59668&ver=21&
Mira AI Scribe
Mira AI Scribe captures the spinal region descriptor ('cervicothoracic'), imaging findings (CT or MRI evidence of pars defect at C7-T1), presence or absence of concurrent listhesis, and any neurological findings — preventing a drop to the unspecified M43.00 or a miscapture as cervical-only M43.02, either of which can trigger medical necessity review or claim denial.
See how Mira captures M43.03 documentation