M46.21 — Osteomyelitis of vertebra, occipito-atlanto-axial region

BillableCC

Is M46.21 billable?

Yes — M46.21 is billable for FY2027. M46.21 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. M46.21 may be submitted for encounters from October 1, 2026 through September 30, 2027.

M46.21 at a glance

Code	M46.21
Description	Osteomyelitis of vertebra, occipito-atlanto-axial region
Billable	Yes
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027

Which MS-DRGs does M46.21 group to?

M46.21 sits in MDC 08 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.

456Spinal Fusion Except Cervical with Spinal Curvature, Malignancy, or Infection with MCCsurgical
457Spinal Fusion Except Cervical with Spinal Curvature, Malignancy, or Infection with CCsurgical
458Spinal Fusion Except Cervical with Spinal Curvature, Malignancy, or Infection without CC/MCCsurgical

As a secondary diagnosis, M46.21 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.

How is M46.21 listed in the Alphabetic Index?

These are the routes through the Alphabetic Index that lead to M46.21. They show the wording a clinician may have documented, which often differs from the Tabular description.

Osteomyelitis › vertebra › occipito-atlanto-axial region (general) (infective) (localized) (neonatal) (purulent) (septic) (staphylococcal) (streptococcal) (suppurative) (with periostitis)

Excludes2 — not included here — inherited from Chapter 13

The conditions below are not part of M46.21, but a patient may have both at the same time. When documentation supports it, M46.21 and the excluded code may both be reported.

arthropathic psoriasis (L40.5-)
certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
compartment syndrome (traumatic) (T79.A-)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

How long has M46.21 existed?

M46.21 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.

Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.

Which conditions are coded to M46.21?

ICD-10 code for Osteomyelitis