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

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Risk adjustment (HCC)

• CMS-HCC V28: HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
• CMS-HCC V22: HCC 39 — Bone/Joint/Muscle Infections/Necrosis
• ESRD V24: HCC 39

MS-DRG index

Defines the logic of DRG(s) 456-458 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 730.28 Unspecified osteomyelitis, other specified sites (approximate)

Code annotations containing back-references to M46.21

Back-references to M46.2

• Type 2 Excludes: M86 Osteomyelitis ("vertebra (M46.2-)")

Back-references to M46

• Type 1 Excludes: G55 Nerve root and plexus compressions in diseases classified elsewhere ("nerve root compression (due to) (in) spondylopathies (M46.-, M48.-)")

Diagnosis Index entries for M46.21

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

Nearby codes

• M46.08 Spinal enthesopathy, sacral and sacrococcygeal region
• M46.09 Spinal enthesopathy, multiple sites in spine
• M46.1 Sacroiliitis, not elsewhere classified
• M46.2 Osteomyelitis of vertebra
• M46.20 Osteomyelitis of vertebra, site unspecified
• M46.21 Osteomyelitis of vertebra, occipito-atlanto-axial region (this code)
• M46.22 Osteomyelitis of vertebra, cervical region
• M46.23 Osteomyelitis of vertebra, cervicothoracic region
• M46.24 Osteomyelitis of vertebra, thoracic region
• M46.25 Osteomyelitis of vertebra, thoracolumbar region
• M46.26 Osteomyelitis of vertebra, lumbar region