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M46.26 ICD-10-CM Code: Osteomyelitis of vertebra, lumbar region

M46.26 maps to CMS-HCC V28 92 (RAF 0.479). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Spondylopathies (M45-M49)

M46.26

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Osteomyelitis of vertebra, lumbar region

A bone infection affecting the vertebrae in the lower back or lumbar region of the spine.

Buddy the Bee presenting code insight

Buddy Insight

Lumbar vertebral osteomyelitis is a serious infection that can cause significant functional disability and neurological complications including cauda equina syndrome.

CMS-HCC V28

HCC 92

RAF 0.479

CMS-HCC V24

HCC 39

RAF 0.401

ACA/HHS

HCC 55

Varies by metal level

ESRD/PACE

HCC 39

RAF 0.092

RXHCC

N/A

—

Not mapped

Code Book Path

Official
M46Other inflammatory spondylopathies
M46.2Osteomyelitis of vertebra
M46.26Osteomyelitis of vertebra, lumbar region

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M46.26 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M46.26 in this effective period.

Related Child Codes

Official
M46.20Osteomyelitis of vertebra, site unspecified
M46.21Osteomyelitis of vertebra, occipito-atlanto-axial region
M46.22Osteomyelitis of vertebra, cervical region
M46.23Osteomyelitis of vertebra, cervicothoracic region
M46.24Osteomyelitis of vertebra, thoracic region

Includes

Official

ICD-10-CM does not list Includes notes for M46.26 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M46.26 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M46.26 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M46.26 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M46.26 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Documentation of bone infection specifically in lumbar vertebrae
Clinical presentation including lower back pain and systemic infection signs
Imaging confirmation of lumbar vertebral osteomyelitis
Neurological examination for cauda equina or nerve root involvement

MEAT Support

HCC Buddy guidance
Documentation of bone infection specifically in lumbar vertebrae
Clinical presentation including lower back pain and systemic infection signs
Imaging confirmation of lumbar vertebral osteomyelitis
Neurological examination for cauda equina or nerve root involvement

Audit Caution

HCC Buddy guidance
Using junction codes when pure lumbar involvement is present
Confusing with disc space infection at lumbar level
Missing specific lumbar vertebral documentation
Not distinguishing from mechanical back pain

Common Mistakes

HCC Buddy guidance
M4625 — Thoracolumbar osteomyelitis involves junction with thoracic spine
M4627 — Lumbosacral osteomyelitis involves junction with sacral spine
M46.36 — Lumbar disc infection affects disc space, not vertebral body
M48.06 — Lumbar spinal stenosis is degenerative condition

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is M46.26 an HCC code?

Yes. M46.26 (Osteomyelitis of vertebra, lumbar region) maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24), with a community non-dual aged RAF of 0.479. It is billable for payment year 2026.

Coder answer: M46.26 is billable and maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
M46.26
Description
Osteomyelitis of vertebra, lumbar region
HCC (V28)
HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
RAF
0.479
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
0.479
V24HCC 39, Bone/Joint/Muscle Infections/Necrosis
0.401
ESRDHCC 39, Bone/Joint/Muscle Infections/Necrosis
0.092

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work M46.26 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M46.26

For M46.26 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M46.26 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M46.26 is the ICD-10-CM diagnosis code for osteomyelitis of vertebra, lumbar region. A bone infection affecting the vertebrae in the lower back or lumbar region of the spine. M46.26 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering spondylopathies (m45-m49).

Under the CMS-HCC V28 risk adjustment model, M46.26 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, M46.26 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Use M46.26 when the provider wording supports osteomyelitis of vertebra, lumbar region. Check the FY2026 tabular notes and the full code path before the final code choice. Because M46.26 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M46.26 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use M46.26 when the provider wording supports osteomyelitis of vertebra, lumbar region. Check the FY2026 tabular notes and the full code path before the final code choice.
  • •For this DOS, capture the provider's current assessment and the care action documented for osteomyelitis of vertebra, lumbar region. Keep the checklist tied to the note.
  • •Do not swap M46.26 with M46.20. The FY2026 tabular describes M46.20 as osteomyelitis of vertebra, site unspecified. Follow the documented detail.
  • •M46.26 maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. The mapping does not replace the documentation review. The code still has to match the note.
  • •Ask Buddy to show the official notes for M46.26 or compare its code path with M46.20.

Clinical Significance

Lumbar vertebral osteomyelitis is a serious infection that can cause significant functional disability and neurological complications including cauda equina syndrome. The lumbar location affects weight-bearing capacity and requires aggressive treatment to prevent permanent disability.

Documentation Requirements

  • ✓Documentation of bone infection specifically in lumbar vertebrae
  • ✓Clinical presentation including lower back pain and systemic infection signs
  • ✓Imaging confirmation of lumbar vertebral osteomyelitis
  • ✓Neurological examination for cauda equina or nerve root involvement
  • ✓Laboratory evidence of infection including cultures when possible
  • ✓Assessment of weight-bearing capacity and functional status
  • ✓Documentation of antimicrobial therapy and treatment response
  • ✓Monitoring for complications including abscess or neurological deterioration

Commonly Confused Codes

  • •M4625: Thoracolumbar osteomyelitis involves junction with thoracic spine
  • •M4627: Lumbosacral osteomyelitis involves junction with sacral spine
  • •M46.36: Lumbar disc infection affects disc space, not vertebral body
  • •M48.06: Lumbar spinal stenosis is degenerative condition
  • •M54.5: Low back pain is symptom, not bone infection diagnosis

Child Codes

M46.20Osteomyelitis of vertebra, site unspecified
HCC 92
M46.21Osteomyelitis of vertebra, occipito-atlanto-axial region
HCC 92
M46.22Osteomyelitis of vertebra, cervical region
HCC 92
M46.23Osteomyelitis of vertebra, cervicothoracic region
HCC 92
M46.24Osteomyelitis of vertebra, thoracic region
HCC 92
M46.25Osteomyelitis of vertebra, thoracolumbar region
HCC 92
M46.26Osteomyelitis of vertebra, lumbar region
HCC 92
M46.27Osteomyelitis of vertebra, lumbosacral region
HCC 92
M46.28Osteomyelitis of vertebra, sacral and sacrococcygeal region
HCC 92

Code Hierarchy

└M46Other inflammatory spondylopathies└M46.2Osteomyelitis of vertebra└M46.26Osteomyelitis of vertebra, lumbar region
└M46.26Osteomyelitis of vertebra, lumbar region

Because M46.26 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

M46.26 maps to CMS-HCC V28 category 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. Because M46.26 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

Work M46.26 in HCC Buddy

Open M46.26 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

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