ICD-10-CM · Spine

M46.27

M46.27 captures bone infection (osteomyelitis) localized to the vertebrae of the lumbosacral region — specifically the junction of the lumbar spine and sacrum (L5-S1 level and associated structures).

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 15
Region: Spine

Drawn from CDCICD10DataAAPCCMSUnboundmedicine

Documentation tips

What should appear in the chart to support M46.27.

Source · Editorial brief grounded in 5 cited references ↓

Identify the spinal region by name — 'lumbosacral' or 'L5-S1 junction' — not just 'lower back'; unspecified site defaults to M46.20.
Record the organism if identified (e.g., Staphylococcus aureus from blood culture or biopsy); add a causative organism code (B95–B96) as an additional diagnosis when the pathogen is documented.
Document the basis for diagnosis: MRI findings (signal change at L5-S1 vertebral endplates, paraspinal/epidural phlegmon), bone biopsy results, or positive blood cultures with clinical correlation.
Note any concurrent intervertebral disc involvement — if discitis at the lumbosacral level is also present, M46.37 should be coded in addition to M46.27.
Capture comorbidities that predispose to vertebral osteomyelitis (diabetes mellitus, immunosuppression, IV drug use, recent spinal procedure) — these influence DRG severity and support medical necessity.
Specify whether the infection is acute, subacute, or chronic if the attending documents it; this supports clinical justification even though M46.27 itself does not have subtype codes.

Related CPT procedures

Procedure codes commonly billed with M46.27. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

22533 $1,547.80

Spinal fusion of a lumbar vertebral segment performed through a lateral extracavitary approach, including minimal discectomy to prepare the interspace (not performed solely for decompression).

22558 $1,423.88

Anterior interbody arthrodesis of the lumbar spine using an anterior or anterolateral approach, including the minimal discectomy required to prepare the interspace for fusion.

22612 $1,467.64

Posterior or posterolateral lumbar arthrodesis of a single interspace, performed via a posterior approach with bone graft and typically pedicle screw fixation to achieve vertebral segment fusion.

22630 $1,510.72

Posterior interbody arthrodesis of a single lumbar interspace, including laminectomy and/or discectomy performed to prepare the interspace for fusion rather than for decompression.

22800 $1,312.99

Posterior spinal arthrodesis for deformity correction spanning up to 6 vertebral segments, with or without application of a body cast.

22840 $668.35

Posterior non-segmental instrumentation placed during spinal surgery, using rods, hooks, or wires that span multiple vertebral levels without anchoring at each intervening segment.

22842 $680.04

Posterior segmental spinal instrumentation spanning 3 to 6 vertebral segments, reported as an add-on to the primary spinal procedure code.

27280 $1,283.60

Open arthrodesis of the sacroiliac joint, including bone graft harvest and instrumentation when used

72148 $191.72

Non-contrast MRI of the lumbar spine used to evaluate disc pathology, spinal stenosis, nerve root compression, and other structural abnormalities without administration of contrast material.

72158 $318.31

MRI of the lumbar spinal canal and its contents performed first without contrast, then repeated after contrast administration for enhanced visualization.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

20615 $249.50

Aspiration and injection procedure to treat a bone cyst — fluid is drawn out and a therapeutic agent is injected to promote healing.

22325 $1,444.25

Open posterior reduction and stabilization of a lumbar vertebral fracture or dislocation, performed through a posterior surgical approach.

22326 $1,473.65

Open treatment of a cervical spine fracture and/or dislocation, performed at a single vertebral level in the neck.

22327 $1,503.37

Open posterior treatment and/or reduction of a single fractured or dislocated thoracic vertebral segment, performed through a posterior approach.

Common coding pitfalls

The recurring mistakes coders make with M46.27 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Using M46.26 (lumbar region) when the documentation specifically says 'lumbosacral' — the lumbosacral region has its own code (M46.27) and the two are not interchangeable.
Coding M46.27 alone when discitis is also documented at the same level — M46.37 (Infection of intervertebral disc, lumbosacral region) must be added separately; osteomyelitis and discitis are distinct codes even when co-located.
Defaulting to M86.9 (Osteomyelitis, unspecified) instead of M46.27 when the vertebral location is clearly documented — M86.9 is a non-specific fallback and will not route to the correct DRG.
Omitting the causative organism code — when the pathogen is identified via culture or biopsy, pairing M46.27 with a B95–B96 code is standard practice and supports complete documentation.
Confusing M46.27 with M46.28 (sacral and sacrococcygeal region) — lumbosacral refers to the L5-S1 transition zone, not the sacrum itself; review imaging reports carefully before selecting between these adjacent codes.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Use M46.27 when the physician documents osteomyelitis of a vertebral body confirmed or localized to the lumbosacral region. This is distinct from lumbar region osteomyelitis (M46.26) and sacral/sacrococcygeal osteomyelitis (M46.28) — the lumbosacral designation applies specifically when the infection involves the L5-S1 junction zone. Common clinical scenarios include hematogenous vertebral osteomyelitis, post-procedural spinal infection, or contiguous spread from an adjacent infected disc or soft tissue structure.

M46.27 is a spondylopathy code under Chapter 13 (M00–M99) and sits within the M46.2 parent category (Osteomyelitis of vertebra). It does not include infection of the intervertebral disc itself — pyogenic discitis at the lumbosacral level maps to M46.37. If both vertebral osteomyelitis and discitis are documented at the same region, code both. Do not default to M46.20 (site unspecified) when the operative report, MRI, or attending note identifies the lumbosacral level.

For DRG assignment, M46.27 routes to MS-DRG 539/540/541 (Osteomyelitis with/without MCC/CC) in most inpatient stays, and may also drive MS-DRG 456–458 when spinal fusion is performed concurrently. Outpatient orthopedic practices most often encounter this code in the context of post-operative wound infections or when managing patients referred for evaluation of back pain with fever and elevated inflammatory markers.

Sibling codes

Other billable codes under M46.2 (laterality / anatomic variants).

M46.23

Osteomyelitis of vertebra, cervicothoracic region

M46.25

Osteomyelitis of vertebra, thoracolumbar region

M46.21

Osteomyelitis of vertebra, occipito-atlanto-axial region

M46.28

Osteomyelitis of vertebra, sacral and sacrococcygeal region

M46.26

Osteomyelitis of vertebra, lumbar region

M46.20

Osteomyelitis of vertebra, site unspecified

M46.24

Osteomyelitis of vertebra, thoracic region

M46.22

Osteomyelitis of vertebra, cervical region

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01What is the difference between M46.26 and M46.27?

M46.26 covers osteomyelitis limited to the lumbar vertebrae (L1–L4 zone), while M46.27 applies when the infection is at the lumbosacral junction (L5-S1). Use the code that matches the documented anatomical site — do not substitute one for the other based on proximity.

02Should I also code the organism when using M46.27?

Yes. When the causative pathogen is identified through culture, biopsy, or serology, add a secondary code from B95 (Streptococcus/Staphylococcus) or B96 (other bacterial agents) to fully describe the infection. Payers and DRG groupers use the organism code to assess complexity.

03Is M46.37 required alongside M46.27 if discitis is also present at the lumbosacral level?

Yes. Osteomyelitis of the vertebra and infection of the intervertebral disc are separately classified even when they occur at the same spinal level. Document both diagnoses explicitly and code both M46.27 and M46.37 when the physician identifies concurrent vertebral and disc infection at the lumbosacral region.

04Which MS-DRGs does M46.27 trigger on an inpatient claim?

M46.27 maps to MS-DRG 539 (Osteomyelitis with MCC), 540 (with CC), and 541 (without CC/MCC) as the principal diagnosis. If spinal fusion is performed during the same admission, it may shift assignment to MS-DRG 456–458 depending on the presence of MCC/CC.

05Can M46.27 be used for a post-operative spinal infection?

M46.27 classifies vertebral osteomyelitis by anatomical site regardless of etiology — hematogenous, post-procedural, or contiguous spread. If the infection is explicitly documented as a complication of a prior spinal procedure, also consider whether a complication code (e.g., T84.69XA or similar postprocedural infection code) should be sequenced with it, depending on the clinical context and payer requirements.

06Does M46.27 require a 7th-character extension?

No. M46.27 is an M-code under Chapter 13 (musculoskeletal diseases) and does not use 7th-character extensions. The A/D/S extension system applies only to injury codes (S- and T-codes). M46.27 is complete as a 5-character billable code.

07What imaging finding best supports M46.27 in the medical record?

MRI is the gold standard — document T1 hypointensity and T2/STIR hyperintensity of the L5 or S1 vertebral body with endplate irregularity. CT findings of bony destruction at the lumbosacral level and bone biopsy confirming osteomyelitis also definitively support the diagnosis. Plain X-ray changes (disc space narrowing, endplate erosion) appear late and are less specific but still documentable.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

The Mira AI Scribe captures the treating physician's documented spinal region (lumbosacral/L5-S1), MRI or CT imaging findings (vertebral endplate erosion, marrow edema, paraspinal abscess), organism if cultured, and any concurrent disc space involvement — all at the point of encounter. This prevents the coder from falling back to M46.20 (site unspecified) or M86.9 (osteomyelitis unspecified), either of which undermines DRG severity and invites payer scrutiny on medical necessity.

See how Mira captures M46.27 documentation