ICD-10-CM · Spine

M46.55

Infective spondylopathy of non-pyogenic or atypical origin affecting the junction of the thoracic and lumbar spine (T12-L1 region), where the infectious process does not fall under more specific categories such as tuberculosis or brucellosis.

Verified May 8, 2026 · 2 sources ↓

Status: Billable
Chapter: 13
Related CPT: 10
Region: Spine

Drawn from CDCICD

Documentation tips

What should appear in the chart to support M46.55.

Source · Editorial brief grounded in 2 cited references ↓

Explicitly name the thoracolumbar junction (T12-L1) in the clinical note — 'thoracolumbar region' is required to support M46.55 over M46.54 (thoracic) or M46.56 (lumbar).
Document the infective etiology: confirmed pathogen, presumed organism based on culture or serology, or clinical diagnosis of infective spondylopathy with supporting lab/imaging findings.
Record MRI findings that confirm spinal infection at the thoracolumbar level — endplate signal change, disc space involvement, paraspinal or epidural abscess, or vertebral osteomyelitis.
Add a causative organism code (e.g., B95.x for streptococcus/staphylococcus, B96.x for other bacteria) as a secondary code when the pathogen is identified by culture, PCR, or biopsy.
If a spinal biopsy or aspiration was performed to identify the organism, document the procedure and results to substantiate the infective diagnosis and support medical necessity for surgical intervention.
Note any prior spine procedures, IV drug use, immunocompromised status, or contiguous infection source — these support the clinical plausibility of an infective spondylopathy and reduce audit risk.

Related CPT procedures

Procedure codes commonly billed with M46.55. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

22800 $1,312.99

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

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.

22102 $702.09

Partial excision of a posterior lumbar vertebral component — such as the spinous process, lamina, or facet — to remove an intrinsic bony lesion at a single vertebral segment.

63030 $898.15

Single-interspace lumbar laminotomy with nerve root decompression, including partial facetectomy, foraminotomy, and/or herniated disc excision performed via open surgical technique.

63056 $1,404.84

Lumbar spinal cord and nerve root decompression via transpedicular approach, single segment, including transfacet or lateral extraforaminal variants for far lateral disc herniations.

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.

20225 $364.74

Percutaneous bone biopsy using a trocar or needle targeting deep skeletal structures such as the vertebral body or femur.

22899 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M46.55 and adjacent codes.

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

Assigning M46.55 when the infection is due to tuberculosis — TB of the spine maps to M49.85 (spondylopathy in diseases classified elsewhere, thoracolumbar region), not M46.55.
Using M46.55 for the lumbar region: if imaging and clinical documentation identify L1-L5 as the primary site, M46.56 (lumbar) is correct; M46.55 is specific to the T12-L1 junction.
Omitting the secondary organism code when the pathogen is documented — payers and auditors expect a B95–B97 or specific infectious disease code alongside M46.55 when culture or serology results are available.
Defaulting to M46.50 (site unspecified) when the record actually documents a specific region — unspecified codes attract scrutiny and may delay authorization for advanced imaging or surgery.
Confusing infective spondylopathy with inflammatory (non-infective) spondylopathy — ankylosing spondylitis and similar conditions fall under M45.x, not M46.5x.

Clinical context

Source · Editorial summary grounded in 2 cited references ↓

M46.55 applies when an infectious or inflammatory process of the spine is localized to the thoracolumbar region and the causative organism or condition places it outside the more specific spondylopathy categories (e.g., tuberculosis of the spine is M49.85, not M46.55). The thoracolumbar region in ICD-10-CM refers to the junction zone spanning T12 and L1. Use M46.55 when the documented infection involves vertebrae or disc space at that junction and the provider has documented an infective etiology that qualifies as 'other' — such as fungal spondylitis, brucellar spondylitis not coded elsewhere, or post-procedural spinal infection when a more specific code does not apply.

The parent code M46.5 (Other infective spondylopathies) carries region-specific fifth-character options: M46.50 (site unspecified), M46.51 (occipito-atlanto-axial), M46.52 (cervical), M46.53 (cervicothoracic), M46.54 (thoracic), M46.55 (thoracolumbar), M46.56 (lumbar), M46.57 (lumbosacral), M46.58 (sacral/sacrococcygeal), M46.59 (multiple sites). Select M46.55 only when clinical and imaging documentation specifically identifies the thoracolumbar junction as the affected region. If infection spans multiple regions, consider M46.59.

This code commonly appears in spine-focused orthopedic and neurosurgical practices managing vertebral osteomyelitis or discitis workups at the thoracolumbar junction. It supports medical necessity for advanced imaging (MRI), interventional biopsy, and surgical debridement or fusion procedures. A causative organism code (B95–B97 or specific organism chapter) should be sequenced as an additional code when the pathogen is identified.

Sibling codes

Other billable codes under M46.5 (laterality / anatomic variants).

M46.53

Other infective spondylopathies, cervicothoracic region

M46.51

Oth infective spondylopathies, occipito-atlanto-axial region

M46.59

Other infective spondylopathies, multiple sites in spine

M46.58

Oth infective spondylopathies, sacr/sacrocygl region

M46.50

Other infective spondylopathies, site unspecified

M46.54

Other infective spondylopathies, thoracic region

M46.57

Other infective spondylopathies, lumbosacral region

M46.52

Other infective spondylopathies, cervical region

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 2 cited references ↓

01What distinguishes M46.55 from M46.54 (thoracic) and M46.56 (lumbar)?

M46.55 is region-specific to the thoracolumbar junction (T12-L1). If the primary infectious involvement is in the mid-thoracic vertebrae, use M46.54. If the disease center is L1-L5, use M46.56. When imaging reports specify the T12-L1 junction, M46.55 is correct.

02Should I code the causative organism separately when using M46.55?

Yes. ICD-10-CM instructs coders to use an additional code to identify the infectious agent when known. Sequence B95–B97 (bacteria) or the relevant organism chapter code as a secondary diagnosis alongside M46.55.

03Can M46.55 be used for post-surgical spinal infection at the thoracolumbar junction?

It depends on documentation. Post-procedural spinal infection may be more precisely coded with T84.x (complication of internal orthopedic device) or T81.x (postprocedural infection) depending on the clinical scenario. Consult the attending physician's documentation and the ICD-10-CM guidelines on postprocedural complications before defaulting to M46.55.

04Does M46.55 require a 7th character extension?

No. M46.55 is an M-code (musculoskeletal chapter). Seventh-character extensions for encounter type (A/D/S) apply to S-codes (injury codes), not M-codes.

05How does M46.55 interact with MRI authorization for the thoracolumbar spine?

M46.55 is a recognized indication for thoracic and lumbar MRI. Pair it with documented clinical findings (fever, elevated ESR/CRP, neurologic signs) and note whether contrast is planned — MRI with contrast (CPT 72148/72158) is typically required for spinal infection workup and payer LCDs generally require a documented infective diagnosis code to authorize it.

06If the infection spans both the thoracolumbar and lumbar regions, which code applies?

Use M46.59 (Other infective spondylopathies, multiple sites) when the infectious process is documented across more than one spinal region. M46.55 is appropriate only when the thoracolumbar junction is the sole or primary documented site.

07Is M46.55 billable on its own, or does it always need a secondary code?

M46.55 is a billable standalone code and can be submitted without a secondary organism code when the pathogen is unidentified. However, once culture or serology confirms an organism, adding the appropriate B-code is required per ICD-10-CM guidelines and improves clinical specificity for payer review.

Sources & references

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

01CDC ICD-10-CM Tabular List 2026 (FY2026, effective Oct 1, 2025)
02ICD-10-CM Official Guidelines for Coding and Reporting FY2026

Mira AI Scribe

Mira's AI scribe captures vertebral level specificity (T12-L1 junction), MRI signal characteristics confirming discitis or osteomyelitis, organism identification from blood or tissue culture, and any history of prior spinal procedure or immunosuppression — all of which anchor M46.55 and prevent a downcode to the unspecified M46.50 or a mismatch to an adjacent region code.

See how Mira captures M46.55 documentation