ICD-10-CM · Spine

M51.A3

M51.A3 identifies an annulus fibrosus defect at the lumbosacral intervertebral disc level where the defect size has not been specified in the clinical documentation.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 8
Region: Spine

Drawn from CDCAAPCMedcentralIcdcodesNIH

Documentation tips

What should appear in the chart to support M51.A3.

Source · Editorial brief grounded in 5 cited references ↓

Record defect dimensions explicitly in the operative or imaging report — width and height in millimeters — so you can use M51.A4 (small) or M51.A5 (large) instead of defaulting to M51.A3.
Note the surgical context: was this defect identified at time of discectomy, on post-op MRI, or on a new imaging study? Payers may require procedure history to support the diagnosis.
When lumbosacral disc herniation (M51.17 or M51.27) is also present, document it separately and list it first per the 'code first' instruction in the Tabular List.
Document whether the annular defect is a new finding or a known post-discectomy finding, as this affects clinical decision-making documentation and supports medical necessity for follow-up imaging or closure procedures.
Include the imaging modality and date (MRI preferred) that confirmed the annular defect; vague 'back pain' notes without imaging support will not substantiate M51.A3 on audit.

Related CPT procedures

Procedure codes commonly billed with M51.A3. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

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.

63047 $1,065.49

Lumbar laminectomy at a single vertebral segment that also includes facetectomy and foraminotomy for decompression of the spinal cord, cauda equina, and/or nerve roots — unilateral or bilateral.

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.

72100 $40.42

Radiologic examination of the lumbosacral spine capturing two or three views, used to evaluate the lumbar vertebrae and sacrum for injury, degeneration, or structural abnormality.

99213 $95.19

Established patient office or outpatient visit requiring 20–29 minutes of total time or low-complexity medical decision-making.

99214 $135.61

Office visit for an established patient requiring moderate-complexity medical decision making (MDM), or 30–39 minutes of total provider time on the date of service.

Common coding pitfalls

The recurring mistakes coders make with M51.A3 and adjacent codes.

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

Using M51.A3 when defect size IS documented on imaging — if the MRI report gives dimensions, you must assign M51.A4 (small) or M51.A5 (large); M51.A3 is only correct when size is genuinely absent.
Sequencing M51.A3 as the primary code when active lumbosacral disc herniation is also present — the Tabular 'code first' instruction requires M51.17 or M51.27 to lead.
Confusing the lumbosacral region (M51.A3–M51.A5) with the lumbar region (M51.A0–M51.A2) — the lumbosacral level is L5–S1; lumbar codes apply to L1–L5 levels above it.
Assigning M51.A3 for a cervical or thoracic annular defect — M51.A codes are restricted to lumbar and lumbosacral regions; cervical disc disorders fall under M50 and have no parallel annular defect subcodes.
Omitting M51.A3 entirely from post-discectomy encounters where the surgeon documents and addresses an annular defect — failing to code it leaves clinical complexity uncaptured and may underrepresent the visit's medical necessity.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M51.A3 is used when imaging or surgical findings confirm a defect in the outer fibrous ring (annulus fibrosus) of a lumbosacral disc and the documentation does not characterize the defect as small (<6 mm wide and <4 mm high) or large (≥6 mm wide and ≥4 mm high). The code is most commonly applied in post-discectomy follow-up encounters, where annular defects are assessed as a known complication or residual finding. If the defect size is documented, you must use M51.A4 (small, lumbosacral) or M51.A5 (large, lumbosacral) instead — M51.A3 is explicitly the fallback when size is absent from the record.

The ICD-10-CM Tabular List instructs you to code first the associated lumbosacral disc herniation if applicable: M51.17 (disc degeneration, lumbosacral) or M51.27 (disc displacement with radiculopathy, lumbosacral). This sequencing rule means M51.A3 functions as an additional/secondary code in most herniation encounters — list the herniation first, then M51.A3 to capture the annular defect. Do not use M51.A3 as a standalone primary code when active lumbosacral disc herniation is also documented.

This code family (M51.A–M51.A5) was introduced to give spine surgeons a precise way to document annular defects occurring after discectomy. Payers and researchers are increasingly tracking defect size because large annular defects carry higher re-herniation risk, and emerging closure devices target that population. Defaulting to M51.A3 (unspecified size) when size is actually documented on the MRI report will cost the practice coding specificity and may invite payer scrutiny on related device or procedure claims.

Sibling codes

Other billable codes under M51.A (laterality / anatomic variants).

M51.A4

Intvrt annulus fibrosus defect, small, lumbosacral region

M51.A1

Intervertebral annulus fibrosus defect, small, lumbar region

M51.A0

Intvrt annulus fibrosus defect, lumbar region, unsp size

M51.A5

Intvrt annulus fibrosus defect, large, lumbosacral region

M51.A2

Intervertebral annulus fibrosus defect, large, lumbar region

Frequently asked questions

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

01What is the difference between M51.A3, M51.A4, and M51.A5?

All three describe lumbosacral annulus fibrosus defects. M51.A3 is unspecified size; M51.A4 is small (defect <6 mm wide and <4 mm high); M51.A5 is large (≥6 mm wide and ≥4 mm high). Use M51.A3 only when the clinical record truly lacks size information.

02Do I always need to list a disc herniation code alongside M51.A3?

Only when herniation is also documented. The Tabular List says 'code first, if applicable' M51.17 or M51.27 — it is conditional. If no herniation is present or documented, M51.A3 can stand alone as the relevant diagnosis.

03Can M51.A3 be used for a defect found during initial discectomy, not just post-op follow-up?

Yes. The code describes the anatomical finding, not the timing. If an annular defect at the lumbosacral level is identified and documented intraoperatively and size is not specified, M51.A3 is appropriate for that encounter.

04Is M51.A3 valid for a cervicothoracic or lumbar (non-lumbosacral) defect?

No. M51.A3 is specific to the lumbosacral region (L5–S1). Lumbar region defects (L1–L5) use M51.A0 (unspecified size), M51.A1 (small), or M51.A2 (large). There are no parallel M51.A codes for cervical or thoracic levels.

05When was this code added to ICD-10-CM?

The M51.A code family was introduced to give spine surgeons a structured way to document annular defects — particularly post-discectomy — distinguishing small from large defects, which carry different re-herniation risk profiles. The codes were effective as part of a recent ICD-10-CM update cycle.

06Does M51.A3 apply to an annular tear that is not post-surgical?

The code classifies any documented annular fibrosus defect at the lumbosacral level regardless of etiology — traumatic, degenerative, or post-discectomy. However, the clinical impetus for the code family was post-discectomy documentation, so ensure the defect is confirmed by imaging or direct visualization regardless of cause.

07What imaging supports M51.A3?

MRI is the standard modality to visualize annular defects; a CT myelogram is an acceptable alternative. The report should describe the defect location at the lumbosacral level. If the report gives dimensions, use M51.A4 or M51.A5 instead of M51.A3.

Sources & references

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

Mira AI Scribe

Mira AI Scribe captures the imaging report findings that anchor M51.A3: defect location (lumbosacral/L5–S1), defect dimensions if stated, the presence of prior discectomy, and any associated herniation diagnosis. Capturing this in the encounter note prevents a drop to unspecified M51.A3 when size is documented, and ensures correct 'code first' sequencing of M51.17 or M51.27 — avoiding a sequencing error that triggers payer edits.

See how Mira captures M51.A3 documentation