Defect or fracture of the pars interarticularis at the lumbar level, without vertebral slippage — coded as acquired spondylolysis confined to the lumbar spine region.

Documentation tips

What should appear in the chart to support M43.06.

Source · Editorial brief grounded in 6 cited references ↓

• Specify the affected lumbar level (e.g., L4 or L5 pars defect) — the code doesn't require a 7th character for level, but level documentation strengthens medical necessity and supports surgical planning codes.
• Record imaging modality and findings explicitly: CT showing pars fracture line, MRI signal change at the pars, or oblique X-ray 'Scotty dog' sign with collar — this directly validates M43.06 over M43.16.
• Document the absence of vertebral slippage. A phrase such as 'no anterolisthesis on standing lateral radiograph' or 'stable pars defect without listhesis' is the clearest protection against a spondylolisthesis upcoding audit.
• Note whether the defect is unilateral or bilateral and whether it is acute (edema on MRI/SPECT) or chronic (sclerotic margins on CT) — this supports conservative vs. surgical management documentation.
• Capture conservative care history (rest, bracing, physical therapy, duration) when coding for injections or surgery, as payers use this to establish medical necessity.

Related CPT procedures

Procedure codes commonly billed with M43.06. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

Common coding pitfalls

The recurring mistakes coders make with M43.06 and adjacent codes.

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

• Coding M43.06 when imaging documents vertebral slippage: any forward displacement meets criteria for M43.16 (spondylolisthesis, lumbar region) — these two codes are mutually exclusive by definition.
• Using M43.06 for congenital spondylolysis: Q76.2 is the correct code for congenital pars defects; the Type 1 Excludes note at M43.0 prohibits M43.06 in that scenario.
• Defaulting to M43.00 (site unspecified) when the operative or radiology report names a specific lumbar level — M43.06 is always preferred over the unspecified parent when lumbar involvement is documented.
• Confusing M43.06 with M43.07 (lumbosacral region): if the pars defect is at L5 with involvement of the lumbosacral junction, review whether M43.07 is more anatomically precise.
• Omitting a secondary pain code when the presenting complaint is low back pain — M54.5x (low back pain) or the appropriate radiculopathy code can be listed as an additional diagnosis to fully reflect the clinical picture.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M43.0 (laterality / anatomic variants).