Defect or stress fracture of the posterior vertebral arch (pars interarticularis) located specifically at the sacral and sacrococcygeal spinal levels, classified as an acquired deforming dorsopathy rather than a congenital anomaly.

Documentation tips

What should appear in the chart to support M43.08.

Source · Editorial brief grounded in 3 cited references ↓

• The operative or imaging report must name the sacral or sacrococcygeal level explicitly — 'lower lumbar' is not sufficient to support M43.08.
• Distinguish between spondylolysis (pars defect without slip, M43.08) and spondylolisthesis (slip present, M43.1x); the distinction must be documented by the treating provider, not inferred by the coder.
• Record the imaging modality and findings that confirm the pars defect — CT scan with coronal reconstructions or SPECT bone scan are the most sensitive and should be referenced in the note.
• If conservative care (bracing, PT, activity restriction) has been tried and failed, document duration and response to support medical necessity for any planned procedural intervention.
• Note whether the spondylolysis is unilateral or bilateral at the sacral level, as operative planning and documentation of clinical findings should reflect this detail even though the code does not sub-classify by laterality at this site.

Related CPT procedures

Procedure codes commonly billed with M43.08. 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 M43.08 and adjacent codes.

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

• Assigning M43.08 when imaging identifies an L5 pars defect — L5-level spondylolysis maps to M43.06, not M43.08; the sacrum begins below L5.
• Using M43.08 when the defect has resulted in vertebral slippage — once slip is documented, the correct parent category is M43.1 (spondylolisthesis), which carries its own sacral subcode M43.18.
• Coding M43.08 for a congenital pars anomaly — congenital spondylolysis is excluded from M43.0 and belongs under Q76.2.
• Leaving the diagnosis at the non-billable parent M43.0 instead of extending to M43.08 for the sacral and sacrococcygeal region — payers require the most specific billable code.
• Defaulting to an unspecified lumbar or spine code when the provider note and radiology report both identify the sacral level — that specificity is available and required.

Clinical context

Source · Editorial summary grounded in 3 cited references ↓

Sibling codes

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