M40.35 Flatback syndrome, thoracolumbar region

Billable ICD-10-CM code, FY2026.

Applies from M40 Kyphosis and lordosis

Excludes1 (never code together)

• congenital kyphosis and lordosis (Q76.4)
• kyphoscoliosis (M41.-)
• postprocedural kyphosis and lordosis (M96.-)

Code first

• underlying disease

MS-DRG index

Defines the logic of DRG(s) 456-458 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 737.19 Other kyphosis (acquired) (approximate)

Code annotations containing back-references to M40.35

Back-references to M40

• Type 2 Excludes: M43.8 Other specified deforming dorsopathies ("kyphosis and lordosis (M40.-)")
• Type 2 Excludes: M95 Other acquired deformities of musculoskeletal system and connective tissue ("deforming dorsopathies (M40-M43)")

Diagnosis Index entries for M40.35

• Flatback syndrome › thoracolumbar region

Nearby codes

• M40.294 Other kyphosis, thoracic region
• M40.295 Other kyphosis, thoracolumbar region
• M40.299 Other kyphosis, site unspecified
• M40.3 Flatback syndrome
• M40.30 Flatback syndrome, site unspecified
• M40.35 Flatback syndrome, thoracolumbar region (this code)
• M40.36 Flatback syndrome, lumbar region
• M40.37 Flatback syndrome, lumbosacral region
• M40.4 Postural lordosis
• M40.40 Postural lordosis, site unspecified
• M40.45 Postural lordosis, thoracolumbar region