Glossary · Clinical

Posterolateral fusion (PLF)

Posterolateral fusion (PLF) is a spinal arthrodesis technique in which bone graft is placed along the transverse processes and posterolateral gutters to achieve bony union between vertebral segments, without entering the disc space. It is the foundational posterior fusion construct and the benchmark against which interbody techniques are compared.

Verified May 8, 2026 · 7 sources ↓

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Definition

Source · Editorial summary grounded in 7 cited references ↓

Posterolateral fusion involves decortication of the transverse processes, facet joints, and lateral elements of the spine, followed by placement of autograft, allograft, or a combination of bone graft materials in the posterolateral gutters on one or both sides. The technique relies on creeping substitution across these bony surfaces to achieve solid arthrodesis. It is most commonly performed at the lumbar or lumbosacral levels and is frequently paired with posterior segmental instrumentation—pedicle screws and rods—to provide immediate stability while the biologic fusion matures.

PLF differs fundamentally from interbody techniques (PLIF, TLIF, ALIF) because it does not prepare or occupy the intervertebral disc space. This distinction drives separate CPT code selection: PLF maps to the 22600–22614 range (posterior or posterolateral arthrodesis), whereas posterior interbody work maps to 22630–22634. When a surgeon performs both a posterolateral arthrodesis and a posterior interbody fusion at the same level during the same session, the combined-technique code 22633 is correct—not two separate codes stacked together.

From a clinical standpoint, PLF is indicated for degenerative disc disease, spondylolisthesis, spinal stenosis requiring decompression plus stabilization, and adjacent-segment disease. Fusion rates vary with the number of levels, patient comorbidities (smoking, diabetes, osteoporosis), and whether rigid internal fixation is used. Understanding the procedural anatomy—specifically that PLF targets structures posterior to the posterior longitudinal ligament—is essential for both operative documentation and downstream coding accuracy.

Why it matters

Misidentifying PLF as an interbody procedure—or failing to distinguish a stand-alone PLF from a combined PLF-plus-interbody construct—directly affects which CPT code is reported. Billing 22630 (posterior interbody) when the operative report documents only posterolateral graft placement without disc space preparation constitutes miscoding and creates audit risk under CMS LCD L37848 for lumbar spinal fusion. Conversely, under-coding a combined PLF/TLIF encounter by reporting only 22612 instead of 22633 leaves legitimate reimbursement on the table. Payer denials and post-payment audits in spinal fusion are among the highest-volume targets in orthopedic compliance programs; operative report specificity about graft location and disc space entry is the primary defense.

Common mistakes

Where people most often go wrong with this concept.

Source · Editorial brief grounded in cited references ↓

Reporting 22630 (posterior interbody) for a pure PLF that never entered the disc space—these are distinct techniques with distinct CPT codes.
Stacking 22612 + 22630 at the same level instead of using the single combined-technique code 22633 when both posterolateral and posterior interbody work were performed.
Omitting the add-on code +22614 for each additional interspace when PLF spans multiple levels.
Failing to separately report posterior segmental instrumentation add-on codes (e.g., +22842) because the coder assumed instrumentation was bundled into the arthrodesis code—it is not; it requires a separate add-on code.
Documenting 'posterior fusion' in the operative report without specifying whether graft was placed in the posterolateral gutters, in the disc space, or both—vague documentation is the root cause of most PLF coding errors.
Applying Modifier 51 to instrumentation add-on codes, which are exempt from multiple-procedure reduction rules.

Related codes

Codes commonly involved when this concept appears in practice.

CPT

ICD-10

M43.16 M43.17 M51.16 M51.17

Modifiers

62 Two surgeons 80 Assistant surgeon 51 Multiple procedures 58 Staged or related procedure 78 Unplanned return to OR AS PA / NP / CNS assistant at surgery

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01What is the correct CPT code for a single-level lumbar PLF without interbody work?

CPT 22612 covers arthrodesis using a posterior or posterolateral technique at a single lumbar interspace. Add +22614 for each additional interspace treated at the same session.

02Can I bill both 22612 and 22630 at the same lumbar level when the surgeon does both a PLF and a TLIF?

No. When both posterolateral and posterior interbody techniques are performed at the same level, the correct code is the combined-technique code 22633. Billing 22612 and 22630 separately at the same level constitutes unbundling and is a common audit target.

03Is posterior segmental instrumentation included in the PLF code?

No. Pedicle screw and rod instrumentation requires a separate add-on code (e.g., +22842 for 3–6 vertebral segments). These add-on codes are not subject to Modifier 51 multiple-procedure reduction.

04How does PLF differ from PLIF anatomically?

PLF places bone graft along the posterior and lateral bony elements—transverse processes and facet joints—entirely outside the disc space. PLIF removes disc material and places interbody graft or a cage directly inside the intervertebral disc space through a posterior midline approach. The two techniques target different anatomical compartments, which is why they carry different CPT codes.

05Does CMS require a specific diagnosis code to cover lumbar PLF under Medicare?

Yes. CMS LCD L37848 (Lumbar Spinal Fusion) specifies covered indications. Diagnosis codes must document conditions such as spondylolisthesis, severe degenerative disc disease, or spinal instability after conservative treatment failure. Claims without a covered ICD-10-CM diagnosis are subject to denial regardless of whether the procedure was medically appropriate.

06When two surgeons co-operate on a PLF, which modifier applies?

Modifier 62 (two surgeons) applies when two surgeons of different specialties each perform a distinct part of the procedure and each submits a separate claim. Both surgeons append Modifier 62 to the same primary CPT code. This is distinct from Modifier 80, which designates an assistant surgeon.

Sources & references

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

Mira AI Scribe

When Mira detects operative documentation of a lumbar or lumbosacral posterior fusion, it checks the report for three determinants before suggesting a code: (1) Was the disc space entered and prepared? (2) Was bone graft placed in the posterolateral gutters, the interbody space, or both? (3) How many interspaces were treated? If the report documents decortication of transverse processes and graft placement in the posterolateral gutters only—with no disc space preparation—Mira flags CPT 22612 (lumbar PLF, single interspace) plus +22614 for each additional level. If the report documents both posterolateral graft placement and posterior interbody work at the same level, Mira flags 22633 (combined technique, single interspace) and suppresses 22612 + 22630 to prevent the unbundling error. For pedicle screw instrumentation noted in the report, Mira appends the appropriate posterior segmental instrumentation add-on (e.g., +22842 for 3–6 vertebral segments) and marks it as modifier-51 exempt. Mira also prompts the coder to verify: (a) that the operative report explicitly names the graft harvest site if autograft was used (supporting a separate bone graft harvest code where applicable), and (b) that the diagnosis codes map to a covered indication under CMS LCD L37848. If documentation is ambiguous about disc space entry, Mira raises a clarification flag rather than defaulting to the higher-paying interbody code.

See Mira's approach

TLIF (transforaminal lumbar interbody fusion) is a posterior spinal surgery in which the surgeon accesses the disc space through the foramen to remove disc material and pack a cage with bone graft between two lumbar vertebrae, achieving both decompression and fusion from a single posterior approach. It is reported primarily with CPT 22630 for a single interspace, with add-on codes for each additional level.

PLIF (posterior lumbar interbody fusion) Clinical

PLIF (posterior lumbar interbody fusion) is a spinal fusion technique in which the surgeon accesses the lumbar disc space from the back of the spine, removes the damaged disc, and inserts an interbody spacer or cage to fuse two adjacent vertebrae into a single solid segment.

ALIF (anterior lumbar interbody fusion) Clinical

ALIF (anterior lumbar interbody fusion) is a spinal fusion procedure that accesses the lumbar disc space through an incision in the abdomen, removes the damaged disc, and packs the interspace with bone graft or an interbody device to promote vertebral fusion. It is coded primarily with CPT 22558 and ICD-10-PCS 0SG00A0 for single-level lumbar fusion via open anterior approach.

Spondylolisthesis Clinical

Spondylolisthesis is a spinal condition in which one vertebra slips forward (anterolisthesis) or, less commonly, backward (retrolisthesis) relative to the vertebra below it. It most often occurs at L4–L5 or L5–S1 and ranges in severity from mild instability to frank neurologic compromise.

Autograft Clinical

An autograft is tissue—most commonly bone, tendon, or cartilage—harvested from the same patient who will receive it, eliminating rejection risk and providing the biologic stimulus for successful incorporation.