XLIF / LLIF (lateral lumbar interbody fusion)

XLIF and LLIF describe a family of lateral-access lumbar interbody fusion procedures performed with the patient in the lateral decubitus position. The surgeon spreads or mobilizes the abdominal musculature to reach the retroperitoneal space, then traverses or retracts the iliopsoas muscle to expose the anterolateral disc. The disc is excised, the endplates are prepared, and an interbody device—typically a wide-footprint PEEK or titanium cage packed with bone graft—is impacted into the disc space. Because no posterior midline incision is made and the spinal canal is not directly entered, significant decompression may require a separate posterior stage. The procedure is most commonly performed at L2–L3 through L4–L5; the L5–S1 level is generally inaccessible due to the iliac crest.

From a coding standpoint, the North American Spine Society (NASS) and device-manufacturer guidance align on using CPT 22558 (anterior lumbar interbody arthrodesis, single interspace) to capture the primary fusion, because the operative target—the anterior disc space and vertebral body—matches the anatomical description of an anterior approach regardless of the lateral skin entry. An interbody biomechanical device is separately reportable with add-on code +22853. If a supplemental posterior construct is placed through a separate posterior incision at the same session, the posterior fusion (e.g., 22612) and posterior instrumentation (e.g., +22840) are reported in addition, with each code justified by its own distinct approach and operative work.

Since early 2026, Medicare has removed numerous spine procedures—including many lumbar fusion codes—from the Inpatient Only (IPO) list and simultaneously added them to the Ambulatory Surgery Center Covered Procedures List (CPL), expanding the settings in which XLIF/LLIF cases may be reimbursed. Site-of-service verification is therefore a mandatory pre-submission step.

Using the wrong primary fusion code—most commonly 22630 (posterior interbody technique) instead of 22558 (anterior interbody technique)—will trigger payer audits or outright denials because the claim's procedure descriptor will not match operative notes describing a lateral, retroperitoneal corridor. NCCI edits also bundle duplicate base codes when multiple approaches are reported at the same interspace without appropriate modifier justification, meaning an unbundled or mis-coded XLIF claim can result in recoupment of the entire surgical episode. Additionally, because 2026 Medicare site-of-service policy now permits many lumbar fusion codes in hospital outpatient and ASC settings, billing XLIF under an inpatient-only assumption without confirming current payer policy leaves legitimate reimbursement on the table.