Current Procedural Terminology (CPT) codes serve as the standardized language for reporting medical services and procedures to payers. In spinal surgery, specific codes are utilized to describe the precise nature and extent of the procedures performed. CPT code 22585 is applied exclusively in the context of spinal arthrodesis, commonly known as spinal fusion. Its application is highly specific, designed to account for the work involved when a surgeon addresses multiple levels of the spine during a single operative session. Accurately reporting this code requires a detailed understanding of its definition, its function as an add-on code, and the mandatory primary procedure codes it must accompany for compliant billing.
Defining CPT Code 22585
CPT code 22585 is formally described as “Arthrodesis, anterior interbody technique, including minimal discectomy to prepare interspace (other than for decompression); each additional interspace (List separately in addition to code for primary procedure)”. This indicates the code is used for spinal fusion procedures performed via the anterior approach (from the front of the body). The procedure involves joining two adjacent vertebral bodies across an intervertebral disc space, referred to as an interspace. The code accounts for the surgical work required to fuse an additional interspace beyond the first one, which is covered by a primary CPT code.
The term “interspace” refers to the non-bony compartment between two vertebrae that contains the intervertebral disc. The procedure described by 22585 includes the necessary preparation of this space, such as a minimal discectomy, to receive the bone graft or interbody device. It is a segment-specific code, reported once for every additional interspace fused beyond the initial level. This procedure is distinct from a posterior or posterolateral approach, which involves different surgical trajectories and corresponding CPT codes.
Understanding Add-on Code Mechanics
CPT code 22585 is identified as an “add-on” code, indicated by a plus sign (+) next to the code descriptor. This means the code is never reported as a standalone procedure; it must always be used in conjunction with a designated primary procedure code. Add-on codes represent services performed in addition to the main procedure and typically describe work that is integral to, but distinct from, the primary service.
A significant advantage of an add-on code is its exemption from the Multiple Procedure Reduction Rule. When multiple standard surgical procedures are performed during the same session, payers commonly reduce the reimbursement for the secondary and subsequent procedures. This reduction is based on the premise that some surgical work, like pre-operative and post-operative care, overlaps and should only be paid once. Because add-on codes like 22585 represent additional, discrete surgical work, they are generally reimbursed at 100% of the allowed amount. This exemption simplifies the billing process by removing the need to append Modifier -51, which is typically used to flag secondary procedures subject to payment reduction.
Mandatory Primary CPT Codes
The use of CPT 22585 is contingent upon the correct selection of a base code that describes the primary fusion procedure. Since 22585 describes the fusion of an additional interspace using the anterior interbody technique, the base code must also describe the initial fusion using the same approach. The primary codes are categorized by the anatomical region of the spine—cervical, thoracic, or lumbar—where the initial fusion occurred.
For the cervical region, code 22554 describes the anterior interbody fusion at one level. For the thoracic spine, the base code is 22556. For the lumbar region, the primary code is 22558. In a multi-level procedure, one of these codes is reported for the first interspace fused, and 22585 is reported for each subsequent interspace.
For instance, a three-level anterior lumbar fusion (L3 to S1) involves three interspaces. The primary code 22558 is reported for the first interspace, and CPT 22585 is reported twice for the two additional interspaces. Correctly pairing 22585 with the appropriate anterior primary code is necessary for compliant spinal fusion coding.
Correct Usage and Documentation
Compliant reporting of CPT 22585 hinges on meticulous documentation within the operative report, focusing specifically on the distinct vertebral levels involved in the fusion. The surgeon must clearly identify the specific vertebral bodies and interspaces that are fused during the procedure, such as C5-C6 and C6-C7. This level-specific documentation is the direct justification for reporting one primary code and one unit of 22585 for a two-level fusion, or multiple units of 22585 for more extensive fusions.
A common point of confusion is the method of counting segments, which must be clearly defined in the medical record. For an arthrodesis procedure, the number of interspaces fused determines the units of coding, not the number of vertebrae. Fusing a span across two vertebral bodies, such as L4 and L5, constitutes one interspace, requiring one primary code. If the fusion spans three vertebral bodies, for example L4 to L6, this represents two interspaces (L4-L5 and L5-L6) and requires one primary code plus one instance of 22585.
The detailed operative note must explicitly confirm that the anterior interbody technique, including the minimal discectomy, was performed at each interspace claimed by the use of 22585. Furthermore, payers, including Medicare Administrative Contractors, may have specific local coverage determinations or guidelines that affect the reporting of multiple units of the code. Adherence to these payer-specific rules is necessary to avoid post-payment audits and denials.