One of the most frequently asked question about modifiers is “When do I use modifier 51 and when do I use modifier 59?” This article differentiates the use of these modifiers when two or more procedures are performed on the same day.

About modifier 51
Modifier 51 (multiple procedures) is used to inform payers that two or more procedures are being reported on the same day. A claim form (CMS 1500) that has modifier 51 appended to a CPT code(s) tells the payer to apply the multiple procedure payment formula to the CPT code(s) linked to the modifier 51, assuming the payer accepts this modifier.

Some payers may not accept or require the use of this modifier because their computer systems are already programmed to automatically apply the multiple procedure reduction to the lesser-valued code(s). It is important to remember the following conditions that apply to the use of modifier 51:

• No special rules related to the reporting of the code combinations can apply.
• The CPT code(s) cannot be an add-on (CPT Appendix D) or modifier 51 exempt (CPT Appendix E) codes.
• The CPT code(s) must be stand-alone procedures and not inclusive to other procedures performed at the same time.
• Unless your contract with the payer includes a “carve out,” the subsequent procedure(s) is(are) subject to the payer’s multiple procedure payment formula.

The following examples show correct coding and appropriate use of modifier 51; special coding rules (other than documentation of the work and medical necessity) are not required to report the code combination.

Joint injections
Table 1 shows the coding that should be used when a physician performs a joint injection to a major joint (20610) and joint injection to an intermediate joint (20605) during the same session.

By definition, these two codes are stand-alone codes; their descriptions identify them as two separate anatomic locations, and no specific coding rules must be met (other than documentation and medical necessity). Both are subject to the multiple procedure payment reduction.

Arthroscopic shoulder surgery
Table 2 shows the coding that should be used when a physician performs an arthroscopic rotator cuff repair (29827), arthroscopic distal clavicle resection (29824), and arthroscopic subacromial decompression (29826) during the same session.

All three procedures, although performed in the same shoulder, are considered to be in three separate anatomic locations and are differentiated as such by their descriptions. CPT codes 29827 and 29824 are considered stand-alone codes; CPT code 29826 is an add-on code.

Add-on codes may only be reported with an index code (29806–29825, 29827, or 29828) and are not subject to the multiple procedure payment formulas. A modifier 51 is never appended to an add-on code. The only coding rule (other than documentation and medical necessity) that must be met to report this combination is the presence of an arthroscopic parent or index code to allow CPT code 29826 to be reported.

Modifier 51 is appended to CPT code 29824 as the most appropriate modifier because it is a concomitant, stand-alone procedure and is subject to the multiple procedure payment reduction.

Spine surgery
Table 3 shows the appropriate coding for a posterolateral fusion at L3-L4 and L4-L5 (22612, 22614), laminectomy, facetectomy, foraminotomy and decompression at L3-L4 and L4-L5 (63047, 63048), posterior segmental instrumentation at L3-L5, and bone graft harvested from the iliac crest (20937).

CPT codes 22612 and 63047 are both stand-alone codes; when reported together, the lesser-valued procedure is subject to the multiple procedure payment formula. CPT codes 22614, 63048, 22842, and 20937 are add-on codes and are not subject to the multiple procedure payment formula. To report these add-on codes, a parent or index code must be present. CPT code 22612 is a parent code to 22614, 22842, and 20937. CPT code 63047 is a parent code to 63048, 22842, and 20937.

A laminectomy is not considered inclusive to the posterolateral fusion (22612) and special coding rules (other than documentation and medical necessity) do not have to be met to report this code combination. Thus, modifier 51 is the most appropriate modifier to append to the subsequent (lesser-valued) procedure.

To summarize, modifier 51 is appended to a subsequent procedure that is considered a stand-alone code (not an add-on or exempt code) when the following conditions are met:

• Two or more code combinations are reported.
• By definition, the reported codes stand alone.
• Special rules do not have to be met to report the code combination.

Modifier 59
Modifier 59, the distinct procedural service modifier, is reported with a CPT code combination when a coding rule has to be met, when another, more specific modifier (multiple-51 or bilateral-50) will not explain the situation to the payer, or when the code combination is correct, but the payer has a reimbursement edit in place.

According to CPT, modifier 59 is used to support a different session, a different procedure or surgery, a different site or organ system, a separate incision or excision, a separate lesion, or a separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual.

Of critical importance and differentiation is the following statement from CPT: “When another, already established modifier is appropriate, it should be used rather than modifier 59. Only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used.” Thus, if the bilateral or multiple procedure modifiers describe the situation, modifier 59 should not be used—even in cases of a different procedure, a different site, a separate incision, or a separate injury.

The following examples show when modifier 59 should be used because, according to CPT, a coding rule has to be met to report a code combination, modifiers 51 or 50 will not adequately explain the scenario, and the code combinations are reportable together under CPT rules, but Medicare has issued a payment edit (Correct Coding Initiative, or CCI).

To meet a CPT coding rule
To report a chondroplasty during the same surgical session as a meniscal repair on the same knee, the chondroplasty must be performed in a different compartment than the meniscal repair. If the chondroplasty is performed in the same compartment as the repair, the chondroplasty is not separately reportable.

For example, the surgeon documents a chondroplasty performed in the medial and patellofemoral compartments and a meniscal repair in the medial compartment. Modifier 59 is appended to the chondroplasty code to tell the payer that the coding rule to report the chondroplasty (different site) was met (Table 4).

The goal in this case is to obtain reimbursement for the chondroplasty. Reimbursement is expected to be reduced unless a contractual agreement is in place that allows for full reimbursement.

To report the chondroplasty, the coding rule for the separate site must be met. Modifier 59 is linked to the chondroplasty to indicate to the payer that the coding rule has been met. Because modifier 51, the multiple procedure modifier, does not indicate that the coding rule was met, if it were used, a denial as a bundled service would be expected.

Note: This coding combination is based on CPT coding rules. Some payers, such as Medicare, may require reporting a G code (G0289) for the chondroplasty instead of the CPT code (29877).

To best explain the scenario
Consider the following situation: The surgeon documents injections to the right hip joint and the right knee joint on the same day. Both procedures are defined by CPT code 20610.

Modifier 50, indicating a bilateral procedure, cannot be used because the injections are on the same extremity at different joints. Modifier 51, indicating multiple procedures, does not differentiate the injections as being in different locations; if it is used, the second procedure might be denied as a duplicate submission. Modifier 59 is the correct modifier to use because it not only indicates a separate site, it also meets the rule “when a more descriptive modifier will not explain the circumstances, then modifier 59 is used.”

The goal is to be reimbursed for the second injection; a payment reduction should be expected because it is a second procedure performed during the same session, thus triggering the multiple procedure payment reduction.

Addressing a payment edit
In this scenario, a combination of CPT codes describes the procedures, with each code standing alone and describing different anatomic locations, but Medicare has a payment edit in place.

For example, the documentation shows that the surgeon performed a right wrist injection and an injection at the origin/insertion site of the tendon for lateral epicondylitis. Under the American Medical Association’s CPT rules, the surgeon would report codes 20605 for the wrist injection and 20551-51 for the tendon injection. However, under Medicare payment rules, the surgeon must report 20605 and 20551-59.

According to the CPT rules, these two codes represent procedures performed at separate anatomic locations and should be reported using modifier 51. However, Medicare has an edit in place to ensure that, when this code combination is reported, the surgeon must meet distinct procedural rules for Medicare to consider payment. Because Medicare wants to ensure that the surgeon is not reporting 20551 for the injection of the anesthetic agent at the site of, and prior to, the wrist injection, it requires the use of modifier 59 in conjunction with a separate diagnosis for payment to be processed for both procedures. Again, the goal is to be reimbursed for the second injection; a payment reduction should be expected because the multiple procedure payment reductions will typically apply.

Next steps
Orthopaedic practices should review their coding to ensure that modifiers 51 and 59 are being used appropriately to reflect the procedures submitted to payers. Some payers may not accept either modifier, which presents challenges for correct coding. Practices should avoid using modifier 59 with the sole intent of “overriding” a payer edit. Medicare CCI payment edits are not inclusive and do not contain all possible code combinations because Medicare assumes correct coding.

The AAOS offers a coding consultation service (www.aaos.org/coding) and cosponsors coding courses with KarenZupko & Associates (www.karenzupko.com/ortho.html). Orthopaedic surgeons and coders are encouraged to take advantage of these resources when they have coding questions.

Mary LeGrand, RN, MA, CCS-P, CPC, is a senior consultant with KarenZupko & Associates, Inc., who focuses on coding and reimbursement issues in orthopaedic practices. Information in this article has been reviewed by members of the AAOS Coding, Coverage, and Reimbursement Committee.

If you have questions about coding or want to suggest a topic for a future coding article, email aaoscomm@aaos.org