Modifiers · CPT modifier

Discontinued out-pt before anesthesia

Modifier 73 tells the payer that an ASC or outpatient hospital facility had to stop a scheduled surgical or diagnostic procedure after the patient was prepped and brought into the procedure room, but before any anesthesia—local, regional block, or general—was given. It is a facility-only modifier and signals that real resources were consumed even though the case never truly started.

Verified May 8, 2026 · 6 sources ↓

Type: CPT
CPT codes use it: 35
Top regions: Foot & ankle, Knee, Hip

Drawn from CMSNovitas SolutionsNoridian MedicareAAPCAMA

When to use modifier 73

Source · Editorial brief grounded in 6 cited references ↓

Use modifier 73 when two conditions are both met: (1) the patient has been surgically prepared and physically moved into the procedure room, and (2) the procedure is halted before any planned anesthesia is administered. The reason for stopping must be a genuine clinical threat to the patient—an unexpected spike in blood pressure, a dangerous cardiac arrhythmia discovered at last-minute monitoring review, or an acute respiratory finding that makes safe anesthesia induction impossible. Elective or convenience-driven cancellations, such as a surgeon deciding the schedule is too full or a patient who simply changes their mind, do not qualify.

Anesthesia for modifier 73 purposes is broadly defined: local blocks, regional nerve blocks, moderate (conscious) sedation, deep sedation, and general anesthesia all count. If none of those were planned at all for the procedure, modifier 73 is the wrong tool—do not append it. When the procedure is stopped after anesthesia has already been delivered, switch to modifier 74 instead.

Modifier 73 belongs exclusively on the facility (ASC or outpatient hospital) claim. The operating surgeon's professional claim uses modifier 53 for discontinued procedures; applying modifier 73 to a CMS-1500 or 837P professional claim is a billing error. Reimbursement under Medicare and most commercial payers is set at 50 percent of the applicable facility fee schedule for the primary intended procedure code. Bill only the primary procedure—do not add secondary planned procedures that were never attempted.

Orthopedic scenarios

Concrete situations in orthopedic practice that warrant modifier 73.

Source · Editorial brief grounded in AAOS coding guidance and cited references ↓

A patient is prepped and wheeled into the OR for a total knee arthroplasty (TKA). Prior to spinal anesthesia induction, the anesthesiologist detects a new, symptomatic left bundle branch block on the pre-induction EKG. The surgical team cancels the case immediately. The ASC bills the TKA CPT code with modifier 73 appended and is reimbursed at 50% of the facility rate.
A patient scheduled for right shoulder arthroscopic rotator cuff repair is positioned, draped, and prepped in the arthroscopy suite. Before the regional interscalene block is administered, pulse oximetry reveals oxygen saturation dropping to 84% on room air. The procedure is aborted. The facility appends modifier 73 to the arthroscopy code on the facility claim.
A patient presenting for closed reduction and internal fixation (ORIF) of a distal radius fracture is brought to the procedure room and prepped. Before IV sedation is started, the nurse notes the patient took full anticoagulation that morning in contradiction to pre-op instructions, creating unacceptable bleeding risk. The orthopedic surgeon cancels; the ASC reports the ORIF code with modifier 73 at 50% of allowable.
A patient arrives for elective hip arthroscopy to address femoroacetabular impingement. After being positioned on the traction table and prepped but before general anesthesia is induced, the patient develops acute-onset chest pain radiating to the jaw. The team cancels the case and transfers the patient for cardiac evaluation. Modifier 73 is appended to the hip arthroscopy CPT code on the ASC claim.

Common mistakes

Where coders most often go wrong with modifier 73.

Source · Editorial brief grounded in CMS NCCI Policy Manual and cited references ↓

Appending modifier 73 to a professional (physician) claim on a CMS-1500 form—modifier 73 is strictly for facility claims; the surgeon's team should use modifier 53
Using modifier 73 when no anesthesia was ever planned for the procedure; if the case required no anesthesia, neither modifier 73 nor 74 is appropriate
Billing modifier 73 for an elective cancellation or a patient-elected postponement—only unplanned, medically threatening circumstances justify its use
Confusing modifier 73 with modifier 74: if any anesthesia was actually administered before the procedure stopped, modifier 74 applies, not modifier 73
Appending modifier 73 to add-on codes—it must attach to the primary parent procedure code only; add-on codes are ineligible
Submitting multiple procedure codes with modifier 73 on the same date of service for the same patient—only one discontinued procedure line is permitted per encounter under this modifier
Failing to document the specific extenuating clinical circumstance in the medical record; payers will deny or recoup if the chart does not clearly justify the cancellation before anesthesia

CPT codes that use modifier 73

35 orthopedic CPT codes in our reference list this modifier as applicable. Sorted by total RVU.

Source · Derived from per-code modifier guidance in our CPT reference

Showing top 12 of 35 by total RVU.

Where modifier 73 shows up

Body regions where this modifier most commonly appears in our orthopedic reference.

Foot & ankle 12 codes
Knee 7 codes
Hip 4 codes
Hand 3 codes

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01Who can bill modifier 73—the surgeon or the facility?

Only the facility (ASC or outpatient hospital) may bill modifier 73. The operating surgeon uses modifier 53 on the professional claim for a discontinued procedure. Applying modifier 73 to a physician fee-schedule claim is incorrect and will result in denial.

02How much does the facility get paid when modifier 73 is used?

Reimbursement is 50 percent of the applicable facility fee schedule amount for the primary procedure. This partial payment acknowledges the real costs—staff time, sterile supplies, room setup—incurred before the case was called off.

03What is the difference between modifier 73 and modifier 74?

The dividing line is whether anesthesia was administered. Modifier 73 applies when the procedure stops before any anesthesia is given; modifier 74 applies when the procedure stops after anesthesia has been delivered or after the procedure itself has begun (e.g., scope inserted, incision made). Modifier 74 reimburses at 100% of the facility rate.

04Can modifier 73 be used if the patient changed their mind and asked to cancel?

No. Patient-elected or elective cancellations do not qualify. The cancellation must result from an extenuating clinical circumstance or an unexpected finding that genuinely threatens patient safety. The medical record must document that specific reason.

05Does the procedure need to have required anesthesia in the first place for modifier 73 to apply?

Yes—anesthesia must have been planned for the procedure. If the scheduled service required no anesthesia at all, modifier 73 is not applicable and should not be appended, regardless of when the case was stopped.

06Can modifier 73 be placed on more than one procedure code for the same patient on the same date?

Generally, no. Most payer guidelines, including those aligned with CMS guidance, allow modifier 73 on only one procedure code per member per date of service. If part of the planned work could be described by a different completed CPT code, bill that completed code normally instead.

Sources & references

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

01CMS Medicare Claims Processing Manual, Publication 100-04, Chapter 4, Section 20.6.4 — https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/Downloads/clm104c04.pdf
02CMS NCCI Medicare Policy Manual 2025 — https://www.cms.gov/files/document/2025nccimedicarepolicymanualcompletepdf.pdf
03Novitas Solutions Modifier 73 Fact Sheet — https://www.novitas-solutions.com/webcenter/portal/MedicareJH/pagebyid?contentId=00144540
04Noridian Medicare Modifier 73 Guidance (Jurisdiction E Part B) — https://med.noridianmedicare.com/web/jeb/topics/modifiers/73
05AAPC Knowledge Center: Facility Coding for Modifiers 52, 73, and 74 — https://www.aapc.com/blog/90202-facility-coding-for-modifiers-52-73-and-74/
06AMA CPT Current Procedural Terminology and CPT Assistant (modifier guidance for discontinued procedures)

Mira AI Scribe

MODIFIER 73 — DISCONTINUED ASC PROCEDURE BEFORE ANESTHESIA Capture in the operative or pre-procedure note: (1) confirmation that the patient was fully prepped and present in the procedure room, (2) the specific clinical finding or event that threatened patient well-being, and (3) an explicit statement that no anesthesia—local, regional block, or general—had been administered at the time of cancellation. This documentation is the sole basis for payment at 50% of the facility rate. Without it, expect denial. Tag only the primary intended procedure code; do not list secondary procedures that were never initiated. This modifier is invalid on the surgeon's professional claim.

See how Mira flags modifier 73 in dictation