Aetna CO-45 Contractual Adjustments in Orthopedics
Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement. Copy-paste appeal letter with documented overturn rate and attachment checklist for Aetna in Orthopedics.
Verify before filing
Filing deadlines, appeal addresses, and policy criteria in this template reflect typical payer behavior at publication. Aetna updates policies frequently and plan-level rules vary by employer group, state, and line of business. Always cross-check the specific deadline and filing address on your EOB, and confirm current Aetnamedical-policy language through the payer’s provider portal before submitting an appeal. Overturn-rate language below reflects AAPC-reviewer consensus, not payer-published statistics.
When to use this template
Aetna CO-45 in orthopedics is usually a valid contractual write-off. Orthopedic procedures (TKA, THA, arthroscopy, spine surgery) have large dollar amounts, so the CO-45 dollar values look scary even when the percentage is normal.
Attachment checklist
- Ordering provider note with clinical indication
- Prior workup or conservative-care documentation
- Payer medical policy reference citing met criteria
- Retroactive authorization request (if applicable)
Missing any one of these is the single largest cause of appeal denials. Build a pre-filing checklist before you submit.
Copy-paste letter template
Swap in your patient details at every [bracketed field]. Attach the documentation listed above. Submit within 180 days of the original adjudication.
[Payment dispute, not clinical appeal] [Practice Letterhead] [Date] Aetna Provider Relations Re: Payment Dispute. CO-45 Fee Variance Provider: [Practice, NPI, TIN] Contract: [ID / Effective] Dispute Period: [Date range] CPT Affected: [e.g., 27447 TKA] Dear Provider Relations: We are disputing the allowed amount on the following orthopedic claims where CO-45 variance appears inconsistent with our contracted rate. Contracted rate: CPT 27447 TKA = $[X] per-procedure, or case rate of $[Y] per episode per contract dated [date]. Disputed claims: 1. Claim [#], DOS [date]: Allowed $[A] vs expected $[X or Y] 2. [Additional claims] Root Cause Analysis: [Identified root cause, e.g., "Aetna's claim system applied out-of-network fee schedule; network status on EOB is in-network", or "Case-rate contract not applied; claim paid per-procedure basis", etc.] Documentation attached: 1. Contract excerpt showing rate 2. EOBs for disputed claims 3. Network verification (provider enrollment letter) Respectfully request adjustment. Sincerely, [Practice Administrator]
Investigate only when the CO-45 variance is unusually large or inconsistent across claims. Routine CO-45 adjustments are valid contractual write-offs and should not be appealed.
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Related templates
Same code, different payer. Or same payer, different problem
Want the full playbook for this scenario?
The complete playbook page covers why Aetna throws CO-45 specifically in orthopedics, the exact fix workflow, filing deadlines, high-risk CPTs, and FAQs. Plus this same copy-paste letter.
Read the full playbookCommon questions on this template
How long do I have to file a CO-45 appeal with Aetna?
180 days from the initial adjudication date for most Aetna plans. Corrected claims (for administrative fixes like missing modifiers or auth numbers) have a different and usually longer window. Always confirm the specific deadline on the EOB for your claim.
What is the typical overturn rate for this denial type?
65-80 percent when a clear contract-rate mismatch is documented. Success depends heavily on documentation completeness and whether the clinical criteria in Aetna's medical policy are matched point-by-point in the appeal.
Should I file this as a corrected claim or a formal appeal?
CO-45 denials are usually formal clinical appeals. The template below follows the formal-appeal structure. Use a corrected claim only if the fix is administrative (a missing modifier, wrong NPI) rather than clinical.
Can I reuse this template for other payers?
The structure works for any payer, but the filing address, deadline, and policy references are specific to Aetna. Check our other templates for payer-specific versions; we have 50+ payer/code combinations in the directory.
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