Glossary · Clinical

Total hip arthroplasty (THA)

Total hip arthroplasty (THA) is a surgical procedure that removes damaged bone and cartilage from the acetabulum and femoral head, replacing both with prosthetic components to relieve pain and restore hip function. It is also called total hip replacement (THR).

Verified May 8, 2026 · 8 sources ↓

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Definition

Source · Editorial summary grounded in 8 cited references ↓

In a THA, the surgeon removes the diseased femoral head and reams the acetabular surface, then implants a metal stem into the hollowed femoral canal, attaches a metal or ceramic ball to the stem, and seats a metal cup in the acetabulum secured with screws or cement. A polyethylene, ceramic, or metal liner sits between the ball and cup to create a low-friction articulating surface. The procedure is indicated for advanced joint disease—most commonly osteoarthritis—as well as avascular necrosis, femoral neck fracture, hip dysplasia, rheumatoid arthritis, and select malignancies of the joint.

Medicare coverage requires documented failure of conservative management before surgery is approved. Acceptable evidence includes a trial of NSAIDs (or a documented contraindication to them), supervised physical therapy, and chart notes confirming that activities of daily living (ADLs) remain impaired despite those efforts. Radiographic findings—joint space narrowing, subchondral sclerosis, osteophytes, subchondral cysts, or avascular necrosis—must also be on file. For atypical indications such as fracture or malignancy, supporting imaging or pathology reports are required in the medical record.

When a previously implanted THA fails—due to aseptic loosening, instability, infection, or component wear—revision surgery is performed. Revision coding is component-specific: replacing both the acetabular and femoral components carries a different CPT code than replacing only one. For infection-driven revisions, laboratory and pathology results demonstrating the infection, plus a physician attestation that proceeding with surgery is appropriate, must accompany the claim.

Why it matters

Choosing the wrong CPT code between a primary THA, a conversion from hemiarthroplasty, and a single- versus dual-component revision can shift reimbursement by thousands of dollars and trigger a medical-necessity audit. CMS Local Coverage Determinations (LCDs) require specific documentation checkpoints—failed conservative therapy, qualifying imaging, and laterality—before a claim is payable; missing any one element is a leading cause of THA claim denials and post-payment takebacks. For bilateral cases, the chart must independently justify medical necessity for each side, and the correct modifier must be appended, or the second hip will be bundled and denied.

Common mistakes

Where people most often go wrong with this concept.

Source · Editorial brief grounded in cited references ↓

Coding a conversion of hemiarthroplasty to THA as a standard primary THA (27130) instead of the appropriate revision code, because the acetabular component is being added for the first time.
Omitting laterality from the ICD-10-CM diagnosis code—payors require left, right, or bilateral specificity for joint disorders.
Appending modifier 50 (bilateral) to a second-line claim without verifying individual payer rules; some payors require two separate line items, others require a single line with modifier 50.
Failing to document a trial of conservative therapy or a specific contraindication to it, leaving the claim vulnerable to medical-necessity denial under CMS LCD requirements.
Selecting a single-component revision code (27137 or 27138) when both components are actually replaced, forfeiting reimbursement for the additional work captured under 27134.
Not including lab or pathology reports in the record when infection drives a revision, which is a hard LCD documentation requirement and a common audit finding.
Using modifier 22 (Increased Procedural Services) without detailed operative-note language explaining why the procedure was substantially more complex than typical, leading to automatic downcoding by payers.

Related codes

Codes commonly involved when this concept appears in practice.

CPT

ICD-10

M16.11 M16.12 M16.31 M16.32

Modifiers

50 Bilateral procedure 22 Increased procedural services 52 Reduced services 58 Staged or related procedure 59 Distinct procedural service LT Left side RT Right side

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 8 cited references ↓

01What is the difference between CPT 27130 and CPT 27132?

CPT 27130 covers a primary total hip arthroplasty. CPT 27132 is used when a previous hemiarthroplasty is converted to a full THA by adding an acetabular component—even though the femoral stem from the hemiarthroplasty may be retained. Using 27130 for a conversion is a common and auditable error.

02Does Medicare require proof that conservative treatment failed before approving THA?

Yes. CMS LCDs require documentation of a reasonable trial of non-surgical management—such as NSAIDs or supervised physical therapy—or a documented contraindication to those treatments. The chart must also show that ADLs remain impaired despite those efforts. Cases submitted without this documentation are routinely denied on medical-necessity grounds.

03How do I code a bilateral THA performed in the same surgical session?

Report the primary THA code twice with modifier 50 (bilateral), or as two separate line items with LT and RT modifiers, depending on payer preference. The medical record must independently support medical necessity for each hip; a single joint-disease statement covering both sides is generally insufficient under CMS LCD requirements.

04Which CPT code applies when only the acetabular liner is exchanged during a revision?

Per CPT Assistant (September 2021), exchanging only modular articular components such as the acetabular liner without removing the acetabular shell is reported as 27134-52 (revision of total hip arthroplasty, both components, with modifier 52 for reduced services). This reflects that a full component revision was not performed.

05What ICD-10-CM codes are most commonly paired with a primary THA claim?

Primary osteoarthritis of the hip (M16.11 right, M16.12 left) accounts for the majority of THA diagnoses. Avascular necrosis of the femoral head (M87.051/M87.052), post-traumatic osteoarthritis, and acute femoral neck fracture (S72.001A) are also common. Laterality specificity is required on all joint-disorder codes.

06What MS-DRG covers a primary total hip arthroplasty inpatient stay?

Primary THA without a major complication or comorbidity (MCC) typically maps to MS-DRG 470 (Major Hip and Knee Joint Replacement or Reattachment of Lower Extremity without MCC). The presence of an MCC shifts the case to MS-DRG 469, which carries significantly higher reimbursement.

Sources & references

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

Mira AI Scribe

When Mira detects a THA encounter, it will prompt for the following documentation elements before finalizing the note and code selection: 1. LATERALITY — Confirm left, right, or bilateral. Required for ICD-10-CM specificity and modifier assignment. 2. PRIMARY vs. REVISION — If any prior hip implant exists (including hemiarthroplasty), flag for revision pathway. Identify which components (acetabular only → 27137; femoral only → 27138; both → 27134). 3. CONSERVATIVE THERAPY FAILURE — Capture NSAID trial with duration, or documented contraindication, AND supervised PT or documented reason PT was not appropriate. ADL impairment despite treatment must be explicit. 4. IMAGING — Confirm qualifying radiographic or advanced imaging findings are referenced in the note (joint space narrowing, osteophytes, subchondral changes, AVN, or fracture). 5. COMORBIDITY RISK DOCUMENTATION — If the patient has significant comorbidities, the note must reflect a risk-benefit discussion for non-cardiac surgery. 6. INFECTION-DRIVEN REVISION — If infection is the revision indication, Mira will flag that lab/pathology results and a physician attestation to proceed must be linked in the chart before claim submission. 7. BILATERAL CASES — Mira will prompt for independent medical necessity documentation for each hip and verify payer-specific bilateral modifier rules before code finalization. 8. MODIFIER 52 ALERT — For revision arthroplasty involving only modular articular components (e.g., head and liner swap without stem removal), Mira will suggest 27134-52 per CPT Assistant guidance (Sept. 2021, Vol. 31, Issue 9).

See Mira's approach

Related terms

Hemiarthroplasty Clinical

Hemiarthroplasty is a partial joint replacement in which only one articular surface is resurfaced with a prosthesis—most commonly the femoral head in the hip or the proximal humerus in the shoulder—while the native opposing surface is left intact.

Medical necessity Compliance

Medical necessity is the standard requiring that a service or item be reasonable and appropriate for diagnosing or treating a patient's condition according to accepted clinical practice. Payers—including Medicare—use this standard to determine whether a claim will be covered and paid.

Local Coverage Determination (LCD) Compliance

A Local Coverage Determination (LCD) is a regional Medicare policy issued by a Medicare Administrative Contractor (MAC) that defines when a specific service, procedure, or supply is considered reasonable and medically necessary within that contractor's jurisdiction.