CPT Code 73521: Bilateral Hip X-Ray, 2 Views Billing Guide

Key Takeaways

CPT code 73521 describes a bilateral hip radiographic examination with pelvis when performed, requiring exactly 2 views per the AMA CPT codebook.

73521 is the lowest view-count code in the bilateral hip series; use 73522 for 3-4 views and 73523 for 5 or more views.

View-counting when a pelvis AP is acquired alongside bilateral hips is contested; follow AMA CPT Assistant June 2016 guidance and verify payer policy before billing.

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Bilateral hip X-rays are among the most frequently ordered musculoskeletal studies in orthopaedic and radiology practices, yet selecting the correct code from the 73521-73523 series trips up even experienced coders. CPT code 73521 is specific: two views, bilateral hips, with the pelvis captured when clinically indicated. Bill one view too few or forget to document the pelvis separately, and you face a denial or a post-payment audit.

This reference guide covers the CPT code 73521 descriptor, view-counting rules (including the contested pelvis AP question), modifier usage for split-billing, related codes, ICD-10 diagnosis pairings, Medicare reimbursement context, and portable X-ray supplier requirements under Noridian guidelines.

CPT code 73521: official descriptor and clinical context

The American Medical Association (AMA) defines CPT code 73521 as:

• Radiologic examination, hips, bilateral, with pelvis when performed; 2 views. Three details in that descriptor matter for correct billing.
• Bilateral: Both hips are imaged in a single session. This is a distinct series from the unilateral codes 73501-73503.
• With pelvis when performed: The pelvis AP is optional clinically, not required. When it is acquired, it is reported as part of 73521, not as a separately billable pelvis code.
• 2 views: Exactly two views must be documented to support 73521. One view routes to the unilateral series; three or more views trigger an upgrade to 73522 or 73523.

Codes 73500-73540 were deleted effective January 1, 2016. The AMA replaced them with six new codes: 73501-73503 for unilateral hip exams and 73521-73523 for bilateral hip exams. This restructuring, reported in Radiology Today (January 2016), aligned hip X-ray coding with the view-count model already used for other musculoskeletal imaging series.

Orthopaedic surgeons, radiologists, chiropractors, and sports medicine practices that perform standing bilateral hip studies routinely use this code. For practices managing chiropractic billing workflows, understanding the 2016 restructuring is essential to avoid submitting retired codes that payers will automatically reject.

View-counting rules for CPT code 73521

The most common source of coding errors in the 73521-73523 series is miscounting views. The rules below reflect the AMA CPT Assistant guidance from June 2016, which remains the definitive reference when payer policies are silent on the issue.

Does the pelvis AP count as one of the two views?

This is the most contested question in bilateral hip coding. The AMA CPT Assistant (June 2016) states that when a bilateral hip X-ray is medically indicated, it is appropriate to report a bilateral hip X-ray CPT code such as 73521-73523. The guidance does not explicitly resolve whether the pelvis AP counts as one of the numbered views.

In practice, AAPC forum discussions and the Ask Dr. Z May 2024 radiology coding Q&A show coders split across three interpretations:

• Interpretation A: AP pelvis + one lateral hip = 2 views total, supporting 73521.
• Interpretation B: AP pelvis + bilateral laterals = 3 views total, supporting 73522.
• Interpretation C: AP and lateral per hip (no separate pelvis count) = 4 views total, supporting 73522.

Because payer policies vary, verify your MAC’s local coverage determination before finalising your view-count approach. Document exactly which projections were taken and their clinical rationale. Consistent internal documentation reduces audit exposure significantly. For physical therapy and orthopaedic practices that routinely order bilateral studies, a written protocol aligned to your MAC’s guidance protects against retrospective claim adjustments.

Modifiers for CPT code 73521: 26, TC, and 59

Three modifiers appear regularly on 73521 claims. Applying them incorrectly is one of the fastest routes to a denial or a post-payment audit.

Modifier 26 and TC: professional and technical component split

When a radiologist interprets a study ordered at a hospital or outpatient facility, the global service is typically split between a technical component (equipment, film, technologist) and a professional component (physician interpretation and report). Bill CPT code 73521-26 for the professional component only. Bill CPT code 73521-TC for the technical component only. When both are provided by the same entity (a freestanding imaging center), report 73521 globally without a modifier.

Modifier 59: distinct procedural service

Modifier 59 signals to the payer that CPT code 73521 is a distinct service, not part of another procedure performed on the same date. The Centers for Medicare and Medicaid Services (CMS) considers modifier 59 high-risk for misuse. Append it only when the bilateral hip study is genuinely separate from other imaging performed during the same encounter and when the clinical record clearly supports that separation. Payers may request documentation before reimbursing claims with modifier 59 appended. A related review of CPT modifier strategies across procedure types shows that over-reliance on modifier 59 frequently triggers pre-payment review.

NCCI edits and bundling considerations

The National Correct Coding Initiative (NCCI) edits govern which codes may be billed together on the same date of service. For CPT code 73521, the primary bundling concern arises when a provider also bills a separate pelvis code (such as 72170 or 72190) on the same date. Because the 73521 descriptor already includes the pelvis “when performed,” a separately billed pelvis study on the same date is likely to be bundled and denied unless the clinical record documents a distinct medical necessity for two separate studies.

Similarly, billing 73501 (unilateral hip, one view) alongside 73521 on the same date will typically trigger an NCCI edit because the bilateral code already encompasses both sides. Use the CMS Physician Fee Schedule lookup tool to verify current NCCI edit pairs before submitting claims where multiple hip or pelvis codes appear on the same claim line.

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ICD-10 diagnosis codes commonly paired with CPT code 73521

Medical necessity for bilateral hip imaging must be supported by an ICD-10-CM diagnosis code that justifies the bilateral approach. Unilateral diagnoses will generally not support a bilateral hip code. Below are the most common pairings.

Document the specific bilateral indication in the ordering provider’s notes. Payer medical necessity reviewers look for direct correlation between the diagnosis code and the bilateral nature of the study. Sports medicine and sports medicine practices ordering bilateral hip studies for athletes should document whether comparative imaging is part of the clinical protocol.

Medicare reimbursement for CPT code 73521

Medicare reimbursement for CPT code 73521 is calculated using the Resource-Based Relative Value Scale (RBRVS). Rates vary by locality and are updated annually in the CMS Physician Fee Schedule. There is no single national rate that applies in all geographies.

To find the current rate for your locality, use the FastRVU 2026 RVU lookup tool, which imports CMS fee schedule data and applies locality conversion factors. Alternatively, use the CMS PFS search tool directly. The global payment (no modifier) is higher than the TC-only or 26-only rates, which are calculated as a fraction of the global.

Key billing facts that affect reimbursement for CPT code 73521 on Medicare claims:

• The procedure is subject to the multiple procedure payment reduction (MPPR) for diagnostic imaging when two or more imaging services are provided on the same date by the same provider.
• The global period is 0 days (XXX indicator), meaning no post-procedure restrictions apply to subsequent services.
• Fluoroscopy used incidentally during the study does not create a separate billable service under Medicare.
• Always verify the current fee schedule year when quoting rates to patients or payers; rates change each January 1.

For practices managing claims management across multiple payers alongside Medicare, compare allowable amounts carefully. Commercial payers may reimburse above or below the Medicare allowable depending on contract terms. Tracking these variances helps identify underpaid claims worth appealing. Related CPT reference guides for practices billing across multiple imaging types include our IVF CPT code guide for fertility imaging workflows.

Portable X-ray supplier requirements for CPT code 73521

Portable X-ray suppliers who transport equipment to a patient’s location (nursing facility, home health setting) must follow specific Medicare billing rules when reporting CPT code 73521. According to Noridian Medicare (JE Part B) portable X-ray billing guidelines, transportation HCPCS codes R0070 or R0075 must be billed alongside CPT codes in the 73521-73522 range whenever portable equipment is physically transported to the imaging location.

No transportation charge is payable unless the portable X-ray equipment was actually transported to the location where the X-ray was taken. Key distinctions between the two HCPCS codes:

• R0070: Transportation of portable X-ray equipment and personnel to home or nursing facility, one patient seen.
• R0075: Transportation of portable X-ray equipment and personnel to nursing facility, per trip (more than one patient seen).

Portable X-ray suppliers who omit transportation codes when billing 73521 may face claim denials. Those who bill R0075 when only one patient was seen face overpayment recovery. Document patient count per transport trip in your billing records. For practices using digital documentation workflows, building a portable X-ray billing checklist into your intake process reduces these errors at the point of service rather than during claim review.

Conclusion

Most bilateral hip billing errors come down to two things: miscounting views and mismatching diagnosis codes. CPT code 73521 requires exactly two views, bilateral, and the pelvis component is bundled when acquired. Upgrade to 73522 or 73523 when view counts increase, and verify your MAC’s guidance on pelvis AP counting before locking in your protocol.

Pabau’s claims management software helps orthopaedic and radiology billing teams build code-specific documentation checklists, flag modifier conflicts before submission, and track denial patterns by CPT code. Book a demo to see how it works for your billing team.

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