Radiographic bone length study measuring and comparing lower extremity bone lengths, typically performed to quantify limb length discrepancy.

Verified May 8, 2026 · 6 sources ↓

Medicare: $46.43
Total RVUs: 1.39
Global, days
Region: Foot & ankle

Drawn from CMSAAPCZhealthpublishing

Documentation requirements

What must appear in the operative or office note to support the claim.

Source · Editorial brief grounded in 6 cited references ↓

Clinical indication for the study (e.g., limb length discrepancy, pre-op TKA/THA planning, growth disorder, post-fracture malunion)
Ordering provider name and documented order for the bone length study
Radiology report with measurement values for each bone segment examined and calculated discrepancy
Identification of which extremity or bilateral structures were imaged
Distinct clinical indication documented separately if billing any additional same-day lower extremity x-ray codes alongside 77073
Number and type of radiographic views obtained in the series

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

26 Professional component 52 Reduced services 59 Distinct service 76 Repeat, same physician 77 Repeat, another physician LT Left side RT Right side

What this code covers

Source · Editorial summary grounded in 6 cited references ↓

CPT 77073 covers a series of radiographic images taken specifically to measure and compare bone lengths — most commonly the femur, tibia, and fibula bilaterally — to quantify limb length discrepancy (LLD). It is ordered for pre-operative TKA or THA planning, pediatric growth monitoring, post-fracture malunion assessment, and congenital or developmental limb anomalies. The study inherently includes all radiographic imaging of the lower extremities obtained in the course of that measurement; you cannot separately bill lower extremity x-ray codes (e.g., 73560, 73562, 73503) for the same films used in the bone length study.

NCCI Policy Manual (updated 1/1/2026) is explicit: lower extremity radiograph codes are bundled into 77073 and cannot be unbundled simply because a knee or hip x-ray was taken the same day. The exception is narrow — a separate and distinct radiologic examination with additional films taken to evaluate a different clinical problem may be reported alongside 77073 using an NCCI PTP-associated modifier (modifier 59 on the additional x-ray code). Same-day knee films ordered solely for TKA pre-op planning alongside leg length studies present a gray zone; document distinct clinical indications for each service if billing both.

The code carries a global period of XXX, meaning it has no pre- or post-operative global days. It is billed most frequently by diagnostic radiology and orthopedic surgery. The professional component (interpretation only) is billed with modifier 26 when the reading physician does not own the equipment; the technical component is billed with modifier TC by the facility. Orthopedic practices that own their imaging equipment bill the global service without either split-billing modifier.

RVU & reimbursement

Component RVUs and Medicare national rate. Actual payment varies by GPCI locality.

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	0.25
Practice expense RVU	1.11
Malpractice RVU	0.03
Total RVU	1.39
Medicare national rate	$46.43
Global period	days

Payment by site of service

Medicare pays different rates by setting. HOPD typically pays substantially more than ASC for the same procedure.

Source · CMS OPPS Addendum B·ASC HCPCS payment rates·2026

Setting	Medicare rate (national)
Office (PFS non-facility) Procedure performed in physician's office	$46.43
HOPD (APC 5522) Hospital outpatient department	$106.81

Common denial reasons

The recurring reasons claims for CPT 77073 get rejected.

Source · Editorial brief grounded in CMS NCCI edits, AAOS coding appeals, and cited references ↓

Unbundled lower extremity x-ray code (e.g., 73560, 73562, 73503) billed same-day without modifier 59 and a distinct clinical indication — NCCI PTP edit fires
Missing or vague clinical indication in the order or report (e.g., no diagnosis code supporting LLD or pre-op planning)
Individual radiographic images from the bone length series billed separately in addition to 77073 — explicitly prohibited by NCCI policy
Modifier 26 or TC omitted when the professional and technical components are split between a reading physician and a facility
Lack of documented measurements in the radiology report, causing medical necessity denial on post-payment review

Frequently asked questions

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

01Can I bill knee or hip x-rays the same day as 77073?

Only if the x-rays were taken for a distinct clinical problem using additional films — not the same images used in the bone length study. Append modifier 59 to the x-ray code (e.g., 73562-59) and document separate indications for each service. If the knee films and the leg length study are both for TKA pre-op planning, the clinical distinction is weak and denial risk is high.

02Does 77073 cover both legs, or do I bill it twice for bilateral studies?

77073 covers the bilateral study as a single service. Do not bill two units or append modifier 50. The study inherently compares both lower extremities; billing it twice would trigger an MUE edit.

03When should I use modifier 26 versus billing the global code?

Use modifier 26 when the interpreting physician does not own or operate the imaging equipment — common in hospital or independent imaging center settings. Bill the global code (no modifier) only when a single provider or group owns the equipment and performs the interpretation. The facility bills modifier TC for the technical component when split billing applies.

04What ICD-10 codes commonly support 77073?

M21.761/M21.762 (unequal limb length, femur), M21.769 (unequal limb length, unspecified), Q72.891/Q72.892 (congenital limb deficiency, lower limb), and Z96.641/Z96.642/Z96.649 (presence of right/left/unspecified knee joint implant) for post-arthroplasty limb length assessment are frequently used. Payers may also accept Z47.89 (encounter for other orthopedic aftercare) in the post-surgical context.

05Is 77073 payable in a physician office setting?

Yes, but only if the practice owns the x-ray equipment and the interpreting physician bills globally. If images are sent out for interpretation, bill modifier 26 for the read only. Office-based payment rates differ from HOPD rates — see the Site of Service comparison on this page.

06Can I bill 77073 with 77075 (bone survey) on the same date?

No. 77075 includes radiologic examination of all bones, and 77073 is bundled under that umbrella when both are performed the same day. NCCI policy prohibits separately reporting individual bone studies when a complete survey is performed.

Sources & references

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

Mira AI Scribe

Mira's AI scribe captures the clinical indication for the bone length study directly from dictation — limb length discrepancy measurement, pre-operative TKA or THA planning, or growth assessment — and flags whether any same-day lower extremity x-rays were ordered for a separate clinical problem. That distinction is what justifies modifier 59 on the companion x-ray code and prevents an NCCI PTP denial from bundling those films into 77073.

See how Mira captures CPT 77073 documentation