Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
NPIDirectory

Nicholas Maassen

Individual provider Orthopaedic Surgery Physician · NPI 1477718302

Nicholas Maassen practises Orthopedic Surgery in Chicago, Illinois. Graduated from University of Wisconsin School of Medicine in 2008, 18 years ago. Practices with The University of Chicago Medical Center, a 909-clinician group and accepts Medicare assignment. Licensed in Illinois.

Years since qualifying
18
Trained at
University of Wisconsin School of Medicine
Licensed in
IL
In the registry since
2008
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Practice location Address checks out

5841 S Maryland Ave
Chicago, IL 60637-1443
Phone: (888) 824-0200
Show map & directions

Directions in Google Maps · Apple Maps · OpenStreetMap

Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Orthopaedic Surgery Physician (primary) Taxonomy 207X00000X · Licence 036152536 (IL)

Record details

NPI number1477718302
Entity typeIndividual (Type 1)
GenderMale
Sole proprietorNo
NPI enumeratedJuly 21, 2008
Last updated in NPPESOctober 24, 2022

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyORTHOPEDIC SURGERY
Medical schoolUNIVERSITY OF WISCONSIN SCHOOL OF MEDICINE
Graduated 2008 (18 years in practice)
Group practice The University Of Chicago Medical Center — 909 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations2 on file with Medicare

Procedures

From CMS Care Compare, which counts the procedures a clinician billed to Original Medicare and Medicare Advantage over a recent 12-month period. CMS reports a fixed list of common procedures, so this is not everything the clinician does. Counts of 10 or fewer are given as a range, because CMS withholds small numbers.

Upper limb (arm) arthroscopy (minimally invasive joint repair) 11 times · 46th percentile
Removal of tissue 1–10 times

The percentile compares how often this clinician performed the procedure with other clinicians who performed it, as CMS calculates it. It measures volume, not outcomes or skill.

Medicare patients and services, 2024

From the CMS Medicare Physician & Other Practitioners file for calendar year 2024. It counts Original Medicare patients only, so a practice that mostly sees Medicare Advantage or privately insured patients looks smaller here than it is.

Medicare patients244
Services billed 643 a service is one billed item, such as a visit, a test or a procedure
Average patient age71

Dollar amounts are not shown. What Medicare pays a practice is gross billings, before staff, premises and tax and including the cost of any drugs it administers, so it is not what a clinician earns.

Payments from drug and device companies, 2025

Drug and device makers are required by federal law (the Physician Payments Sunshine Act) to report what they pay or give to clinicians, and CMS publishes the reports as Open Payments. This is the 2025 program year. A report is a record of a payment, not an allegation of anything, and many are small items such as meals. Only general payments are listed here; research payments and ownership or investment interests are reported separately by CMS and are not shown.

Consulting Fee $5,150 3 payments
Food and Beverage $356 4 payments · a meal or drink at a meeting or visit, not a fee

Each amount is the sum of what companies reported for that kind of payment in 2025, rounded to the dollar. Not all of it is income to the clinician: a meal is not a fee, a charitable contribution goes to a charity, and a royalty or an acquisition payment is not a salary.

Check a report, or dispute one, at the source in CMS’s own tool, Open Payments. Corrections go through CMS’s dispute process. This site removes a home address on request and asks for no proof, because that is privacy; it will not remove an accurate payment report on request, because that is a statutory public disclosure.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at The University of Chicago Medical Center

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 909 clinicians in the practice; 12 are shown here.

Other providers in Chicago