Quick answers
- Which hospitals does Denis O Brien work at?
- Medicare's official clinician data lists Denis O Brien at 1 hospital: MedStar Montgomery Medical Center. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does Denis O Brien see patients?
- Medicare's clinician data lists 4 practice locations, including Frederick, MD, Olney, MD and Silver Spring, MD. Call before your visit to confirm the address.
- What is Denis O Brien's specialty?
- Medicare lists Orthopedic Surgery as the primary specialty.
- Does Denis O Brien accept Medicare assignment?
- Yes. Medicare's clinician data says Denis O Brien accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- What is the phone number for Denis O Brien?
- (301) 774-0500, as listed in official Medicare / NPI Registry data.
- What is Denis O Brien's NPI number?
- 1427053339. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Hospitals where Denis O Brien works
Medicare's Facility Affiliation Data lists Denis O Brien at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- MedStar Montgomery Medical CenterOlney, MD · Acute Care Hospital · CCN 210018
Practice locations
Addresses where Denis O Brien is enrolled with Medicare (CMS data updated 2026-10-02).
- 187 Thomas Johnson DrFrederick, MD 21702
- 187 Thomas Johnson Dr, Suite 6Frederick, MD 21702
- 3414 Olandwood CtOlney, MD 20832 (301) 774‑0500
- 3801 International DrSilver Spring, MD 20906 (301) 598‑9715
Group practices
Medicare enrollment lists Denis O Brien as a member of these groups (CMS data updated 2026-10-02).
- Centers for Advanced Orthopaedics LLC604 clinicians in the group
- Amber Hill Physical Therapy Inc334 clinicians in the group
Specialties
- Orthopedic Surgeryprimary
Other orthopedic surgeons in Frederick
Clinicians with the same Medicare primary specialty in Frederick, MD — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | Georgetown University School Of Medicine |
| Graduation year | 1983 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1427053339 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated 2026-10-02, retrieved 2026-10-29
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians