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This page describes products and general use; it is not medical advice.
A Trömner reflex hammer (also written Tromner) is a two-headed percussion hammer used by clinicians to elicit reflexes. In US regulation it is not a separate device type: it falls under the FDA product category “percussor”, a Class I device.
What a Trömner reflex hammer is
The Trömner hammer is one of several named reflex hammer styles. It is described as shaped like a two-headed mallet, with a larger head used for tendon stretch reflexes and a smaller head used for percussion myotonia; the design is credited to Ernst Trömner (Wikipedia, “Reflex hammer”, a secondary source). The names “Trömner hammer”, “Tromner hammer” and “Tromner reflex hammer” all refer to this style.
Who uses it: physicians and other clinicians who perform neurological examinations, and students learning the examination. For the other common styles, such as Taylor, Queen Square and Babinski, see our guide What Is a Reflex Hammer?.
How FDA classifies it
FDA regulates reflex hammers under 21 CFR 882.1700. The regulation (checked 2026-10-30) defines a percussor as “a small hammerlike device used by a physician to provide light blows to a body part.” A Trömner hammer fits that description, so the same classification applies to it as to other reflex hammer styles.
| Item | What the FDA record states | Source |
|---|---|---|
| Device name | Percussor | FDA Product Classification, code GWZ |
| Regulation | 21 CFR 882.1700 (Neurological devices, diagnostic) | eCFR |
| Device class | Class I (general controls) | eCFR; FDA classification database |
| Premarket notification | Exempt from 510(k), subject to the limitations in 21 CFR 882.9 | eCFR |
| Quality system | Exempt from the quality management system regulation (part 820) except for the records and complaint file requirements | eCFR |
| Review panel | Neurology | FDA classification database |
| Implanted or life-sustaining | No for both | FDA classification database |
In practice this means a manufacturer of a reflex hammer does not need a 510(k) clearance to market it in the US, but remains subject to general controls such as establishment registration and the records and complaint file requirements named above.
Safe use and handling basics
A percussor is defined as a device for light blows to a body part, so it is a hand-held tool rather than a powered one. Care and handling instructions come from the manufacturer of the specific hammer; they vary by model and are not set by the FDA classification.
Common mistakes
- Treating “Trömner” as a separate regulated device. FDA lists reflex hammers together under the percussor category, code GWZ.
- Reading “510(k) exempt” as “unregulated”. The device is Class I and still falls under general controls.
Where reflex hammers fit among exam supplies
Clinics that stock neurological examination tools often group reflex hammers with other diagnostic instruments; see diagnostic, monitoring and imaging supplies. Related examination tools we cover include the Wartenberg pinwheel and the 128 Hz tuning fork.
FAQ
What is a Trömner hammer?
It is a two-headed mallet-style reflex hammer, attributed to Ernst Trömner, with a larger head for tendon stretch reflexes and a smaller head for percussion myotonia.
Is Tromner the same as Trömner?
Yes. “Tromner” is the spelling without the umlaut; both refer to the same hammer style.
Does FDA clear Trömner hammers?
FDA classifies reflex hammers as percussors, Class I, exempt from premarket notification (510(k)) under 21 CFR 882.1700, so no individual clearance is required.
Sources
- 21 CFR 882.1700 Percussor, eCFR: https://www.ecfr.gov/current/title-21/section-882.1700 (checked 2026-10-30).
- FDA Product Classification, code GWZ: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpcd/classification.cfm?id=GWZ (checked 2026-10-30).
- Wikipedia, “Reflex hammer” (secondary source for the design description): https://en.wikipedia.org/wiki/Reflex_hammer (checked 2026-10-30).
