Written and maintained by CASRAI Editorial Board
Last updated
General product and regulatory information only. This page is not medical advice and does not describe surgical technique.
Short answer
TORP stands for total ossicular replacement prosthesis: an implantable device that, in the words of 21 CFR 874.3495, is intended for the total functional reconstruction of the ossicular chain and facilitates the conduction of sound waves from the tympanic membrane to the inner ear. A PORP (partial ossicular replacement prosthesis) is the related device for reconstructing segments of the chain. FDA regulates them under two separate sections, product codes ETA (TORP) and ETB (PORP), both Class II.
Definition and scope
The ossicular chain is the series of small middle-ear bones that carries sound from the tympanic membrane to the inner ear. When part or all of that chain cannot do this job, a prosthesis can be used in its place. FDA defines two device types for this purpose:
- Total ossicular replacement prosthesis (TORP): intended for the total functional reconstruction of the chain (21 CFR 874.3495).
- Partial ossicular replacement prosthesis (PORP): intended for the functional reconstruction of segments of the chain (21 CFR 874.3450).
The words partial and total in each name come straight from these regulatory definitions: the distinction is how much of the chain the device is intended to reconstruct. This page covers what the devices are and how they are classified and compared in the literature. Choosing a device for a patient is a clinical decision for a surgeon and is outside its scope.
How TORP and PORP are classified by FDA
A common mix-up is to treat both devices as falling under one regulation. They do not. The two sections of 21 CFR Part 874 (ear, nose and throat devices) are separate, and openFDA’s device classification database lists a separate product code for each. The table below is built from the regulation text and the openFDA classification records, checked 2026-10-30.
| Item | TORP | PORP |
|---|---|---|
| openFDA device name | Replacement, Ossicular Prosthesis, Total | Prosthesis, Partial Ossicular Replacement |
| Product code | ETA | ETB |
| Regulation | 21 CFR 874.3495 | 21 CFR 874.3450 |
| Device class | Class II | Class II |
| Intended for | Total functional reconstruction of the ossicular chain | Functional reconstruction of segments of the ossicular chain |
| Materials named in the regulation | Polytetrafluoroethylene, polytetrafluoroethylene with vitreous carbon fibers composite, porous polyethylene, or a combination | Stainless steel, tantalum, polytetrafluoroethylene, polyethylene, polytetrafluoroethylene with carbon fibers composite, absorbable gelatin material, porous polyethylene, or a combination |
openFDA also lists two related ossicular product codes, both Class II and both listed under 21 CFR 874.3450: LBM (Porous Polyethylene Ossicular Replacement) and LBP (Replacement, Ossicular (Stapes) Using Absorbable Gelatin Material). Because they carry their own codes, a database search for only ETA or ETB will not return these records. For background on how FDA device classes and submissions work, see FDA’s 510(k) and De Novo submission template, what a medical device is and the Medical Device Amendments of 1976.
TORP vs PORP: what the evidence comparison shows
One published head-to-head synthesis is Yu et al., “PORP vs. TORP: a meta-analysis”, European Archives of Oto-Rhino-Laryngology 2013;270(12):3005-17 (PMID 23400405). It pooled 40 studies with 4,311 subjects. Reading its numbers correctly matters more than the headline:
| Comparison | Combined risk ratio (95% CI) | Authors’ reading |
|---|---|---|
| Overall effectiveness | 1.28 (1.17-1.41) | Significant difference; effectiveness of PORP was higher than TORP |
| Staged-procedure subgroup | 1.13 (0.60-2.11) | No notable difference |
| Cholesteatoma subgroup | 2.60 (0.20-36.21) | No notable difference |
| Long-term stability | 0.37 (0.16-0.85) | Significant; stability of PORP superior to TORP in long-term follow-up |
| Stability, total sample | 0.64 (0.40-1.03) | No significant difference |
Two points help in interpreting this. First, a risk ratio is meaningful only alongside its confidence interval: a ratio of 2.60 sounds large, but an interval of 0.20-36.21 is compatible with no difference at all, which is why the authors call that subgroup result not notable. Second, a pooled result across published studies describes the group of studies, so it does not show that one device performs better in any particular patient. The reasons for such caveats are covered in subgroup and sensitivity analysis in meta-analysis and the entry on meta-analysis.
Where it matters for labs, clinics and supply decisions
- Use the right regulation and product code. Records, device-database searches and regulatory files for a TORP belong under ETA and 21 CFR 874.3495, and for a PORP under ETB and 21 CFR 874.3450. Citing 874.3450 for a TORP is an error.
- Read materials from the regulation and the labeling. The materials listed differ between the two regulations, as in the table above, so the regulation’s list is the starting point for a materials check against a specific product’s labeling.
- Separate regulatory status from performance. Class II classification describes how FDA regulates the device type; it is not a comparison of outcomes. Outcome comparisons come from studies such as the meta-analysis above.
Common misunderstandings
“PORP and TORP are the same regulation”
They are not. PORP is 21 CFR 874.3450 (ETB); TORP is 21 CFR 874.3495 (ETA).
“The meta-analysis proves PORP is better”
The authors report higher pooled effectiveness for PORP overall, but two subgroups showed no notable difference, and the total-sample stability comparison was not significant. It is a pooled comparison of published studies, not a ruling that applies to an individual case.
“TORP and PORP are interchangeable terms”
They name different device types defined by how much of the ossicular chain they are intended to reconstruct.
FAQ
What does TORP stand for?
Total ossicular replacement prosthesis.
What does PORP stand for?
Partial ossicular replacement prosthesis.
PORP vs TORP: what is the difference?
By FDA definition, a PORP is intended for reconstruction of segments of the ossicular chain and a TORP for total reconstruction of the chain. They have separate regulations, product codes (ETB and ETA) and listed materials; both are Class II.
What FDA class is a TORP?
Class II, product code ETA, under 21 CFR 874.3495.
Sources
- 21 CFR 874.3495, Total ossicular replacement prosthesis: https://www.law.cornell.edu/cfr/text/21/874.3495 (checked 2026-10-30).
- 21 CFR 874.3450, Partial ossicular replacement prosthesis: https://www.law.cornell.edu/cfr/text/21/874.3450 (checked 2026-10-30).
- openFDA device classification database, product codes ETA, ETB, LBM, LBP: https://api.fda.gov/device/classification.json?search=product_code:ETA (checked 2026-10-30).
- Yu H et al. PORP vs. TORP: a meta-analysis. Eur Arch Otorhinolaryngol 2013;270(12):3005-17: https://pubmed.ncbi.nlm.nih.gov/23400405 (checked 2026-10-30).
