The denominator is the argument
Per-case cost has two fields, not one. The numerator is a price. The denominator is how many uses you are allowed to get out of that price.
On the single-use side the denominator is 1, and there is nothing to discuss. On the reusable side the denominator is a document — a validated reprocessing cycle count — and essentially everything interesting in this comparison lives in how that number was arrived at. Change it by a factor of four and the conclusion flips. Change it by a factor of ten and the flip stays invisible for a year, because no spreadsheet has a column for the assumption.
Calling it a count is part of the trouble. A specification is a designed value with a tolerance around it; a reuse count is neither. It is an empirical claim about how many reprocessing cycles a fiber survives while still doing its job — and “still doing its job” is the soft half of that sentence, because it depends on who is judging and against what.
What a multicentre study actually measured
The best available field data on reusable fibers is not a datasheet. It is a prospective multicentre study that ran 541 ureteroscopic procedures across 37 reusable holmium delivery fibers from four commercial models, all bought new off the shelf, recording pulse energy, frequency and total energy delivered for every case.
Mean uses per fiber: 14.6. The mean is not the finding. This is:
| Fiber (core diameter) | Mean uses per fiber | Standard error |
| 200 µm | 3.0 | ± 0.4 |
| 270 µm | 12.8 | ± 2.44 |
| 365 µm (model A) | 21.3 | ± 7.12 |
| 365 µm (model B) | 28.7 | ± 6.69 |
Four products, all marketed as reusable, all used by competent endourologists in the same study protocol. The longest-lived of the four outlasted the shortest by a factor of 9.6. Stratified by core size, 365 µm fibers averaged 23.5 uses against 11.3 for 270 µm — a factor of two from the core diameter alone.
Two things follow from that table. The first is that “reusable” is a category, not a specification. A purchasing line that reads reusable fiber, qty 200 has not told you the denominator; it has told you which shelf it came off.
The second is that the denominator is a function of the fiber’s geometry, not of how careful your department is. The reason is the same one that governs everything else at a fiber tip: energy density at the launch face scales with the inverse square of the core diameter, so a 270 µm fiber is running roughly twice the irradiance of a 365 µm fiber at identical settings, doing more work per unit area at the face it eventually has to survive. Its expected life is shorter for a reason that has nothing to do with handling.
The retirement rule is worth reading closely, because it tells you what the count measures. After each case a fiber was kept or retired on three observations: visual inspection for overt damage, whether the aiming beam was still transmitting, and overall length. All three are user-side checks. None of them measures energy transmission. A fiber can pass all three and still be delivering materially less than it did on its first case — and the study recorded total energy delivered as well, which leaves the gap in plain view. If what degrades a tip face is cumulative energy at the launch end, then a use count is a coarse proxy for it. Two departments can share a nominal count of 20 while one is dusting at low energy and the other is fragmenting at settings several times higher. Same count, different fiber.
The study’s headline saving was $64,125 for the reusable arm across those 541 procedures. Divide it out and that is about $119 per procedure — a real number, and a small one.
The reusable side has a floor that the count cannot go below
Write the reusable case out honestly and it has two terms, not one:
cost per use (reusable) = unit price / reuse count + reprocessing cost per cycle
Only the first term is divided. Cleaning, inspection, testing, packaging, sterilization and the labor around them are paid per cycle, whatever the count turns out to be. So as the reuse count grows, the price term collapses toward zero and the total converges on a floor set entirely by your reprocessing cost per cycle:
| Reuse count | Price term | Reprocessing | Cost per use |
| 3 | 33.33 | 25.00 | 58.33 |
| 10 | 10.00 | 25.00 | 35.00 |
| 29 | 3.45 | 25.00 | 28.45 |
| 100 | 1.00 | 25.00 | 26.00 |
At a count of 100 the price of the fiber has almost stopped mattering. The cost per case is the sterilizer and the technician, and it is essentially the same number at 50 uses as at 500.
That gives the comparison a decision test built from three numbers a purchaser already has:
If your reprocessing cost per cycle is higher than the single-use unit price — which already contains the sterilization and the pouch — no reuse count can save you. If it is lower, then the reusable case is worth building, and the count determines by how much.
Which is why the published literature argues with itself. The classic results run strongly toward reusable. A cost analysis of laparoscopic cholecystectomy put an all-disposable instrument set at roughly 19 times the per-procedure cost of reusable, and an earlier Belgian market study put the same comparison at 7.4 to 27.7 times. But note what those studies priced: the instrument set itself, with the 2005 analysis attributing the gap primarily to the purchase price of the disposables. Expensive forged steel, bought in disposable form, loses badly.
What each side is really paying for
Reusable. Labor per cycle, itemized: pre-treatment, transport, cleaning, disinfection, drying, inspection and function testing, packaging, sterilization, storage, and the log entry that ties the cycle to the device. Then the sterilization cycle itself, in a published range of roughly $33–80 for steam and $81–185 for low-temperature alternatives — and a fiber assembly’s polymer jacket and strain relief sit exactly in the category that pushes you toward the low-temperature end. Then consumables, then the scrap rate: fibers that fail your own inspection at cycle 6 and take their remaining unamortized life with them. Then the traceability your reprocessing quality system has to carry, and the annual external audit of that activity.
Single-use. Unit price, with sterilization, pouch, lot marking and shelf life already inside it. Waste disposal per unit, which is small for a fiber and not small for a full tray. Storage and carrying cost, which for a coiled bare fiber is also small — the 2019 study weighed the reusable side at 42 kg across three containers against 1.2 kg for the single-use equivalent, and a fiber sits at the good end of that ratio. What single-use does not buy you is capped exposure: a forecast that is wrong by 30% is wrong in the same direction on the cost line, while a reusable fleet absorbs a slow quarter by sitting idle.
The regulatory floor under the denominator
None of the arithmetic above is legal in every jurisdiction, and this is the part where the denominator stops being an engineering question.
Under Regulation (EU) 2017/745, reprocessing a single-use device may only take place where permitted by national law (Article 17). Anyone who reprocesses one for further use within the Union is considered the manufacturer of the reprocessed device and takes on the manufacturer’s obligations, including traceability. Member states may apply a lighter regime to reprocessing within a health institution, or by a third party acting on its behalf, but only on conditions — safety and performance equivalent to the original, and compliance with the common specifications in Commission Implementing Regulation (EU) 2020/1207, certified by a notified body.
The labeling consequences are concrete. A reprocessed device must carry the reprocessor’s identity, a statement that it is a reprocessed single-use device, the number of reprocessing cycles already performed and any limitations on the number of cycles, with the original manufacturer’s name moving off the label and into the instructions for use. The count is not a private assumption in that regime. It is a disclosure on the device.
The United States runs a different structure — nationally permitted rather than state-by-state, with the reprocessor registering, listing, assigning a UDI and labeling per Section 502(v) of the FD&C Act (“Reprocessed device for single use. Reprocessed by [name].”).
And the direction of travel is toward more evidence, not less. The Commission’s proposed amendments to the MDR’s Article 17 would require a manufacturer to justify a single-use indication in light of the device’s design, materials and properties, with that justification forming part of the technical documentation — and would require the IFU to set out the appropriate reprocessing process wherever a device is not intended for single use. In other words, “single-use” is on its way to becoming a claim that has to be supported rather than a sales habit.
Where the number is, and what to ask for
The reusable denominator is not something you deduce. It is in a document, and the document is required to say it. Annex I, Section 23.4(n) obliges the instructions for a reusable device to give the validated reprocessing process and the information identifying when the device should no longer be reused — signs of material degradation, or the maximum number of allowable reuses.
Three consequences, in order of how much trouble they save:
- If the number is not in the IFU, the fiber was not validated as reusable. That is not an opening position in a negotiation; it is the end of the analysis. No cost model you build will change what the device is.
- Ask for the count and the basis in the same breath. The count without its basis is the same unverifiable input whichever document it arrives on — the instructions themselves are the right place for it, and the fiber datasheets in our downloads library are the right place for the geometry that drives it.
- Ask what the count was counted against. A validated cycle count is a count of reprocessing cycles survived, not of delivered energy. Where a supplier can also tell you the energy basis behind the count — joules delivered, at what settings — you can compare it against your own case mix. Where the count is a number without a basis, treat it as a category label.
Commercial terms sit outside all of this — minimum quantities, lead times and tier pricing are a separate conversation — and our bare fiber range is where the two buying arrangements of one design sit side by side, so the arithmetic above can be run on your own volumes rather than ours.
The two procurement leads at the top of this page were not disagreeing about clinical practice, and neither needs to be told which fiber is safe to use — that question belongs to the IFU and the clinician holding it. One divided by 1. The other divided by a number that came from somewhere she did not have to look up.
That is the whole difference. The cheapest per-case number in any spreadsheet belongs to whoever filled in the denominator without reading it, and it will keep being the cheapest right up until someone asks for the source.
This article is about procurement, labeling and documentation. It is not legal advice, and it is not a clinical recommendation — where a device may be reprocessed, and whether a specific fiber should be used for a specific case, are governed by the instructions for use and by your own regulatory and clinical judgment.