Benchmarking 288,584 knees named the implant systems that do not measure up

Design

retrospective registry cohort applying ISAR benchmarking standards; Level III

Population

288,584 primary TKAs for osteoarthritis, 2001-2024, 45 implant systems; mean age 68, 61% women

Primary outcome

all-cause revision, as cumulative percent revision against benchmark thresholds at 2, 5, 10 and 15 years

Effect

42 of 45 systems met the 2-year benchmark and 37 of 42 the 5-year; at 10 years 13 of 25 superior, 4 non-inferior, 8 no benchmark; at 15 years 6 of 12 superior

The International Society of Arthroplasty Registries set thresholds for acceptable revision-free survivorship, and this study applied them to a closed US healthcare system's joint registry: every primary total knee arthroplasty for osteoarthritis from 2001 to 2024, 288,584 knees by 605 surgeons at 68 facilities, with barcode-verified implant tracking and chart-validated revisions. Follow-up was 96%, 91%, 85% and 80% at two, five, ten and fifteen years. Systems with fewer than 250 knees were excluded, leaving 45.

At two years, 42 of 45 systems met the benchmark, covering 99% of implantations. At five years, 37 of 42. By ten years the picture spread out: of 25 systems assessed, 13 were superior, four non-inferior and eight met no benchmark at all - but those eight were used in only 3% of eligible knees, while superior systems accounted for 91%. At fifteen years, six of twelve were superior and five non-inferior. The systems that failed did so consistently when the analysis was split by age and by gender, which is the finding that makes this more than noise.

The reassuring headline - most contemporary systems perform acceptably - is the less useful half. The useful half is that a small number of systems underperformed reproducibly at long follow-up, and that a surgeon has no way of knowing which without registry data. India has no equivalent national arthroplasty registry, so implant choice here is driven by supplier, price and habit rather than by survivorship. The action that follows is to ask what long-term registry evidence exists for the system you are using, and to record what you implanted in a form that could be retrieved in fifteen years.

• Ask for published registry survivorship data at ten and fifteen years for the implant system you routinely use
• Record manufacturer, system name, component sizes and catalogue numbers in a retrievable form for every arthroplasty
• Treat two-year and five-year data as nearly uninformative for implant choice - almost everything passes
• Where a system has no long-term registry data at all, say so when consenting a younger patient
• Give the patient a copy of their implant details to keep

Why it matters

It shows that implant survivorship differences are real and detectable, and only visible to someone with registry data - which most surgeons here do not have.

Don't overread it

This is one US healthcare system's registry - the systems that passed or failed there may not be the ones in use elsewhere, and it is a retrospective cohort, not a comparison adjusted for patient risk.

The statistics, in plain English

The benchmarking rules are deliberately asymmetric: a system passes the early benchmark if the lower bound of its revision-rate confidence interval sits at or below the standard, but must have its upper bound at or below the threshold to be called superior at ten and fifteen years. That means early benchmarks are easy to clear and late ones are not, which is why 93% passed at two years and half were superior at fifteen. A system that failed was not necessarily bad - small numbers widen the interval and can push the upper bound over the line - but failing consistently across age and gender strata, as these did, is harder to explain that way.

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