hta_ knee intro.qxp - Ministero della Salute

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The gross heterogeneity of reporting formats and attitudes coupled with the scarce evidence
from literature meant that we were faced with a sizeable loss of data both on costs and effects,
as we could not identify prostheses and assign costs and outcomes.
An additional problem is caused by the regulatory environment. In the current EU system prostheses
can enter the market in the absence of clinical trial data or even of comparative data. The
revised regulation at page 22 states that: “As a general rule, confirmation of conformity with the
requirements concerning the characteristics and performances referred to in Sections 1 and 2 of
Annex 1 under the normal conditions of use of the device and the evaluation of the side-effects
and of the acceptability of the benefit/risk ratio referred to in Section 5 of Annex 1, must be based
on clinical data”. Clinical data is defined as “the safety and/or performance information that is
generated from the use of a device. Clinical data are sourced from:
a) clinical investigation(s) of the device concerned, or
b) clinical investigation(s) or other studies reported in the scientific literature, of a similar
device for which equivalence to the device in question can be demonstrated, or
c) published and/or unpublished reports on other clinical experience of either the device in
question or a similar device for which equivalence to the device in question can be demonstrated.”
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With such vague guidance reliance on registers is the only possible solution. However no matter
how well-kept and collaborative the register may be, meaningful performance of knee prostheses
can only be judged after a number of years (ideally 10). By this time a new prosthesis often
considered “better” than the existing ones has entered the market and has begun to supersede
existing prostheses for which there is now better evidence. At this point the process has to start
all over again, limiting the decision-making usefulness of any register for new devices recently
introduced into a market.
Despite the limitations and constraints of our study we were able to show that purchase price
and effectiveness per se are not sufficient to inform decision makers. What is required is the linking
of the two into incremental cost-effectiveness ratios within prostheses design classes. It is
essential however that performance is calculated on recipient categories which are broadly similar
in terms of age, gender, indications and whenever possible, BMI.
According to our calculations the most cost-effective multiradius prosthesis in those aged 50
or more is NEXGEN LPS (Zimmer), whereas Scorpio (Styker) is the most cost-effective singleradius
prostheses. Our conclusions are insensitive to the inclusion of effectiveness data from RIPO or
AOAJRR. Little can be said for the remaining class which had only one prostheses per stratum, but
our ICERs provide at least some benchmarking for similar prostheses accruing sufficient survival
data in the future.
There are several limits to our analysis. The random sampling structure and relatively low
returns from our questionnaire meant that not all high throughput orthopaedic centres offering
TKR were sampled or responded. Whereas the former is a limitation of sampling which is obviated
by the sample’s representativness, this could have been undermined by the response rate
despite its good geographic spread. We personally solicited responses from all sampled centres
but we cannot be absolutely sure of the samples representativeness.