hta_ knee intro.qxp - Ministero della Salute

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6.1.3 Evidence synthesis
After the application of the inclusion criteria we extracted data and conducted appraisal of
methodological quality in duplicate. Data were extracted from all articles meeting inclusion criteria
using a standardised data extraction form used in our previously published HTA reports 23
(Appendix 7). Registry-based studies were extracted using a specific form (Appendix 8). We summarised
studies using an evidence table by knee system. Methodological appraisal was conducted
using a specific assessment tool developed by Agency for Healthcare Research and Quality
(AHRQ) 24 that includes a list of domains to evaluate the quality of single studies (Appendix 9).
6.2 Assessment of outcome: effectiveness of knee prostheses
6.2.1 Effectiveness and safety of knee prostheses: definitions
We considered the effectiveness of knee prostheses used in Italy as the survival of the knee
system used in the primary TKR at a minimum period of follow-up of 5 years. The survival rate
can be calculated by subtracting 100 from the revision rate. Safety is strictly related to effectiveness.
Revision is understood as the failure of the prosthesis due to a non-traumatic event. The definition
of failure in traditional survival statistics is “revision of one or more implant components or
removal of the whole prosthesis”. Although the indications for revision are known to be sensitive
to local conditions, the general consensus appears to favour revision as a blunt endpoint encompassing
the main dimensions of outcome. We recognise the magnitude of other indicators of outcome
(e.g. pain, range of motion) but implant revision is the only event that can be precisely identified
and registered.
In our analysis we did not consider the effectiveness of the revision procedure (ICD-9-CM
81.55).
6.2.2 Literature results
A total of 519 abstracts were identified in the literature. We excluded 433 citations by reading
title and abstract. After this stage we identified 86 potential relevant studies which were retrieved
for full text reading. We excluded 81 studies for various reasons after application of inclusion criteria.
The list of excluded studies and the reason of exclusion are in Appendix 10.
Finally 5 studies were considered for inclusion in our systematic review. We found no systematic
reviews, 1 prospective comparative cohort study 25 , 2 randomised controlled studies 26,27 , 1
prospective cohort study 28 and 1 registry based study 29 . The list of included studies is in Appendix
11. The evidence flow is in the following flow chart diagram (Figure 6.1).