Hip and Knee Arthroplasty - Surface Hippy Guide to Hip Resurfacing
Hip and Knee Arthroplasty - Surface Hippy Guide to Hip Resurfacing
Hip and Knee Arthroplasty - Surface Hippy Guide to Hip Resurfacing
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number is greater than 100, in which case we<br />
extend the graph until the number at risk reaches<br />
100. This avoids uninformative, imprecise<br />
estimates at the right tails of the distribution<br />
where the number of primary prostheses at risk is<br />
low. However, analytical comparisons of<br />
prostheses survival using log-rank tests <strong>and</strong><br />
proportional hazards models are based on all<br />
available data (ref Pocock SJ, Clay<strong>to</strong>n TC, Altman<br />
DG. Survival plots of time <strong>to</strong> event outcomes in<br />
clinical trials: good practice <strong>and</strong> pitfalls, Lancet<br />
2002; 359: 1686-89).<br />
Confidence intervals for the Kaplan-Meier<br />
estimates are point-wise Greenwood estimates<br />
<strong>and</strong> their appearance should not be used <strong>to</strong> infer<br />
whether overall differences in survival between<br />
prosthesis types are significant. Rather, the logrank<br />
tests <strong>and</strong> hazard ratios reported with each<br />
curve should be used for this purpose.<br />
When we refer <strong>to</strong> the cumulative percent revision<br />
(CPR) at a certain time, for example five years,<br />
we mean the complement (in probability) of the<br />
Kaplan-Meier survivorship function at that time,<br />
multiplied by 100. The cumulative percent<br />
revision, generically a “cumulative failure rate”,<br />
also accounts for the right censoring due <strong>to</strong> death<br />
<strong>and</strong> the ‘closure’ of the database at the time of<br />
analysis.<br />
Acknowledgements<br />
The Registry could not function without the<br />
cooperation of a large number of organisations<br />
<strong>and</strong> individuals. The Registry acknowledges the<br />
continued cooperation <strong>and</strong> support provided by<br />
those undertaking the surgery <strong>and</strong> completing<br />
the data forms, in particular all orthopaedic<br />
surgeons, registrars <strong>and</strong> nursing staff. The<br />
Registry would also like <strong>to</strong> acknowledge the<br />
continued support of all hospitals both public <strong>and</strong><br />
private that undertake arthroplasty surgery<br />
nationally. The support provided by each of the<br />
hospitals through their nominated coordina<strong>to</strong>r(s)<br />
is appreciated. A list of participating hospitals<br />
<strong>and</strong> coordina<strong>to</strong>rs is included on the following<br />
pages.<br />
The Registry has also continued <strong>to</strong> receive<br />
support <strong>and</strong> invaluable assistance from the<br />
Federal Government, State <strong>and</strong> Terri<strong>to</strong>ry Health<br />
Departments <strong>and</strong> Orthopaedic Companies.<br />
Report Review Prior <strong>to</strong> Publication<br />
As previously mentioned, members of the<br />
<strong>Arthroplasty</strong> Society were invited <strong>to</strong> attend a two<br />
day workshop <strong>to</strong> review, comment <strong>and</strong> provide<br />
advice <strong>and</strong> feedback on all sections of the report.<br />
This report is the report finalised <strong>and</strong> approved at<br />
that meeting. Prior <strong>to</strong> publication the report was<br />
provided <strong>to</strong> the Board of the AOA for<br />
consideration <strong>and</strong> approval.<br />
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