Monday, August 8, 2011

Review of the 2009 Annual report from the National Joint Registry of Australia (part 3 of x)

In the last two posts, I reviewed the same report for the National Joint Registry of England and Wales. This one is quite a bit more detailed and contains more information on the Depuy hip ASR performance.  I was interested in this report to understand what was published in 2009 report, a report that was out over a year prior to the ASR recall.  I am also interested in the Pinnacle performance.

This report contains information on about 160,000 primary total hip replacements which account for 93% of all hip replacements reported by the registry.  This number contains all of the hip surgeries  reported up to and including 12/08 ( over 5 years I beleive).  This report provided substantial evidence to the market that there were serious problems with the Depuy ASR that resulted in its voluntary recall of the hip from the market.

1.  Metal on metal had the highest revision rate vs other bearing surfaces like poly, ceramic etc.

2.  When the head size is taken into consideration, and it is greater than 28, metal on metal has the highest risk of revision.  That rate is 4.4% with MoM and 1.7 with metal on poly. Ceramic on Ceramic had a 5 year revision rate of 2.7% and ceramic on poly had a revision rate of 2.1

3.  For each of the materials, larger head size means smaller revision rate than smaller head sizes.  That is not the case for MoM.  In fact, the opposite is the case.

4.  Something very interesting:  There are approximately 1385 combinations of cups, hips and stems that can be interchanged from different companies.  So the problem of monitoring efficacy with certain pieces can be daunting to some extent.  Once you interchange the materials and the manufacturers parts,  lots of variables are introduced  into any equation.  I had no idea of the vast amount of choices available to an orthopedic surgeon.  More on this later.  My guess is that most of these guys use few lines albeit, many surgeons abound so that leaves room for lots of options to say the least.

5.  Revision detail is interesting in this report.  There is a clear list of parts which have resulted in problems over time.  More later.

6.  There were 9 newly identified hip combinations identified in this report has having a higher than anticipated rate of revision.  Interesting that the exact devices causing problems are listed with the revision rates.  Seems as thought the issues are quite visable well in advance if the surgeons are reading these reports.

7.  The hazard ratio for  Depuy ASR is significantly higher than other hips from one month post surgery on.

8.  There were 3,971 Depuy ASRs reported to the registry
  • 126 revised
  • cumulative revision rate at 3 years post surgery was 5.4%
  • 50 of the revisions were acetabular revisions
  • 18 were a combination of femoral and acetabular
9. If you examine the yearly cumulative percent revisions of conventional hip replacement by materials with the primary diagnosis of Osteoarthritis not infection, the results look like this for year 8 (The ASRs are not included in this table. They are in a section by themselves which I will show tomorrow):

Metal on poly

They are all kind of in the same arena so it would be easy to identify outliers like the Depuy ASR!

More tomorrow on Pinnacle and the ASR tomorrow.  Both are hips manufactured by Depuy.  One seems to have done quite well (Pinnacle) while the other has of course not done well compared to its peers.

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