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Australian Orthopaedic Association -
National Joint Replacement Registry 2009 Annual Report
2009 ANNUAL REPORT
- View Full Report by Clicking Here
Highlights of report by Patricia Walter 10/2/09
This report is based on the analysis of
224,390 primary and revision hip replacements received by
the Registry with a procedure date up to and including 31st
December 2008. This is an additional 32,717 hip procedures
compared to the Annual Report released in 2008. In this category of hip replacement there are
147,422 conventional total hip replacements representing
92.3% of all hip replacements and 12,093 total
resurfacing hip replacements representing 7.6% of all hip
replacements.
Total resurfacing continues to decline
and in 2008 accounted for 6.1% of all primary total hip
replacement, a reduction from 8.8% in 2005.
The use of primary total resurfacing hip
replacement has declined for the third year in a row.
Analysis on a variety of factors affecting outcome has again
been presented. These include primary diagnosis, type of
prosthesis, gender and age. Patients having a total
resurfacing for osteoarthritis are revised less
frequently than patients with developmental dysplasia of the
hip. Females have a significantly higher rate of revision
compared to males and the risk of revision increases with
age. Males have an age related risk of revision which is
significantly higher after the age of 65 years.
As reported last year, the difference in
outcome related to gender is largely due to the size of the
femoral component. There is an inverse relationship
between risk of revision and size of the femoral head
component. Increased revision with increasing age and the
relationship to femoral component head size indicate that
both bone volume and quality are factors that may impact on
the outcome of this procedure.
As with primary conventional total hip
replacement outcome is also determined by the prosthesis
used. The ASR and Durom, reported last year as having a
higher than anticipated rate of revision, continue to
demonstrate more than twice the risk of revision compared to
other resurfacing prostheses. In addition, the Recap
resurfacing prosthesis has been identified this year as
having more than twice the rate of revision compared to
other resurfacing
prostheses. It is not uncommon for orthopaedic manufacturers
to attribute these differences to surgeon learning curve.
This approach however does not explain why most new
prostheses are not identified as having a higher than
anticipated rate of revision.
Primary Total Resurfacing Hip Replacement
The number of total resurfacing hip
procedures has continued to decline as a proportion of all
hip 47 procedures and also in terms of absolute numbers. The
BHR remains the most used prosthesis accounting for 50.9% of
all total resurfacings in 2008. The Mitch TRH was the second
most used prosthesis and showed a small increase in 2008.
The ASR and Durom showed a small decline in use and the
Cormet HAP BiCoat showed an increase in usage from 71 in
2007 to 84 in 2008. The ten most frequently used total
resurfacing prostheses accounted for 99.9% of all procedures
implanted in 2008.
Age And Gender
Age has a significant effect on the risk
of revision for primary total resurfacing and the risk of
revision increases with increasing age. At seven years the
cumulative percent revision for patients aged less than 55
years is 4.7%, 55-64 and 65-74 are both 5.6%. At seven years
females have more than twice the cumulative percent revision
than males, 8.7% compared to 3.8%. The effect of increasing
age on the risk of revision is evident for both males and
females.
Fixation
Almost all total resurfacing procedures
utilise hybrid fixation with a cemented femoral component
and cementless acetabular component. There has been an
increase in cementless total resurfacing procedures (i.e.
cementless femoral component) in 2008. No comparative
outcome data by fixation are presented. The principal
cementless femoral components are the Biomet, Cormet 2000
HAP and Cormet HAP BiCoat.
Femoral Component Head Size
As reported for the first time last year
there is a relationship between femoral component head size
and the risk of revision for total resurfacing hip
replacement. Further data confirms an inverse 49
relationship between the femoral component head size and the
risk of revision. At seven years patients
with a femoral head size component 44mm or less have over
four times the risk of revision of patients with a component
head size 55mm or more, with a five year cumulative percent
revision of 9.2% and 2.3% respectively (Adj HR=4.30; 95%CI
(2.21, 8.37) p<0.001)
The effect of femoral component head size
is evident in both males and females. Gender difference in
outcome for total resurfacing procedures is largely due to
differences in femoral head size. There is no significant
difference between gender in the risk of revision after
adjusting for femoral component head size. Males and females
with femoral component head size less than 50mm have a
similar cumulative percent revision at seven years (8.4% and
9.5% respectively) and males and females with head sizes
50mm or greater also have a similar five year cumulative
percent revision (2.3% and 2.0% respectively).
Devices with Higher than Expected
Revision Rate
The same three prostheses previously
identified by the Registry have again been identified as
having a higher than anticipated rate of revision. These are
the Cormet 2000 HAP which is no longer used and has a 9.5%
cumulative percent revision at five years. Both the ASR/ASR
and Durom/Durom are still used and have a five year
cumulative percent revision of 8.7% and 6.7% respectively.
Newly identified this year is the Recap/Recap, of which
there have been 137 implanted. The one year cumulative
percent revision is 5.0% and this combination has over two
and half times the risk of revision compared to all other
total resurfacing procedures (Adj HR=2.59; 95%CI(1.29,
5.22) p=0.007)
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