Hip and Knee Arthroplasty - Surface Hippy Guide to Hip Resurfacing

increasing age. Those individuals aged less than
55 years at the time of surgery have a five year
cumulative percent revision of 17.0%. The
remaining three age groups, 55-64, 65-74 and 75
years and older have a five year cumulative
percent revision of 13.0%, 12.3% and 7.0%
respectively (Tables KP8 and KP9).
Males have over twice the risk of revision
compared to females, revisions per 100 observed
component years for males is 4.6 compared to
2.7 for females. The five year cumulative
percent revision for males is 21.3% and for
females is 11.7% (Tables KP10 and KP11).
There is considerable variation in outcome
depending on the type of prosthesis used. The
revisions per 100 observed component years for
all nine trochlear prostheses are provided in
Table KP6. Of the most commonly used
prostheses the RBK and Avon have the lowest
rate of revision (1.8 and 2.1 respectively) (Table
KP6). The RBK however has fewer procedures
and has not been followed up for as long as the
Avon. The prosthesis with the lowest five year
cumulative percent revision is the Avon (9.5%)
(Table KP7).
Patella/Trochlear Knee Replacement
with a higher than anticipated Revision
Rate
The LCS has been identified by the Registry as
having a higher than anticipated rate of revision
compared to all other patella/trochlear
procedures with 4.98 revisions per 100 observed
component years (Hazard Ratio adjusted for age
and sex (Adj HR)=2.05; 95% CI (1.26, 2.94)
p=0.001) (Table KP24). The LCS
patella/trochlear prosthesis has a five year
cumulative percent revision of 23.0% (Table
KP25 and Figure KP10).
Unicompartmental Knee Replacement
This year the Registry is reporting the analysis of
25,607 primary unicompartmental knee
replacements to the 31 st December 2007. Almost
all unicompartmental procedures have been
undertaken for osteoarthritis (98.8%).
Usage
Unicompartmental knee replacement continues to
decrease as a proportion of all primary knee
replacements. In 2007 unicompartmental
procedures accounted for 9.7% of all knee
procedures compared to 10.7% in 2006 and
14.6% in 2003 (Figure KG3). The total number
of primary unicompartmental knee replacements
performed in 2007 was 3,448, representing a
continual decline from 4,102 procedures
performed in 2003 (Table KP12).
Types of Prostheses Used
The Registry has recorded the use of 23 different
types of unicompartmental knee replacement
prostheses, 20 of which were used in 2007. This
is an increase from 18 different prostheses used
in 2006. The ten most commonly used
prostheses accounted for 88.7% of all
unicompartmental knee procedures in 2007. The
Oxford 3 prosthesis continues to be the most
frequently used, however as previously reported
its use continues to decline reducing from 33.3%
of all procedures in 2003 to 27.9% in 2007. The
ZUK unicompartmental knee prosthesis was first
used in 2005 and is now the second most used
prosthesis (12.9% of all procedures in 2007).
Apart from the Unix, which has increased slightly
in numbers from 2006, most other
unicompartmental prostheses have declined in
use (Table KP12 and Figure KP4).
Changes in use with Gender and Age
The continued decline in use of this procedure is
evident in both males and females and all age
groups (Tables KP13 and KP14).
Unicompartmental knee replacement is most
commonly undertaken in the 55-64 year age
group (34.5% in 2007) followed by the 65-74
years (30.5% in 2007). Over 20% of individuals
are 75 years and older and less than 15% are
less than 55 years of age at the time of surgery
(Table KP14).
Fixation
Most unicompartmental knee replacements
recorded by the Registry have both cemented
tibial and femoral components (89.7%). The
proportion of uncemented unicompartmental
knee replacements has slowly increased from
8.3% in 2003 to 13.4% in 2007. Hybrid fixation
(either the tibial or femoral component
cemented) has remained unchanged, accounting
for 0.9% of all unicompartmental knee
replacements (Table KP15 and Figure KP5).
Considerable state and territory variation
continues with 40.3% cementless fixation in
Victoria, an increase from 35.6% in 2006, and
predominantly cement fixation in Western
Australia (98.3%). South Australia continues to
be the only state where hybrid fixation is used to
any extent (5.2%) (Figure KP5).
Outcomes of Unicompartmental Knee
Replacement
At one year, the cumulative percent revision for
unicompartmental knee replacement is 2.3% and
at seven years is 12.1%. This is almost three
times the seven year cumulative percent revision
of primary total knee replacement (4.3%) (Table
KG5).
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