Hip and Knee Arthroplasty - Surface Hippy Guide to Hip Resurfacing

(7.5%), pain (7.2%), lysis (6.9%) and patellofemoral
pain (5.6%) (Table KR5).
Analysis of First Revision of Known
Primary Knee Replacement
The essential difference between the known
primary procedures subgroup of revisions
compared to all revision procedures is that
because the primary has been recorded by the
Registry and the revision must have occurred
subsequent to this, these revisions are either
early or mid term revisions.
Type of Revision Knee Replacement
There are differences in the type of ‘revision in
the known primary’ group when compared to the
‘all revision’ group.
The ‘revision of known primary’ group has a lower
proportion of major revisions (63.1%) compared
to the ‘all revision’ group (67.5%). There is also
a reduction in the proportion of major revisions
that are major total revisions (62.5% compared
to 70.3%). Other differences include a higher
proportion of femoral only major revisions
(11.4% compared to 6.6%) and greater use of
unicompartmental knee components (5.4%
compared to 2.4%) (Table KR6). There is also a
higher proportion of minor revisions (37.0%
compared to 32.5%). The most common minor
revisions are insert only (43.1%) and patellar
resurfacing only (40.9%) (Table KR7).
Diagnosis
Diagnoses are similar between the ‘revision of
known primary’ and ‘all revision’ groups with the
exception of those diagnoses associated with
wear. Diagnoses associated with wear occur
more frequently in the ‘all revision’ group, with
the exception of loosening which occurs in a
similar proportion between the two groups. Pain
and patello-femoral pain occur more frequently in
the ‘revision of known primary’ group compared
to the ‘all revision’ group (Table KR5).
Outcome of Known Primary Revision
Knee Replacement
This analysis examines the risk of subsequent
revision following the first revision of known
primary unicompartmental and primary total knee
replacement. Primary unispacer, partial
resurfacing, patella/trochlear and bicompartmental
procedures have been excluded from this
analysis due to small numbers. First revisions
revised for infection have been excluded for the
same reasons as previously detailed in the
outcomes of the first revision of ‘known primary’
hip replacements.
The outcomes of the first revision of known
primary unicompartmental knee replacement
(1,532 procedures) and known primary total knee
replacement (3,122 procedures) are considered
separately.
Outcome of First Revision of Known
Primary Unicompartmental Knee
Replacement
The outcome of the first revision of primary
unicompartmental knees is dependent on the
type of first revision undertaken. There are four
options for revising a unicompartmental knee
replacement. The first three options are
unicompartmental to unicompartmental revisions,
minor revision (insert replacement), major partial
unicompartmental revision (replacement of either
the tibial or the femoral prosthesis) and major
total unicompartmental revision (replacement of
both femoral and tibial unicompartmental
prostheses). The final option is to convert the
unicompartmental knee to a total knee
replacement.
Revision to a total knee has a significantly lower
rate of re-revision compared to a
unicompartmental to unicompartmental option.
The outcome of the three different
unicompartmental to unicompartmental options
appear similar, however it is difficult to be certain
about the major total unicompartmental revision
group as only a few of these procedures have
been performed (Table KR8).
Unicompartmental to unicompartmental revisions
when combined into one group have a revision
rate of 9.3 revisions per 100 observed
compartment years compared to 3.0 for
unicompartmental to total knee. The rate of
revision of a unicompartmental to
unicompartmental revision is almost three times
greater than a unicompartmental to total knee
(hazard ratio (adjusted for age and sex) (Adj
HR)=2.97; 95% CI (2.14, 4.14) p