Abstract:
Choice of implant for patients aged sixty-five years or younger
requiring hip arthroplasty is a topic of current debate. Those
in favor of resurfacing maintain it offers greater range of
motion and hence activity. In this study, we reviewed the Oxford
Hip Score’s (OHS) and Duke Activity Score’s of patients that had
undergone either total hip replacement (THR) using an Elite Plus
Stem, or hip resurfacing using a Birmingham Hip Resurfacing (BHR).
The THR cohort comprised 34 implants (4 bilateral), 17 men and
17 women, mean age 56.08 years. The resurfacing cohort comprised
27 implants (3 bilateral), 18 men and 9 women, mean age 50.51
years. The mean difference calculated between pre- and post-op
OHS was 25.33 and 22.08 for the THR and resurfacing cohorts
respectively. The mean Duke score was 42.3 and 53 for the
cohorts respectively.
Using the pre-operative and post-operative change in the Oxford
Hip Scores, no statistically significant difference was found
between the THR and resurfacing cohorts using a two-sided
Mann-Whitney U Test (p = 0.2891). There was a statistically
difference found between the THR and resurfacing cohorts with
regards to activity using post-operative Duke scores, (p =
0.0047).
This study has emphasized the use of hip scores. In terms of
reducing pain, both prostheses appear equally effective. With
regards to activity the resurfacing cohort faired better. Our
study suggests at one year post-op, younger patients with a
resurfacing have a greater activity level than those with a THR.
J.Orthopaedics 2009;6(4)e8
Keywords:
Total hip replacement; Total hip resurfacing; Activity; Duke
Activity Status Index
Introduction:
The choice of hip implant for young active patients is currently
controversial, with no clear concensus1. Survivorship
analysis varies for each prosthesis, 84% survival at 15 years
for young patients using an Exeter Universal/Exeter All-poly
prosthesis2, to 99.8% survival at 8 years using a
Birmingham Hip Resurfacing3. The debate regarding
survivorship will continue until comparative long-term results
are published. In addition to survivorship, it has been
highlighted that we must also consider activity levels in this
debate4. To date, few studies have directly examined
activity levels in younger patients undergoing total hip
arthroplasty versus resurfacing. With reference to patients’
aged 55 of less undergoing resurfacing, McMinn3
stated 97.6% of patients went on to lead “an active lifestyle”
following surgery. The proposed greater level of activity and
return to a normal lifestyle in patients whom undergo
resurfacing, is an argument that has gained weight with
clinicians in favor and those that market resurfacings5.
In this study we reviewed the pre- and postoperative hip scores
of patients aged sixty-five or less undergoing total hip
replacement (THR) or hip resurfacing.
Materials
and Methods:
All patients undergoing primary hip arthroplasty at our
institution were routinely asked to complete an Oxford Hip Score
(OHS) preoperatively and at subsequent follow-up to measure the
outcome of surgery6. The Oxford Hip Score is one of
the most widely accepted and commonly used scoring systems in
hip surgery. In addition to the OHS, we asked patients to
complete a pure activity score at one year, in the form of the
Duke Activity Status Index. Five of the twelve questions
comprising the OHS deal with pain and the remainder, activities
of daily living. All patients that had completed a pre-operative
and 1 year post-operative OHS were asked to complete the Duke
Activity Status Index (DASI). The DASI was developed in 1989 to
accurately measure functional capacity of patients undergoing
exercise testing by the Department of Medicine, Duke University
Medical Centre7 (Duke University Medical Centre,
Durham, North Carolina, 27710). The Duke Activity Status Index
consists of twelve short questions regarding levels of activity
(table 1). The maximum score is 58.2 and minimum score is 0.
Points are awarded depending on the difficulty level of the
activity; for example, running scores 8 points, walking 1.75.
Item
|
Score
|
1.
Can you take care of yourself (eating,
dressing, bathing, or using the toilet)? |
Yes – 2.75
No – 0 |
2.
Can you walk indoors, such as around your house?
|
Yes – 1.75
No – 0 |
3.
Can you walk a block or two on level ground? |
Yes – 2.75
No – 0 |
4.
Can you climb a flight of stairs or walk up a hill? |
Yes – 5.5
No – 0 |
5.
Can you run a short distance? |
Yes – 8
No – 0 |
6.
Can you do light work around the house, such as
dusting or light washing? |
Yes – 2.7
No – 0 |
7.
Can you do moderate work around the house such as
vacuuming, sweeping floors or carrying in groceries? |
Yes – 3.5
No – 0 |
8.
Can you do heavy work around the house, such as
scrubbing floors or lifting and moving heavy furniture? |
Yes – 8
No – 0 |
9.
Can you do yard work such as raking leaves, weeding
or pushing a power? |
Yes – 4.5
No – 0 |
10.
Can you have sexual relations? |
Yes – 5.25
No – 0 |
11.
Can you participate in moderate recreational
activities like golf, bowling, dancing, doubles tennis or
throwing a baseball or football? |
Yes – 6
No – 0 |
12.
Can you participate in strenuous sports such as
swimming, singles tennis, football, basketball or skiing? |
Yes – 7.5
No – 0 |
Total |
58.2 |
Table 1:
The
Duke Activity Status Index
Population & Sample
The clinical details of the patients comprising the THR &
resurfacing cohorts are given in table 2. Of the 182 patients in
the THR cohort group, sadly 4 (2%) patients had died since
surgery, 2 (1%) patients had been revised for deep infection and
3 (1.6%) patients had moved outside of the health authority. Of
the 90 patients in the BHR group, all patients were alive at the
time of study, but 2 (2%) patients were excluded for deep
infection, 2 (2%) patients had moved outside of the health
authority and 1 (1%) patient was revised due to aseptic
loosening. At the time of study, no patient from either group
had reported any episode of dislocation.
Both the OHS and DASI assign a numerical value to each question.
Values were combined and a total for each questionnaire was
calculated separately, and recorded. When reviewing the very
first returned questionnaires, it was apparent that controls
were needed regarding how totals were calculated. In particular,
question 10 of the DASI; “Can you have sexual relations?” Many
patients chose not to answer this question because they felt it
too personal; they were widowed or could not have intercourse
for another medical reason, e.g. impotence. Given the age of
patients involved in the study, it is not surprising that this
occurred. Additionally, some patients answered both ‘Yes and No’
to questions. This did not follow any apparent pattern and
occurred solely within the Duke responses. It was decided that
for these ambiguous answers a “worst case scenario” would be
assumed, and subsequently the scoring for that question was
marked as zero. This control ensured all totals were calculated
in the same manner. Though it occurred much less when
calculating the OHS totals, the same controls were applied.
|
Elite Plus |
BHR |
Total number of prosthesis implanted |
191 |
94 |
Total number of patients |
182 |
90 |
Bilateral arthroplasties (%) |
9 (5) |
4 (4) |
Gender (%) |
|
|
Male |
79 (43) |
70 (77) |
Female
|
103 (57) |
20 (23) |
Total Number of Pre-Op OHS’s completed (%) |
161 (88) |
68 (75) |
Total Number of Pre-Op OHS’s completed (%) |
49 (30) |
28 (41) |
Total Number of Duke Scores completed (%)
|
34 (69) |
27 (95) |
Total number of remaining patients |
34 |
27 |
Bilateral arthroplasties (%) |
4 (12) |
3 (11) |
Gender (%) |
|
|
Male |
17 (50) |
18 (66) |
Female
|
17 (50) |
9 ( 34) |
Mean age in years (range) |
56.08 (30 to 65) |
50.51 (30 to 65) |
Diagnosis (%) |
|
|
OA |
24 (71) |
26 (96) |
RA |
3 (8) |
- |
CDH |
3 (8) |
1 (4) |
AVN |
2 (6) |
- |
#NOF |
1 (3) |
- |
SUFE |
1 (3) |
- |
Table 2:
Clinical
details of the patients comprising THR & resurfacing cohorts.
Results :
In the resurfacing cohort, the mean age range in years was 50.51
(30 to 65) and comprised 18 men and 9 women. The pre-operative
Oxford Hip Score had a median value of 44 (27 to 48) and a mean
of 35.81; post-operatively a median value of 16 (12 to 36) and a
mean of 17.29; the difference between them both (pre-op minus
post-op) had a median value of 23 (12 to 42) and a mean of
25.33. The total DASI for the questionnaire had a median value
of 58.2 (32.2 to 58.2) and had a mean of 53.
In the THR, the mean age range in years was 56.08 (30 to 65) and
comprised 17 men and 17 women. The pre-operative Oxford Hip
Score had a median value of 44 (29 to 57) and a mean of 43.79;
post-operatively a median value of 18 (12 to 55) and a mean of
21.70; the difference between them both (pre-op minus post-op)
had a median value of 24.5 (2 to 27) and a mean of 22.08. The
total DASI for the questionnaire had a median value of 48.1
(5.45 to 58.2) and had a mean of 42.3.
Statistical Analysis
The Mann-Whitney U Test was used to analyse the data, chosen
because of the unequal number of patients in each cohort, and
because both comprised a small number of patients. Initially the
test was used to compare the pre-op resurfacing OHS results with
the pre-op THR OHS results, and the post-op resurfacing OHS
results with the post-op THR OHS results. This was to ensure
that there was no statistically significant relationship
present, which would suggest we were comparing different
cohorts. The results, using a two sided Mann-Whitney U Test were
0.3413 (95% CI –6 to 2) and 0.1606 (95% CI –6 to 1) for the
pre-op and post-op results respectively. As neither were shown
to be statistically significant at the 95% confidence interval,
then it was possible to assume that statistically, the cohorts
were not different, and were in fact similar. The Mann-Whitney U
Test was used again, to look for a statistically significant
relationship between the differences produced by subtracting the
pre-op OHS result from the post-op OHS result, in the
resurfacing and THR cohorts. The result using a two-sided test
of 0.2891 (95% CI –2 to 7), demonstrated that there was no
statistically significant difference between the two sets of
results. Finally, the Mann-Whitney U Test was used again to look
for a statistically significant relationship between the DASI
scores of the resurfacing and THR cohorts. The result using a
two-sided test of 0.0047 (95% CI 0 to 15.5), demonstrated that
there was a statistically significant difference between the two
sets of results.
Discussion :
Pollard et al8,
found that when comparing 51 hybrid THR’s at an average
follow-up of 80 months versus 53 BHR’s at an average follow-up
of 61 months, there was again no statistically significant
difference between mean OHS, but the BHR cohort had a
significantly greater level of activity using the University of
California at Los Angeles (UCLA) activity score9.
Amstutz et al10 also found a statistically
significant greater level of activity when comparing 100 Tharies
resurfacings with 100 Trapezoidal-28 THR’s.
This study has a number of limitations. Firstly this is a
retrospective review of the hip scores obtained over a number of
years. Patients selected to undergo a resurfacing procedure were
not prospectively randomised into a ‘resurfacing treatment arm’.
Therefore they underwent the procedure as they either requested
it themselves because they felt they were ‘personally active’,
or were perceived by the surgeon as being a good candidate. This
is evidenced by the mean pre-operative OHS of 35.81 in the
resurfacing cohort, versus 43.79 in the THR cohort. The DASI
score, which was introduced post-operatively, was not used
pre-operatively and therefore we cannot conclude if both cohorts
were well matched in terms of pre-operative activity. Whilst
this study has focused on patients below sixty-five, with a good
age range in each cohort, the resurfacing cohort were younger,
with a mean age of 50.51 years versus 56.08. The follow-up
period of one year is also much shorter than in similar papers.
From this review we can conclude that using the Duke Activity
Status Index as a measure of function, for those patients
undergoing a hip resurfacing, at one year had a greater level of
activity than those whom underwent THR. In this study there was
no statistically significant difference at one year post-op
found between either cohort using the OHS. This may be a
reflection of the questions utilised by the OHS, six of which
focus upon pain. Both prosthesis appear to be as effective in
reducing pain, as one would expect. Without the benefit of using
a pure activity score in addition to the OHS, one may
incorrectly conclude that this is also true of activity. The
additional use of a pure activity score cannot be over stressed.
This study has highlighted the use of hip scores in assessing
patients and in particular the use of a dedicated activity
score. The DASI score is quick to implement and complete. It
takes into account many of the everyday activities that patients
will perform. The results obtained through it use are in keeping
with the established literature. The DASI score could be used to
assess activity in further areas of orthopaedic research and
should be a consideration.
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