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ORIGINAL ARTICLE
Recovery and Prediction of Physical Functioning Outcomes
During the First Year After Total Hip Arthroplasty
Kristi Elisabeth Heiberg, MSc,
a,b
Arne Ekeland, PhD,
c
Vigdis Bruun-Olsen, MSc,
b
Anne Marit Mengshoel, PhD
b
From the
a
Department of Physiotherapy, Bærum Hospital, Vestre Viken Hospital Trust, Sandvika;
b
Department of Health Sciences, Institute of
Health and Society, University of Oslo, Oslo; and
c
Martina Hansen’s Hospital, Sandvika, Norway.
Abstract
Objectives: To investigate recovery of physical functioning in patients during the first year after total hip arthroplasty (THA), and to predict
postoperative walking distance outcomes from preoperative measures.
Design: A longitudinal prospective design was used. Data were analyzed by repeated-measures analysis of variance and multivariate regression
analyses.
Setting: Two hospitals.
Participants: Patients with hip osteoarthritis were consecutively included and assessed preoperatively (nZ88), at 3 months (nZ88), and at
12 months (nZ64) after THA.
Interventions: Not applicable.
Main Outcome Measures: Physical functioning was assessed by objective measuresdthe 6-minute walk test (6MWT), stair climbing test, Index
of Muscle Function, figure-of-eight, and active hip range of motiondand the subjective measures by Harris Hip Score and Hip dysfunction and
Osteoarthritis Outcome Score.
Results: In objective measures, improvements were found from preoperatively to 3 months in 6MWT (P<.01) and stair climbing test (P<.05)
scores, while all measures had improved from 3 to 12 months (P.001). In contrast, all the subjective measures showed substantial
improvements at 3 months, but small further improvements from 3 to 12 months (P<.001). Age, sex, preoperative 6MWT distance, and hip
range of motion predicted 6MWT outcomes at 3 and 12 months (P.01).
Conclusions: The objective measures of physical functioning improved gradually during the first postoperative year, while the subjective
measures showed large early improvements, but little further improvements. Younger age, male sex, and better scores of walking distance and hip
flexibility before surgery predicted better score in walking distance at both 3 and 12 months after surgery.
Archives of Physical Medicine and Rehabilitation 2013;94:1352-9
ª2013 by the American Congress of Rehabilitation Medicine
Patients with hip osteoarthritis (OA) suffer from pain and disabil-
ities. When conservative treatment no longer is effective, total hip
arthroplasty (THA) is the treatment of choice. During the last couple
of decades, the evaluation of outcomes after THA has shifted from
focusing on success or failure of the implant to evaluate pain relief,
improvements in physical functioning, and quality of life.
1,2
A systematic review showed that patients with THA may exper-
ience considerable pain relief already a few days after surgery,
3,4
and
after 3 months pain intensity measures were reduced by approxi-
mately 60%.
5
Recovery of physical functioning has been evaluated
by objective measur es of performance, such a s walking distance,
6
and
by subjective measures, such as the Western Ontario and McMaster
Universities Osteoarthritis Index.
2,7
Compared with preoperative
scores, a deterioration in objective measures of walking distance
within the first postoperative weeks, small improvement at 3 months,
and further gradual increase to 12 months postoperatively have been
reported.
8-11
A different pattern has been revealed when the recovery
of physical functioning was assessed by subjective measures.
Approximately 50% improvement in Western Ontario and McMaster
Universities Osteoarthritis Index physical functioning score was
Supported by the South-Eastern Norway Regional Health Authority.
No commercial party having a direct financial interest in the results of the research supporting
this article has or will confer a benefit on the authors or on any organization with which the authors
are associated.
0003-9993/13/$36 - see front matter ª2013 by the American Congress of Rehabilitation Medicine
http://dx.doi.org/10.1016/j.apmr.2013.01.017
Archives of Physical Medicine and Rehabilitation
journal homepage: www.archives-pmr.org
Archives of Physical Medicine and Rehabilitation 2013;94:1352-9
reported from preoperatively to 3 months postoperatively,
5,10
with
further small improvements found at6 and 12 months.
5,11,12
Thus, the
pattern of recovery seems to be different depending on whether it is
evaluated by objective or subjective measures.
Studies examining the recovery of physical functioning after
THA have mostly applied either subjective or objective measures.
13
Two studies applied both subjective and objective measures to assess
the outcomes at least twice.
14,15
In these studies, most of the
improvementsin both objective measures and subjective measures of
physical functioning occurred within the first 3 months and only
small further improvements were found thereafter. These results are
in contrast to the aforementioned studies. Thus, it cannot be
concluded what to expect with regard to the course of recovery of
physical functioning.To address this issue further, our patient sample
was assessed by both subjective and objective measures of physical
functioning preoperatively and during the first year after THA.
For patients and health professionals to give realistic expec-
tations and set attainable therapeutic goals, it is important to know
whether the patients’ preoperative physical functioning is of any
significance to how their physical functioning will become post-
operatively. Prior studies have shown that advanced age, female
sex, multiple comorbidities, low patient expectations, high levels
of preoperative pain, and poor preoperative self-reported physical
functioning scores predict worse postoperative self-reported
physical functioning after THA.
16-20
Many patients desire to
improve their walking ability after surgery, and walking ability is
an important factor for living an active life and being independent
in daily activities.
21
We have, however, not found any studies
predicting the outcome in an objective measure of walking
distance after THA. Presently, we assumed that a patient’s walking
ability before surgery was related to the outcome in walking
ability after surgery. Furthermore, patients applying for THA have
often impaired hip flexibility and balance, which we think may
influence walking ability. We also presumed that patients who lead
a physically active life before surgery may achieve a good result
from surgery. Thus, these variables were entered as plausible
predictive factors in a regression model together with age, sex, and
preoperative pain severity.
The aims of this study of patients with THA were as follows:
first, to examine the changes in physical functioning assessed
before surgery and at 3 and 12 months after surgery by objective
and subjective measures, and second, to examine which preoper-
ative measures of physical functioning could predict walking
distance outcomes at 3 and 12 months after THA.
Methods
Study design, participants, and ethics
This article reports analysis of longitudinal data collected preopera-
tively and at 3 and 12 months after THA. The 12-month data were also
applied to evaluate the long-term effects of an exerciseprogra m.
22
This
exercise program showed a minor effect on walking after 1 year. Thus,
we have controlled for the exercise group in the statistical analysis.
Patients approved for primary THA were recruited from 2
hospitals in the Oslo area. They were enrolled from October 2008
to June 2010. Inclusion criteria were diagnosis of hip OA and
residence within a radius of approximately 30 kilometers to the
hospital, so that attending an exercise program after surgery could
be possible. The exclusion criteria were OA in a knee or contra-
lateral hip that restricted walking, as well as neurologic disease,
heart disease, dementia, drug abuse, or inadequate ability to read
and understand Norwegian. The study was approved by The
Regional Committee for Medical Research Ethics and the
Norwegian Social Science Data Services.
Patient characteristics
Before surgery, the patients completed a questionnaire including
items on age, sex, body height and weight, educational level,
marital status, and comorbidities.
Objective measures
6-minute walk test
The 6-minute walk test (6MWT) is a measure of walking ability. It
measures the distance in meters walked indoors at a comfortable
speed within 6 minutes.
23
The patients walked back and forth
along a 40-meter corridor. A clinically relevant improvement is
50 meters.
24
The 6MWT is considered to be an adequate measure
of physical functioning in subjects with OA and THA
11,25
and is
found to be reliable and valid.
26
Stair climbing test
The stair climbing test (SCT) also assesses walking ability. The
patients ascended and descended 8 steps, each 16 centimeters
high, as fast as they could without running. They used alternate
legs and were allowed to support themselves by holding onto the
stair rail. The time was measured in seconds.
Figure-of-eight test
The figure-of-eight test is a measure of balance. The patient walks
within a double set of circles. The outer circles are 180 centi-
meters in diameter, and the inner circles are 150 centimeters in
diameter. There is a 15-centimeter space between the lines in
which the feet must be placed during walking. Every step on and
outside the lines was registered, and the higher the number the
worse the score. The figure-of-eight test is reported to be reliable
and valid.
27
Index of Muscle Function
Index of Muscle Function (IMF) consists of tests of general
mobility, muscle strength, balance/coordination, and endurance.
The assessor evaluated the patient’s performance on a 3-point
scale (range, 0e2).
28
The total score ranges from 0 (best) to
40 (worst). The IMF is considered to be a valid and reliable
measurement tool for patients with OA.
28,29
Active hip range of motion
The degree of active hip range of motion (ROM) in flexion and
extension was measured by a goniometer,
30
summarized and
reported as the total score for active hip ROM.
List of abbreviations:
HOOS Hip dysfunction and Osteoarthritis Outcome Score
IMF Index of Muscle Function
OA osteoarthritis
ROM range of motion
SCT stair climbing test
THA total hip arthroplasty
6MWT 6-minute walk test
Recovery and prediction after total hip arthroplasty 1353
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Subjective measures
Harris Hip Score
The Harris Hip Score is a disease-specific measure of hip disabil-
ities. The topics included are pain, functions of daily living, and
gait.
31
The rating scale is from 0 (worst) to 100 points (best). The
Harris Hip Score is considered to have good validityand reliability.
32
Hip dysfunction and Osteoarthritis Outcome Score, version
LK 2.0
This disease-specific questionnaire consists of 5 subscales: pain,
other symptoms, activities of daily living, functions of sport and
recreation, and hip-related quality of life. The scores reach from
0 (worst) to 100 points (best). A change of more than 8 to 10
points in the Hip dysfunction and Osteoarthritis Outcome Score
(HOOS) is considered to be clinically relevant.
33
We translated the
Swedish HOOS 2.0 version into Norwegian using standard
procedures.
34
The Swedish questionnaire has been found to be
valid and responsive to changes.
35
Norway and Sweden are
culturally close. Therefore, the psychometric properties of the
Norwegian version were not tested.
Surgery and physiotherapy
Cemented hip prostheses by either Exeter
a
or Spectron
b
were used,
both with a posterolateral approach.
36
All the patients received
daily routine physiotherapy care while hospitalized,
37
and
69 patients (78%) continued with physiotherapy after discharge.
From 3 to 5 months postoperatively, approximately half of the
patients participated in an exercise program.
Statistical analysis
Descriptive data are presented as mean and its 95% confidence
interval or in number and percentage. The continuous data were
mainly normally distributed. The data analyses were conducted
with and without the outlier shown in figures 1 and 2, but the
outlier did not change our results. Changes in physical functioning
and symptoms over time were analyzed by repeated-measures
analysis of variance, with participation in an exercise program
(yes/no) included as a covariate. If Mauchley’s test of sphericity
was violated, we applied a Greenhouse-Geisser correction. Post
hoc tests were run with Bonferroni corrections.
The differences between men and women were analyzed by
independent sample ttests. The associations between the different
candidate predictors and between the predictors and the outcome
variables were analyzed by the Pearson’s correlation analysis.
Candidate predictors for the regression analysis were sex and the
variables that showed significant correlations (P.05) in the
bivariate analysis to the outcomes in the 6MWT at 3 and
12 months. When predicting the outcome in the 6MWT at 12
months, it was controlled for whether the patients had participated
in an exercise program or not.
38
If the correlation coefficient
between the independent variables was more than 0.7, they were
assumed to measure the same dimensions, and only the one with
the highest correlation coefficient with the dependent variable was
entered into the regression analysis.
39
The variables that fulfilled the correlation criteria were
included in the multiple regression analysis. The predictors with
the smallest contribution to explain the variance of the dependent
variable were excluded from the model by manual backward
stepwise procedure. Thereby, the best subsets of statistically
significant predictors were selected. For a final check of the
variables’ contribution within the model, the variables removed
from the models were individually re-entered. The scatter plots of
the distribution of the residuals for the models were acceptable.
The regression coefficients are reported with 95% confidence
interval. Pvalues of .05 or less were considered statisti-
cally significant.
Fig 1 Relation between the patients’ preoperative walking distance
in the 6MWT and change in walking distance from preoperatively to
3 months after THA (nZ88).
Fig 2 Relation between the patients’ preoperative walking distance
in the 6MWT and change in walking distance from preoperatively to
12 months after THA (nZ64).
1354 K.E. Heiberg et al
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Results
Patients
Before surgery 139 eligible patients were asked to participate.
Thirty-six patients declined, leaving 103 patients to be assessed
preoperatively. Fifteen patients withdrew from the study during
the first 3 months. They were mostly women and clinically worse
than those included in the study in preoperative measures of
6MWT, SCT, IMF, Harris Hip Score, and HOOS pain and activ-
ities of daily living (P<.05). Thus, 88 patients constitute the data
material preoperatively and at 3 months. Twenty-four patients
withdrew from the 12-month assessments. They did not differ at
preoperative- or 3-month assessments from the 64. At 12 months,
64 patients were left to be analyzed. The patient characteristics of
those participating in the study are presented in table 1.
Recovery of physical functioning
Recovery of physical functioning and symptoms from before
surgery and throughout the first year after surgery are presented in
table 2. The 6MWT distance improved by a mean of 9% and the
SCT score by 7% from preoperatively to 3 months postoperatively
(P<.05), and further improvements of 17% and 15% were found
from 3 to 12 months (P<.001). In the other objective measures, no
early improvement was shown at 3 months (P>.05), but from 3 to
12 months, figure-of-eight test score improved in mean by 30%,
IMF by 33%, and hip ROM by 12% (P.001). No statistically
significant difference in 6MWT outcome at 12 months was found
between those participating and those not participating in an
exercise program (P>.05) (fig 3). In the subjective measures, the
mean improvements in scores of physical functioning and symp-
toms varied from 49% to 127% from preoperative to 3 months
(P<.001). From 3 to 12 months, further improvements of 8% to
23% were found (P<.001).
The preoperative 6MWT was correlated with changes in the
6MWT at 3 months (rZ.59, P<.001) and with changes at
12 months (rZ.55, P<.001). Patients with low preoperative
6MWT score were likely to do better than preoperatively in the
6MWT at 3 months (see fig 1), while those with a high preoper-
ative 6MWT score needed a longer time to regain their score (see
figs 1 and 2). At 12 months, nearly all the patients had regained
and improved their preoperative 6MWT score. Those with low
preoperative scores achieved the largest gains (see fig 2).
Predictors of walking distance at 3 and 12 months
after THA
There were statistically significant differences between men and
women in preoperative scores of the 6MWT (PZ.05); SCT (PZ.01);
HOOS pain (PZ.04), activities of daily living (PZ.03), and sport
(PZ.03); and body mass index (PZ.04) and the 6MWT score at 3
(P<.001) and 12 months (PZ.04). The variables of patient charac-
teristics and preoperative measures of physical functioning, which
correlated statistically significantly with the 6MWT at 3 months, are
shown in table 3. The correlations showed almost a similar picture at
12 months (data not shown). Based on the correlation analyses, 5
predictive variables were included in the regression analyses.
Age, sex, preoperative 6MWT, and hip ROM were associated
with the outcome in the 6MWT at 3 and 12 months (P.01), and
in addition, the exercise program contributed at 12 months
(P<.001) (table 4). The total adjusted models explained 37% of
the variance at 3 months and 47% at 12 months (P<.001).
Discussion
The objective measures of physical functioning showed small but
gradual improvements during 12 months, while the subjective
measures of physical functioning had improved substantially at
3 months with small further improvements at 12 months. Age, sex,
preoperative walking distance, and hip flexibility explained 37%
of the variance in the 6MWT score at 3 months, and at 12 months,
the exercise program, age, sex, preoperative walking distance, and
hip flexibility explained 47% of the variance.
The present discrepancy in the recovery patterns evaluated by
objective and subjective measures is in accordance with some
previous studies,
6,8,12,40
but in contrast to 2 studies in which most
improvements in both objective and subjective measures occurred
during the first 3 months after surgery.
14,15
In these 2 studies, the
preoperative walking distance appeared to be shorter than for the
total sample in our study. We also found that the subgroup that had
the most limited walking distance preoperatively got the most
considerable gain at 3 months, while less improvement occurred
further on in the recovery course. Thus, it seems that the recovery
pattern in objective measures may differ depending on the
preoperative status of physical functioning. With respect to
subjective measures, there was an agreement across prior
studies
5,10
and our study that a large early improvement in
subjective measures can be expected after surgery. We agree with
prior authors that a plausible explanation can be that the
Table 1 Characteristics of patients with THA
Characteristics
Participants
Completing
Assessments
at 3mo (nZ88)
Participants
Completing
Assessments
at 12mo (nZ64)
Age (y), mean (95% CI) 66 (64e68) 65 (64e67)
Body mass index, mean
(95% CI)
27 (26e27) 27 (26e28)
Females 51 (58) 34 (52)
Educational level 12y 39 (44) 27 (42)
Educational level 13y 49 (56) 37 (58)
Married/cohabiting 61 (69) 50 (77)
Exeter prosthesis 66 (75) 47 (73)
Spectron prosthesis 22 (25) 17 (27)
Physiotherapy 0e3mo 69 (78) 46 (71)
Physiotherapy 3e5mo NA 32 (50)
Comorbidity
Heart attack 2 (2) 0 (0)
Angina 1 (1) 0 (0)
Diabetes 1 (1) 0 (0)
Cancer 4 (5) 3 (5)
Osteoporosis 4 (5) 2 (3)
Musculoskeletal disorders 10 (11) 9 (14)
Stomach/intestinal
problems
5 (6) 4 (6)
Lung disease 2 (2) 1 (2)
Psychological disorder 1 (1) 1 (2)
NOTE. Values are n (%) or as otherwise indicated.
Abbreviations: CI, confidence interval; NA, not applicable.
Recovery and prediction after total hip arthroplasty 1355
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substantial pain relief obtained in our study may have influenced
how the patients evaluated their physical functioning.
12
Moreover,
the high preoperative pain score and the pain relief at 3 months
may also explain the limitation in walking distance in a subgroup
of our patients before surgery and the early substantial improve-
ment in walking distance after surgery.
One question is whether the changes found in both objective
and subjective measures at 3 and 12 months are of any clinical
relevance. According to Perera et al,
24
the change in the 6MWT
score from preoperative to 3 months was considered to be a small
meaningful change, and the change from 3 to 12 months was
substantial. According to Roos and Lohmander,
33
the changes in
the subjective measures of HOOS from preoperative to 3 months
were considered as considerable meaningful changes, while the
changes from 3 to 12 months were of little clinical relevance.
However, the changes in both the objective and subjective
measures after 1 year compared with preoperative scores are of
substantial clinical relevance.
Presently, predictors of postoperative outcome in the 6MWT
were consistently identified among the preoperative objective
measures, while the subjective measures did not contribute in the
models. Better preoperative scores in the 6MWT and hip ROM
were associated with better postoperative scores in the 6MWT. We
have found only 1 recent study that is comparable to our study.
Nankaku et al
41
found that good scores on the objective measure
of ambulation, the timed “Up & Go” test, predicted the likelihood
of not using walking aids 6 months postoperatively. Thus, this
study and ours both suggest that patients’ preoperative physical
functioning matters for how the outcome is likely to become after
surgery. These results indicate that objective measures of physical
functioning can be useful in helping clinicians to set attainable
therapeutic goals. One can also speculate how exercises to
improve physical functioning may have an influence on outcome
in ambulation after surgery. Our model explained approximately
half of the variance in walking distance, and several other plau-
sible aspects, such as psychological and social aspects, may play
an additional role.
20
More research is needed to examine how
people’s physical functioning and other variables may predict the
postoperative outcome, and whether preoperative intervention
may have an influence on outcome after THA.
Study limitations
The internal validity of the study has to be discussed. In our
design, we have measured the outcomes only 3 times, and it is
likely that we may have overlooked an early postoperative decline,
but more importantly, a plateau of the improvements between 3
and 12 months, as reported by others.
6,42
With respect to the subjective measures, a ceiling effect may
have occurred because the patients tended to have early high
scores on subjective measures, leading to only limited possibilities
for a similar increase at 12 months. In these self-reports, several
questions address the ability to perform self-care activities, but
other subjective measures including more questions about the
Fig 3 Mean (95% CI) walking distance in the 6MWT preoperatively
(nZ64), at 3 months (nZ64), and at 12 months after THA in the
nonexercise group (black, nZ32) and the exercise group (white,
nZ32). Abbreviation: CI, confidence interval.
Table 2 Recovery of physical functioning in patients from before to 3 and 12mo after THA (nZ64)
Variables
Mean (95% CI) PValue for:
Before Surgery 3mo After Surgery 12mo After Surgery Overall Time Effect
Differences From
Before Surgery to 3mo
Differences
From 3 to 12mo
Objective measures
6MWT (m) 401 (377e425) 437 (416e458) 512 (490e534) <.001 .007 <.001*
SCT (s) 14 (13e16) 13 (12e13) 11 (10e12) <.001 .046 <.001
Fig. 8 (steps) 10 (6e14) 10 (6e13) 7 (4e10) .002 1.000 .001
IMF 13 (11e15) 12 (11e14) 8 (7e10) <.001 .722 <.001
Hip ROM () 81 (77e85) 84 (81e87) 94 (91e98) <.001 .068 <.001
Subjective measures
HHS 57 (53e61) 85 (82e87) 94 (92e96) <.001 <.001 <.001
HOOS symptoms 48 (45e52) 77 (75e80) 86 (83e89) <.001 <.001 <.001
HOOS pain 52 (48e55) 87 (84e90) 94 (92e96) <.001 <.001 <.001
HOOS ADL 56 (53e60) 84 (81e86) 92 (89e94) <.001 <.001 <.001
HOOS sport 35 (30e40) 64 (59e70) 79 (74e84) <.001 <.001 <.001
HOOS QOL 30 (26e34) 68 (64e73) 82 (78e86) <.001 <.001 <.001
Abbreviations: ADL, activities of daily living; CI, confidence interval; Fig. 8, figure-of-eight test; HHS, Harris Hip Score; QOL, quality of life.
* Significant interaction between the 6MWT at 12mo and the exercise variable (PZ.002).
1356 K.E. Heiberg et al
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patients’ ability to participate in more demanding leisure activities
may have depicted another recovery pattern.
One important issue to be discussed is how the participation
in a 6-week exercise program starting 3 months postoperatively
may have influenced our conclusions. In the statistical analysis,
we adjusted for the role of the exercise program. No statistically
significant differences between the exercise and nonexercise
groups were found at 12 months, and figure 3 illustrates that
the difference between groups was small. Therefore, it seems
unlikely that this has undermined the validity of our
conclusions.
Another important question is whether our results can be
generalized. The patients were asked to participate in a training
study, which may have given us a selected group that was healthier
and more motivated for physical activity than the general THA
population. They had few comorbidities and performed relatively
well on preoperative 6MWT when compared with patients in other
studies.
4,11
With respect to age, they were a few years younger than
Table 3 Bivariate correlation matrix between the 6MWT at 3mo postoperatively and the control variables and plausible preoperative
predictive variables in patients with THA (nZ88)
Variables 6MWT at 3mo 6MWT SCT Fig. 8 Hip ROM HOOS Pain HOOS ADL
HOOS
Sport HHS BMI
Age .22*.10 .08 .33
y
.17 .13 .09 .12 .03 .21
BMI .04 .24*.15 .06 .28
y
.15 .28
y
.18 .23*
HHS .24*.60
z
.47
z
.11 .21 .65
z
.67
z
.53
z
HOOS sport .33
y
.47
z
.37
z
.15 .16 .63
z
.72
z
HOOS ADL .29
y
.50
z
.33
y
.05 .18 .75
z
HOOS pain .15 .41
z
.30
y
.01 .25*
Hip ROM .23*.27
y
.11 .27*
Fig. 8 .27*.28
y
.14
SCT .42
z
.59
z
6MWT .47
z
Abbreviations: ADL, activities of daily living; BMI, body mass index; Fig. 8, figure-of-eight test; HHS, Harris Hip Score.
* Pearson’s correlation coefficient; P<.05.
y
Pearson’s correlation coefficient; P<.01.
z
Pearson’s correlation coefficient; P<.001.
Table 4 Preoperative predictors of walking distance outcomes in patients at 3mo (nZ88) and at 12mo (nZ64) after THA
Variables
Crude Estimates Adjusted Estimates
b95% CI Pb95% CI P
6MWT at 3mo
Age (y) 2.2 4.2 to 0.2 .030 2.5 4.3 to 0.6 .009
Sex (women [reference]/men) 61.5 30.4 to 92.5 <.001 65.3 34.8 to 95.9 <.001
Harris Hip Score 1.0 2.2 to 0.3 .119
Preoperative physical functioning variables
6MWT 0.2 0.0 to 0.4 .069 0.3 0.1 to 0.4 .002
SCT (s) 2.6 6.0 to 0.8 .126
Figure-of-eight test (steps) 0.6 1.8 to 0.7 .393
Active Hip ROM () 1.1 0.2 to 2.1 .017 1.2 0.3 to 2.1 .010
HOOS sport/recreation 0.6 0.2 to 1.4 .157
6MWT at 12mo
Age (y) 2.1 4.8 to 0.6 .118 3.1 5.5 to 0.8 .009
Sex (women [reference]/men) 60.5 21.4 to 99.5 .003 60.3 22.9 to 97.7 .002
Harris Hip Score 0.4 1.0 to 1.8 .582
Exercise (yes [reference]/no) 69.8 108.3 to 31.3 .001 70.3 104.8 to 35.8 <.001
Preoperative physical funtioning variables
6MWT 0.2 0.1 to 0.4 .189 0.3 0.1 to 0.5 .004
SCT (s) 2.3 6.3 to 1.6 .242
Figure-of-eight test (steps) 1.3 2.8 to 0.2 .089
Active Hip ROM () 1.5 0.2 to 2.9 .025 2.0 0.8 to 3.3 .002
HOOS sport/recreation 0.3 1.2 to 0.6 .534
NOTE. Unstandardized beta, 95% CI, and Pvalue given for crude and adjusted estimates in the multiple regression analyses. The total model explained
37% of the variance in the 6MWT at 3mo (adjusted R
2
Z.37) and 47% of the variance in the 6MWT at 12mo after surgery (adjusted R
2
Z.47).
Abbreviation: CI, confidence interval.
Recovery and prediction after total hip arthroplasty 1357
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the Norwegian THA population.
43
However, the patients included in
a review examining recovery seemed to cover almost the same age
span as our patients.
13
Thus, our study seems comparable to other
studies, and it may also reflect that hip arthroplasty is offered to
younger and healthier patients than previously described.
44
A high number of patients did not turn up for assessments,
which may have biased the results. At 3 months, those with the
worse preoperative pain and functioning withdrew, but those not
turning up for the 12-month assessments did not differ from the
others either at preoperative or 3-month scores. Anyway, we
believe that our patients represent a relatively healthy and physi-
cally fit sample and that these results can be generalized to
similar patients.
Conclusions
After THA, the patients’ objective measures of physical func-
tioning improved slowly throughout the first postoperative year,
while the subjective measures showed early substantial improve-
ments and only slight further improvements the following months.
Younger age, male sex, and better scores on walking distance and
hip flexibility before surgery predicted better score on walking
distance following THA.
Suppliers
a. Exeter Hip Unit, Princess Elizabeth Orthopaedic Hospital,
RD&E, Barrack Road, Exeter, EX2 5DW.
b. Smith & Nephew, Advanced Surgical Devices, 1450 Brooks
Rd, Memphis, TN 38116.
Keywords
Arthroplasty, replacement, hip; Recovery of function;
Rehabilitation; Walking
Corresponding author
Kristi Elisabeth Heiberg, MSc, Department of Health Sciences,
Institute of Health and Society, University of Oslo, P.O. Box 1089,
Blindern, N-0317 Oslo, Norway. E-mail address: k.e.heiberg@
medisin.uio.no.
Acknowledgments
We thank physiotherapist Mary Deighan Hansen, RPt, at Martina
Hansen’s Hospital and physiotherapist Anne Gunn Kallum, RPt,
at Bærum Hospital, Vestre Viken Hospital Trust, for all their
efforts in recruiting the patients, performing the measurements,
and collecting the data. We also thank the physiotherapy staff at
the hospitals for their participation.
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