Abstract
Background: Valid outcome measurement tools are required to reliably
demonstrate the effectiveness and clinical outcomes of lower-extremity
arthroplasty. Having ascertained a lack of a practical and valid measure of
the change in actual daily physical activity that occurs prior to and
following lower-limb arthroplasty, we developed and validated a
lower-extremity activity scale.
Methods: The eighteen-level self-administered scale was developed
with the aid of content experts to ensure face validity. Validity and
reliability were assessed with the use of (1) pedometer measurements of
seventy subjects over seven days; (2) next-of-kin proxy measurements of the
activity levels of ninety patients before they underwent lower-limb
arthroplasty; and (3) application, and correlation with the Western Ontario
and McMaster Universities Osteoarthritis Index scores, in a prospective
seventeen-center clinical study of 297 consecutive patients undergoing
revision total knee arthroplasty. In this latter study, demographic and
comorbidity data were also collected. Univariate and bivariate correlations
were performed, and a multivariate structured equation modeling approach was
used to further test responsiveness, reliability, and validity of the
lower-extremity activity scale.
Results: Pedometer readings correlated with the activity levels
derived with the lower-extremity activity scale (r = 0.79). Of note was the
finding that age, weight, and body mass index did not correlate well with the
average number of steps per day (r = -0.32, -0.32, and -0.25, respectively). A
significant correlation was found between the lower-extremity activity scores
recorded by the patients and those reported by their next of kin (Pearson
correlation, r = 0.715; p = 0.0001) and between the initial lower-extremity
activity scores and two-week-retest scores (intraclass correlation = 0.9147; p
< 0.0001), demonstrating the validity and reliability of the scale. The
lower-extremity activity scale was responsive, accurately reflecting changes
in the patient's condition between baseline and the time of follow-up (p <
0.001), and it was reliable, with baseline values correlating with follow-up
scores (p < 0.001). The convergent validity of the lower-extremity activity
scale was established by correlations with the function scores (r = -0.301, p
< 0.001) and pain scores (r = -0.241, p < 0.001) derived with the
Western Ontario and McMaster Universities Osteoarthritis Index and with a
higher number of comorbidities (r = -0.244, p < 0.001). Multivariate path
modeling further demonstrated diminished activity in patients who had more
difficulty in functioning and a greater number of comorbidities.
Conclusions: We developed a lower-extremity activity scale and
validated that it was an effective instrument for the assessment of patients'
actual activity levels. It is easy to apply and interpret, and it is valid and
ready for use in the clinical setting. This scale will allow more accurate
analysis and prediction of outcomes. Consequently, it will become a useful,
practical adjunct to objective clinical decision-making and intervention for
patients undergoing arthroplasty.
The number of primary and revision total joint arthroplasties being
performed annually is increasing substantially. In 2002, 321,084 primary total
knee arthroplasties were performed, an increase of 5% compared with the number
performed in 2001, and 32,159 revision total knee arthroplasties were
performed, an increase of approximately
7.5%1. Despite these
increases, there is still a lack of definitive data on the precise
effectiveness and outcomes of these procedures. It is incumbent on the
orthopaedic community to provide such data in order to ensure proper patient
selection and reliably good and cost-effective clinical
results2,3.
To obtain these data, appropriate and valid measurement tools are required
to assess the various aspects of outcome. The tools that are currently
available for analysis of lower-limb arthroplasty focus largely on pain,
function, and satisfaction ratings. These are essential facets of outcome in
this population, but another, equally important aspect, which is overlooked in
these assessments, is the change in actual physical activity that typically
leads up to and follows lower-limb arthroplasty. Of the more than thirty
instruments that are available to assess physical activity, none fulfills all
of the criteria of being valid, reliable, and practical for this population of
patients with end-stage arthritis. Perhaps the scale with the greatest
relevance and usefulness for patients treated with arthroplasty is the
10-point investigator-rated University of California at Los Angeles (UCLA)
activity score. However, most activity instruments were developed for
individuals engaged in high-activity sports and typically assess maximum
activity at a single point in time rather than the actual activity
level4-9.
However, because successful reestablishment of satisfactory daily activity is
an essential component of clinical improvement following joint replacement,
validated instruments are needed to measure the actual activity of these
patients.
As well as being an important component of a patient's clinical outcome,
activity level has also been shown, although crudely, to correlate with wear
and potential failure of the
implant10-12.
A more accurate measure of actual activity would therefore be useful for
predicting implant survival and performance in patients with particular
activity levels13.
The objective of the current study was to develop a self-reported valid
measure of activity, which we call the Lower-Extremity Activity Scale
(LEAS).
As there is no gold standard for such an instrument, we developed a
protocol based on the principles of instrument development and validation
described by Ware and
Guyatt14. First,
the instrument was developed at the State University of New York at Buffalo by
one of the authors (K.A.K.) with the aid of content experts to ensure face
validity. Then we assessed validity in three ways: we derived data with
pedometers that subjects wore for seven days; we analyzed proxy measurements
made by next of kin; and, as pedometer readings are not absolute, we applied
the scale in a prospective multicenter clinical study of subjects treated with
total knee arthroplasty as part of the North American Knee Arthroplasty
Revision Study Group. The final step was done to determine the scale's
construct validity and to assess its discriminative reliability following
revision total knee arthroplasties by correlating its scores with those
derived with the Western Ontario and McMaster Universities (WOMAC)
Osteoarthritis
Index3,15-19.
The goal of the study was to develop a self-reported lower-extremity
activity scale that is reproducible (high signal-to-noise ratio) and valid
(measuring what it is intended to measure). Reproducibility was assessed with
discriminative (reliability) and evaluative (responsiveness) testing. Validity
was demonstrated by studying face and construct validation. Finally, the
instrument had to be easy to apply and interpret. The following sections
outline the development and testing of this new instrument.
Development of LEAS Questionnaire
The scale was developed to reflect the four major levels of lower-extremity
activity: (1) housebound (essentially unable to walk or a minimal ability to
walk), (2) more ordinary walking about the house, (3) walking about the
community, and (4) walking about the community as well as substantial work or
exercise. Twelve questions were formulated, with each of the last three
questions including three levels of response for finer gradation at the high
end of activity, without leading to any perceived overlap. This resulted in a
self-administered eighteen-level scale in which the patient chooses the
statement that best represents his or her self-perceived activity level
(Fig. 1). The final score is
simply the number of the chosen description. For example, a patient who is
entirely bedbound receives a score of 1 (minimum), and a currently competitive
athlete receives the maximum score of 18.
Reliability and Validity Testing of LEAS
The scale was tested for face validity on the basis of the expert opinions
of eighteen experienced arthroplasty surgeons. In this process, each point of
the scale was separately printed on its own card and the cards were placed in
a random order. The randomly ordered cards were then given to each of the
eighteen experts, who independently rearranged the cards in an ascending order
of activity according to their assessment. All of the surgeons exactly
reproduced the original order of the scale, with no recommendations to alter
the scale. This finding demonstrated face or content validity of the scale. It
also justified the use of this hierarchical (or Guttmann) type of scale, which
is straightforward and easy to administer. A respondent, by choosing the best
statement that describes his or her activity, implies that he or she can
perform all of the less intensive activities on the scale.
Construct Validation of LEAS: Proxy and Pedometer Measurements
The process of initial construct validation and scale reliability testing
involved two prospective studies, which were approved by our institutional
review board. In the first, a series of ninety patients seen prior to
operative treatment for osteoarthritis of the hip or knee completed the LEAS
questionnaire, after which relatives who lived with the patient and were
familiar with his or her activity level independently completed the
questionnaire for the patient. The second study involved measurements with a
pedometer worn for one week by a different group of seventy volunteers,
forty-five of whom were studied before or after a total knee or total hip
replacement (average age, 62.8 years) and twenty-five of whom were not
patients (average age, 41.7 years). Volunteers who were not patients were
included to ensure representation at the upper end of the activity scale, and
patients were analyzed before and after surgery in order to ensure that the
scale was responsive to change and was valid for patients at all relevant
time-points before and after joint arthroplasty. In addition, basic data on
these subjects (age, height, and weight) were recorded for analysis. The
pedometer readings were correlated with reported activities for the week and
with the scores on the LEAS that the patient had completed just prior to the
period of pedometer measurement.
Testing of Reliability of LEAS: Proxy Series
The reliability of the LEAS—that is, the extent to which the
instrument yielded the same results on independent repeated trials—was
then assessed by asking all ninety patients in the proxy series to complete
the scale a second time, two weeks following their first assessment.
Construct Validation of LEAS: Clinical Series
We then implemented the LEAS in a prospective seventeen-center cohort study
of patients treated with revision total knee arthroplasty. This step was
important in order to assess the scale's validity, reliability, and
responsiveness in a clinical setting involving changes in the patient status
between two time-points separated by six months and the revision procedure.
The specific inclusion and exclusion criteria for this study are listed in
Table I. There was no control
group in the study.
Following approval by our institutional review board and over a period of
twenty months, 297 consecutive subjects were enrolled in the study. Patient
assessments were performed preoperatively (baseline) and six months
postoperatively. Data were collected on patient demographics, comorbid
conditions (heart disease, high blood pressure, lung disease, diabetes, ulcer
or stomach disease, kidney disease, liver disease, anemia or other blood
disease, cancer, and back pain), reasons for the failure of the total knee
arthroplasty, the LEAS scores, and the WOMAC scores. The WOMAC Osteoarthritis
Index is a self-administered questionnaire that assesses osteoarthritis with a
series of twenty-four questions grouped into three subscales: degree of pain,
degree of difficulty in functioning, and degree of stiffness. Responses to the
questions are marked on a 5-point scale, with 1 point indicating the best
function and 5 points, the worst.
The frequency distributions and mean values were examined with univariate
analysis, with testing for floor and ceiling effects. The LEAS was correlated
with the three components of the WOMAC Osteoarthritis Index and with the
number of comorbidities. It was hypothesized that the LEAS would correlate
with all three WOMAC-based measures of osteoarthritis. It was also expected
that a higher number of comorbidities would correspond to a lower LEAS score.
Although a potential weakness of the analysis was that the list of comorbid
conditions had not been assembled as part of a validated instrument, such as
the Charlson comorbidity index, it was applied as a construct or proxy of the
overall health of the patients.
In hypothesizing the multivariate relationships among the components of the
WOMAC, the number of comorbidities, and the LEAS, we expected to find that the
WOMAC scores for difficulty in functioning (arthritis-related difficulty) and
the number of comorbidities (systemic difficulty) would be good predictors of
the LEAS score. In this logical model, pain and stiffness were hypothesized to
act as precursors of arthritis-related difficulty, as opposed to affecting the
LEAS directly. The corresponding path model contained five different error
terms, with two of them expected to correlate with one another. This model was
identified with use of the structural equation modeling approach (Amos
software, version 4.0; SPSS, Chicago,
Illinois)20.
Reliability and Responsiveness of LEAS: Clinical Series
The lower boundary of the test-retest reliability of the LEAS in this study
was estimated by correlating baseline values with follow-up scores, and
responsiveness was assessed by determining whether the LEAS could detect
change in patient status between the baseline and follow-up evaluations.
Validation of LEAS
The scores recorded in the first series of ninety subjects ranged from 2 to
15, with no appreciable floor or ceiling effects (i.e., most of the observed
values were not equal to or clustered next to the lowest or highest possible
value). The proxy test of construct validity demonstrated nearly identical
scores recorded by the patients (mean, 13.56) and their relatives (mean,
13.84), with good correlation demonstrated by the Pearson method (r = 0.715; p
= 0.0001).
In the pedometer-based test of construct validity, there was clear
correlation between the activity levels assessed with the LEAS and the
pedometer readings (r = 0.79). Of note, age, weight, and body mass index did
not correlate well with the average number of steps per day (r = -0.32, -0.32,
and -0.25, respectively).
Reliability of LEAS
The reliability of the scale was assessed by repeat testing of the first
proxy group of patients at two weeks following their first test. Significant
correlation was demonstrated between the test and retest performances
(intraclass correlation = 0.9147; p < 0.0001), demonstrating reliability of
the scale.
Clinical Validation of LEAS
The response rate was 96% (285 of 297) in the study of the patients treated
with revision total knee arthroplasty. The mean age of the study population
was 68.6 years (range, thirty-four to eighty-five years), and the
male-to-female ratio was 1:1.1. The mean body mass index was 31.8, with 154
subjects (54%) having a body mass index of >30, and the mean weight was
200.0 lb (90.7 kg) (range, 107 to 350 lb [48.5 to 158.8 kg]). Three-quarters
of the patients had four comorbidities or fewer. The most frequently reported
comorbidities were high blood pressure (62.1% of the patients) and back pain
(48.8%). The predominant modes of failure of the primary arthroplasty, which
were similar to those in other studies, included instability (eighty-two
patients; 28.8%), tibial osteolysis (seventy-eight; 27.4%), polyethylene wear
(seventy; 24.5%), femoral osteolysis (sixty-four; 22.5%), and tibial loosening
(sixty-three; 22.1%).
The frequency distributions of the baseline and six-month LEAS scores are
shown in the Appendix. The scores were spread over the range of the eighteen
possible activity levels (range, 2 to 16 for the baseline scores and 3 to 17
for the six-month scores). Histograms further demonstrated a close-to-normal
distribution of LEAS values at baseline
(Fig. 2) and the time of
follow-up (Fig. 3) as well as
the absence of any floor or ceiling effects.
Baseline LEAS scores were significantly correlated with the function and
pain scores of the WOMAC and with the number of comorbidities. All three of
these relationships were negative, as expected, in that a lower level of
activity was correlated with a higher level of pain (r = -0.241, p <
0.001), greater difficulty in functioning (r = -0.301, p < 0.001), and a
higher number of comorbidities (r = -0.244, p < 0.001). These results thus
confirmed convergent validity according to our hypothesized relationships
among these components, a finding that was sustained at the six-month
follow-up evaluation (Table
II). In contrast, although the degree of stiffness was
significantly correlated with the LEAS score at the time of follow-up (r =
-0.215, p < 0.01), this correlation was not significant at baseline. This
finding signaled that our logical model based on bivariate correlations
oversimplified the relationships between the measured variables and therefore
necessitated enhancement with multivariate models.
Multivariate path modeling was thus implemented with use of a structured
equation modeling
approach20. The a
priori model included two regression equations and five error terms. Two of
them (pain and stiffness) were expected to correlate with one another. One
regression equation reflected the direct impact of the WOMAC pain and
stiffness components on the WOMAC difficulty-in-functioning component. The
other regression equation formalized the dependency of the LEAS on the amount
of systemic health problems (i.e., the number of comorbidities) and
arthritis-related health problems (the WOMAC difficulty-in-functioning score).
The results are presented in Table
III. From the viewpoint of all general goodness-of-fit tests, this
single model better fit the data collected at the time of follow-up (higher p
value, lower chi-square normalized by degrees of freedom, and lower root mean
square error of approximation) than the data collected at baseline. This means
that this model better reflects the relationships observed at the time of
follow-up than those observed at baseline. Therefore, the baseline
relationships are more complex and likely to involve more variables.
Despite the lower descriptive accuracy at baseline, the models for baseline
and follow-up values nonetheless looked very similar. The worst WOMAC
difficulty-in-functioning scores were assigned to patients with more reported
pain and stiffness, with a clear dominance of the former (standardized
regression weights, 0.63 [relationship between pain and difficulty in
functioning] compared with 0.19 [relationship between stiffness and difficulty
in functioning] at baseline and 0.76 compared with 0.08 at the time of
follow-up). Limitations of physical activity were more often recorded by
patients with more arthritis-related difficulty in functioning and a greater
number of comorbid conditions. These latter two precursors of limited physical
activity have approximately equal weights, with slight preeminence of
arthritis-related difficulty in functioning. The critical ratio presented in
Table III has close to normal
distribution and thus allows estimation of the significance of the separate
effects. The threshold value (p = 0.05) of the critical ratio is 1.96, with
higher values corresponding to increased degrees of significance. The only
weight in Table III that does
not differ significantly from zero is "stiffness to difficulty" at
the time of follow-up. All other weights have associated significances of
better than 0.01, thus indicating that the models are stable.
Finally, convergent and divergent validity was tested with use of the
change in the LEAS scores between the baseline and six-month time-points.
Bivariate correlations were performed for the change in the LEAS scores as it
correlated with the change in the WOMAC component scores. Convergent validity
was sustained by the correlation between the change in the LEAS scores and the
change in the WOMAC pain scores (-0.291) and difficulty-in-functioning scores
(-0.300) (p < 0.001). The change in the stiffness scores, however, was not
significantly correlated with the change in the LEAS scores (-0.18; p =
0.814).
Clinical Responsiveness of LEAS
In addition to the validation tests of the LEAS performed separately at
each time-point (baseline and follow-up), analysis was done to examine the
responsiveness of the LEAS to changes in patient status. The significantly
lower mean WOMAC component scores at the time of follow-up are indicative of
an improvement in patient status (Table
II). These were mirrored by the LEAS scores, which were
significantly higher at the time of follow-up than they were at baseline (an
average increase of 1.07 ± 0.24, from 7.5 at baseline to 8.5 at the
time of follow-up; p < 0.001). This indicates that the LEAS is responsive
with regard to measuring relative improvement in patient status following
intervention.
Although total hip and knee arthroplasties have been associated with
almost unparalleled success, the specific patient-related factors that
determine that success remain relatively unknown. However, a full
understanding of these factors is necessary in order to ensure that the best
possible outcomes are achieved. Only through well-constructed and executed
studies in which the most accurate measurement tools are utilized will this
information be obtained. In the current study, we described and validated a
reliable tool for the assessment of activity—an essential outcome
measure—of patients treated with lower-limb arthroplasty. The scale was
rigorously tested in series of patients treated with total knee arthroplasty
because of end-stage arthritis, and the accuracy and applicability were found
to be uniformly satisfactory. The fundamental importance of this scale lies in
its practical measurement of actual patient activity, as opposed to the
often-measured isolated ability to perform a certain function.
The LEAS is self-administered. The fact that there were very few missing
responses in this cohort of patients indicates that the scale is easy to
comprehend, simple to complete, and therefore practical. Patients treated with
arthroplasty have been shown to be reliable in their use of self-administered
questionnaires, and such instruments do not alter the subjects' activity or
produce major selection
bias9. More
specifically, questionnaires that include statements about frequency,
duration, and/or intensity of leisure and work-related activities seem to
increase the reliability of these
instruments9,21-34.
The current study supports the findings of others that self-administered
questionnaires are practical, reliable, and inexpensive to administer and that
they save time and effort on the part of investigators, and these findings
reinforce our choice of the hierarchical design of the
scale9,24,26.
Aside from ease of use, self-administration has other attractive features.
As clinical practice and research continue to place increasing emphasis on
patient perspectives, it will be important to utilize outcome evaluation tools
that are completed by patients themselves. Surgeons have previously largely
determined whether a surgical procedure is successful on the basis of such
outcomes as radiographic findings and objective measurements. Although such
measures will continue to be important, patients' perceptions are now
increasingly recognized as being essential to comprehensive postoperative
evaluations35-39.
Activity is a critical aspect of the outcome of joint arthroplasty, with a
return to previous activity levels being a very important component of outcome
for most
patients4,40,41.
The results of our multicenter study demonstrate clearly that levels of actual
activity are significantly increased at six months following revision total
knee arthroplasty. The availability of a valid scoring system to evaluate
patient activity greatly enhances our ability to accurately assess both the
patients and the effectiveness of our interventions for them. Another reason
why an accurate instrument for evaluating patient activity following
arthroplasty is important is that activity has been shown to correlate with
implant
wear11,12
and therefore may influence the longevity of given implants used for either
primary or revision
arthroplasty5,13.
A previous notable study of activity assessment with the UCLA scale in a group
of patients treated with arthroplasty demonstrated correlation between
pedometer readings and the activity rating, but the average number of steps
per day taken by patients with the same UCLA score ranged very
widely4. One of the
next phases in the development of the LEAS will thus involve assessing the
correlation of each level of the scale with a specific number of gait cycles
per year or per day. This endeavor assumes greater importance in the light of
claims that activity will ultimately supplant more traditional, but indirect,
risk factors for wear and decreased implant survival, such as age, body mass
index, and
gender5,6,13.
In this regard, it is also important to note that our results support previous
findings that age, gender, and weight cannot be used as surrogates for
activity level because of the degree of
variability6,13,42.
Furthermore, body mass index did not correlate with patient activity, a
finding that differs from those in some
studies43,44.
A notable related finding in our study was that the mean body mass index
was in the obesity range, raising concerns regarding the generalizability of
our results. Although there was no control group or prospective analysis of
patients treated with primary total knee arthroplasty in the current study, we
nonetheless believe that several factors suggest that our findings are both
relevant and generalizable. First, we performed a large multicenter study that
included seventeen geographically dispersed centers. Second, it has recently
been demonstrated that a large proportion (37%) of patients treated with
primary total knee arthroplasty are
obese1. Finally,
recent
studies45,46
have demonstrated the survival of primary total knee prostheses to be lower in
obese people, and in morbidly obese people in particular. In view of all of
these findings, we think that obese subjects should, in general, be expected
to be more highly represented in a population of patients treated with
revision total knee arthroplasty and that our study can therefore be
considered representative pending more exacting analysis of this interesting
aspect of revision total knee
arthroplasty1,45,46.
In the series of revision total knee arthroplasties in this study, the
number of comorbidities at the time of follow-up correlated negatively with
the LEAS score and was predictive of poor function at the time of follow-up.
These findings show that the LEAS score and the number of comorbidities are
important predictors of outcome following surgery. The interaction of the LEAS
with comorbidities demonstrates that global factors have an impact on the
results of more specific instruments, suggesting that use of both global and
disease or system-specific tools is indicated in the analysis of outcomes of
revision total knee arthroplasty.
It should be noted that while the mean improvement in the LEAS score of
1.07 may seem small, it was found to be highly significant (p < 0.001).
Also, the 1-point difference (from 7.5 at baseline to 8.5 at the time of
follow-up) had a confidence interval that did not include zero, which further
indicates the significant improvement in activity level in this cohort of
patients treated with revision arthroplasty. Clinically speaking, this
difference represents a transition from mostly household walking to community
walking, which is a very relevant gain in activity. Finally, the LEAS is a
measure of actual activity of patients, and it collectively measures various
psychosocial factors that affect activity instead of simply evaluating the
status of the knee after revision. For example, if an individual were
generally sedentary in nature or occupation, his or her activity level would
not necessarily be expected to increase greatly after a revision procedure.
Thus, the improvement found in this study is meaningful for this
population.
The minor bimodal distribution of responses that was seen during the
clinical validation of the scale raises an important point for discussion.
This element of the scale can be explained in two ways. The first reason for
the bimodal distribution may be that the population presenting for revision
total knee arthroplasty is a nonuniform group with regard to their activity
levels. This could be related to the reasons for and the severity of the
prosthetic failure (for example, the degree of instability or bone loss) in
this cohort. An alternative explanation is that the middle of the scale
requires minor refinement to further categorize activity levels. Given the
comprehensive nature of the validation of the scale under a range of different
circumstances and through comparison with various parameters, it seems very
likely that the scale does not need to be adjusted. At most, the existing
levels within the scale may be need to be refined. With use of the scale in
the various relevant arthroplasty populations, we will be able to amass
normative data for the LEAS and this information will ultimately allow
specific comparisons between patient populations and treatment modalities.
Given the pedometer and proxy-based validations as well as the ongoing
practical clinical application of the scale, it has become apparent that the
LEAS represents a substantial advance compared with other scales for this
patient population. The instrument is clinically sound and easy to interpret,
in contrast to the WOMAC and Short Form-36, which are not readily applicable
in the day-to-day clinical care of
patients47. Having
been specifically developed and validated for arthritic patients, the LEAS
contrasts with commonly used scales that have not been validated or that were
developed for a sports-medicine or high-end-activity population. We envisage
immediate application of the LEAS in clinical and scientific protocols,
particularly in view of its relative simplicity and ease of use. For example,
given the results in the present study, the LEAS can be used in place of more
involved pedometer-based activity assessment and can supplant the use of other
activity scales in this population.
In conclusion, the LEAS is a reliable and effective instrument for the
assessment of the actual activity levels of a wide range of individuals. It is
easy to use, and our findings indicate that it will allow more accurate
analysis and prediction of outcomes of lower-limb arthroplasty. The LEAS will
also facilitate planning of effective interventions for the appropriate
patients at the right time and in the most cost-effective and
patient-beneficial manner possible.
Tables showing the frequency distributions of the LEAS scores at baseline
and at six months postoperatively are available with the electronic versions
of this article, on our web site at
(go to
the article citation and click on "Supplementary Material") and on
our quarterly CD-ROM (call our subscription department, at 781-449-9780, to
order the CD-ROM).
Note: The authors thank the North American Arthroplasty Revision
Study Group. Principal Investigator: Khaled J. Saleh, MD, University of
Virginia, Charlottesville, VA. Co-Principal Investigators: B. Bershadsky PhD,
University of Minnesota, Minneapolis, MN; C. Clark, MD, University of Iowa,
Iowa City, IA; E. Cheng, MD, University of Minnesota, Minneapolis, MN; G.
Engh, MD, Anderson Orthopaedic Research Institute, Alexandria, VA; T. Gioe,
MD, Veteran Affairs Medical Center, Minneapolis, MN; D. Heck, MD, Indiana
University, Indianapolis, IN; D. Hungerford, MD, Johns Hopkins
Medicine-Baltimore, MD; R. Iorio, MD, Lahey Clinic, Burlington, MA; K.
Krackow, MD, Buffalo General Hospital Kaleida Health, Buffalo, NY; R. Kyle,
MD, Hennepin County Medical Center, Minneapolis, MN; P. Lotke, MD, University
of Pennsylvania, Philadelphia, PA; W. Macaulay, MD, Columbia University, New
York, NY; S. MacDonald, MD, London Health Sciences Centre, London, ON, Canada;
M. Mont, MD, Sinai Hospital, Baltimore, MD; K. Mulhall, MD, University of
Virginia, Charlottesville, VA; J. Parvizi, MD, Rothman Institute Orthopaedics,
Philadelphia, PA; S. Scully, MD, Mayo Clinic, Rochester, MN; G. Scuderi, MD,
Insall, Scott, Kelly Institute, New York, NY; and R. Windsor, MD, The Hospital
for Special Surgery, New York, NY. Investigators: M. Bostrom, MD, The Hospital
for Special Surgery, New York, NY; R. Bourne, MD, London Health Sciences
Centre, London, ON, Canada; H. Clark;, MD, Insall, Scott, Kelly Institute, New
York, NY; L. Fink, RN, University of Iowa, Iowa City, IA; H. Ghomrawi, MPH,
University of Minnesota, Minneapolis, MN; S. Haas, MD, The Hospital for
Special Surgery, New York, NY; W. Healy, MD, Lahey Clinic, Burlington, MA; K.
Hepburn, PhD, University of Minnesota, Minneapolis, MN; R. Kane, MD,
University of Minnesota, Minneapolis, MN; P. Khanuja, MD, Johns Hopkins
Medicine-Baltimore, MD; R. Laskin, MD, The Hospital for Special Surgery, New
York, NY; J. McAuley, MD, Anderson Orthopaedic Research Institute, Alexandria,
VA; C. Nelson, MD, University of Pennsylvania, Philadelphia, PA; M. Phillips,
MD, Buffalo General Hospital Kaleida Health, Buffalo, NY; J. Purtill, MD,
Rothman Institute Orthopaedics, Philadelphia, PA; C. Rorabeck, MD, London
Health Sciences Centre, London, ON, Canada; E. Santos, MD, University of
Minnesota, Minneapolis, MN; T. Sculco, MD, The Hospital for Special Surgery,
New York, NY; J. Swafford, RN, University of Iowa, Iowa City, IA; and M.
Swiontkowski, MD, University of Minnesota, Minneapolis, MN.
Kane RS, Saleh KJ, Wilt TJ, Bershadsky
B, Cross WW 3rd, MacDonald RM, Rutks I. Total knee replacement.
Evidence Report/Technology Assessment No. 86 Rockville, MD: Agency for
Healthcare Research and Quality; 2003.
2003
Ritter MA, Albohm MJ, Keating EM, Faris
PM, Meding JB. Comparative outcomes of total joint arthroplasty. J
Arthroplasty.1995;10:
737-41.10737
1995
[PubMed][CrossRef]
Kreibich DN, Vaz M, Bourne RB, Rorabeck
CH, Kim P, Hardie R, Kramer J, Kirkley A. What is the best way of assessing
outcome after total knee replacement? Clin Orthop Relat Res.1996;331:
221-5.331221
1996
[PubMed][CrossRef]
Zahiri CA, Schmalzried TP, Szuszczewicz
ES, Amstutz HC. Assessing activity in joint replacement patients. J
Arthroplasty.1998;13:
890-5.13890
1998
[CrossRef]
Schmalzried TP, Shepherd EF, Dorey FJ,
Jackson WO, dela Rosa M, Fa'vae F, McKellop HA, McClung CD, Martell J,
Moreland JR, Amstutz HC. Wear is a function of use, not time. Clin
Orthop Relat Res.2000;381:
36-46.38136
2000
[CrossRef]
Seedhom BB, Wallbridge NC. Walking
activities and wear of prostheses. Ann Rheum Dis.1985;44:
838-43.44838
1985
[PubMed][CrossRef]
Marx RG, Stump TJ, Jones EC, Wickiewicz
TL, Warren RF. Development and evaluation of an activity rating scale for
disorders of the knee. Am J Sports Med.2001;29:
213-8.29213
2001
[PubMed]
Tegner Y, Lysholm J. Rating systems in
the evaluation of knee ligament injuries. Clin Orthop Relat
Res.1985;198:
43-9.19843
1985
LaPorte RE, Montoye HJ, Caspersen CJ.
Assessment of physical activity in epidemiologic research: problems and
prospects. Public Health Rep.1985;100:
131-46.100131
1985
[PubMed]
Amstutz HC, Thomas BJ, Jinnah R, Kim W,
Grogan T, Yale C. Treatment of primary osteoarthritis of the hip. A comparison
of total joint and surface replacement arthroplasty. J Bone Joint Surg
Am.1984;66:
228-41.66228
1984
Lavernia CJ, Sierra RJ, Hungerford DS,
Krackow K. Activity level and wear in total knee arthroplasty: a study of
autopsy retrieved specimens. J Arthroplasty.2001;16:
446-53.16446
2001
[PubMed][CrossRef]
Kuster MS, Stachowiak GW. Factors
affecting polyethylene wear in total knee arthroplasty.
Orthopedics.2002;25(2
Suppl): s235-42.25s235
2002
[PubMed]
Schmalzried TP, Szuszczewicz ES,
Northfield MR, Akizuki KH, Frankel RE, Belcher G, Amstutz HC. Quantitative
assessment of walking activity after total hip or knee replacement. J
Bone Joint Surg Am.1998;80:
54-9.8054
1998
[CrossRef]
Streiner DL, Norman GR, editors.
Health measurement scales: a practical guide to their development and
use. 2nd ed. New York: Oxford University Press;
1995.
1995
Miner AL, Lingard EA, Wright EA, Sledge
CB, Katz JN; Kinemax Outcomes Group. Knee range of motion after total knee
arthroplasty: how important is this as an outcome measure? J
Arthroplasty.2003;18:
286-94.18286
2003
[CrossRef]
Lingard EA, Katz JN, Wright RJ, Wright
EA, Sledge CB; Kinemax Outcomes Group. Validity and responsiveness of the Knee
Society Clinical Rating System in comparison with the SF-36 and WOMAC.
J Bone Joint Surg Am.2001;83:
1856-64.831856
2001
[PubMed]
Irrgang JJ, Anderson AF. Development and
validation of health-related quality of life measures for the knee.
Clin Orthop Relat Res.2002;402:
95-109.40295
2002
[PubMed][CrossRef]
Bellamy N. WOMAC osteoarthritis
index: a user's guide. London, Ontario; 1995.
1995
Saleh K, Nelson C, Kassim R, Yoon P,
Haas S. Total knee arthroplasty in patients on workers' compensation: a
matched cohort study with an average follow-up of 4.5 years. J
Arthroplasty.2004;19:
310-2.19310
2004
[CrossRef]
Byrne BM. Structured equation
modeling with AMOS. Lawrence Erlbaum Associates;
2001.
2001
Blair SN. How to assess exercise habits
and physical fitness. In: Matarazzo JD, Weiss SM, Herd JA, Miller NE, Weiss
SM, editors. Behavioral health: a handbook of health enhancement and
disease prevention. New York: Wiley; 1984. p
424-47.424
1984
Ainsworth BE, Jacobs DR Jr, Leon AS.
Validity and reliability of self-reported physical activity status: the Lipid
Research Clinics questionnaire. Med Sci Sports Exerc.1993;25:
92-8.2592
1993
[PubMed][CrossRef]
Blair SN, Haskell WL, Ho P, Paffenbarger
RS Jr, Vranizan KM, Farquhar JW, Wood PD. Assessment of habitual physical
activity by a seven-day recall in a community survey and controlled
experiments. Am J Epidemiol.1985;122:
794-804.122794
1985
[PubMed]
Chasan-Taber S, Rimm EB, Stampfer MJ,
Spiegelman D, Colditz GA, Giovannucci E, Ascherio A, Willett WC.
Reproducibility and validity of a self-administered physical activity
questionnaire for male health professionals. Epidemiology.1996;7:
81-6.781
1996
[PubMed][CrossRef]
Jacobs DR Jr, Ainsworth BE, Hartman TJ,
Leon AS. A simultaneous evaluation of 10 commonly used physical activity
questionnaires. Med Sci Sports Exerc.1993;25:
81-91.2581
1993
[PubMed][CrossRef]
Wolf AM, Hunter DJ, Colditz GA, Manson
JE, Stampfer MJ, Corsano KA, Rosner B, Kriska A, Willett WC. Reproducibility
and validity of a self-administered physical activity questionnaire.
Int J Epidemiol.1994;23:
991-9.23991
1994
[PubMed][CrossRef]
Voorrips LE, Ravelli AC, Dongelmans PC,
Deurenberg P, Van Staveren WA. A physical activity questionnaire for the
elderly. Med Sci Sports Exerc.1991;23:
974-9.23974
1991
[PubMed]
Taylor CB, Coffey T, Berra K, Iaffaldano
R, Casey K, Haskell WL. Seven-day activity and self-report compared to a
direct measure of physical activity. Am J Epidemiol.1984;120:
818-24.120818
1984
[PubMed]
Singh PN, Tonstad S, Abbey DE, Fraser
GE. Validity of selected physical activity questions in white Seventh-day
Adventists and non-Adventists. Med Sci Sports Exerc.1996;28:
1026-37.281026
1996
[PubMed]
Sallis JF, Haskell WL, Wood PD, Fortmann
SP, Rogers T, Blair SN, Paffenbarger RS Jr. Physical activity assessment
methodology in the Five-City Project. Am J Epidemiol.1985;121:
91-106.12191
1985
[PubMed]
Ainsworth BE, Leon AS, Richardson MT,
Jacobs DR, Paffenbarger RS Jr. Accuracy of the College Alumnus Physical
Activity Questionnaire. J Clin Epidemiol.1993;46:
1403-11.461403
1993
[PubMed][CrossRef]
Kohl HW, Blair SN, Paffenbarger RS Jr,
Macera CA, Kronenfeld JJ. A mail survey of physical activity habits as related
to measured physical fitness. Am J Epidemiol.1988;127:
1228-39.1271228
1988
[PubMed]
Washburn RA, Adams LL, Haile GT.
Physical activity assessment for epidemiologic research: the utility of two
simplified approaches. Prev Med.1987;16:
636-46.16636
1987
[PubMed][CrossRef]
Washburn RA, Goldfield SR, Smith KW,
McKinlay JB. The validity of self-reported exercise-induced sweating as a
measure of physical activity. Am J Epidemiol.1990;132:
107-13.132107
1990
[PubMed]
Ewald FC. The Knee Society total knee
arthroplasty roentgenographic evaluation and scoring system. Clin
Orthop Relat Res.1989;248:
9-12.2489
1989
Charnley J. Low friction
arthroplasty of the hip: theory and practice. New York: Springer;
1979.
1979
Harris WH. Traumatic arthritis of the
hip after dislocation and acetabular fractures: treatment by mold
arthroplasty. An end-result study using a new method of result evaluation.
J Bone Joint Surg Am.1969;51:
737-55.51737
1969
[PubMed]
Insall JN, Dorr LD, Scott RD, Scott WN.
Rationale of the Knee Society clinical rating system. Clin Orthop Relat
Res.1989;248:
13-4.24813
1989
Johnston RC, Fitzgerald RH Jr, Harris
WH, Poss R, Muller ME, Sledge CB. Clinical and radiographic evaluation of
total hip replacement. A standard system of terminology for reporting results.
J Bone Joint Surg Am. 1990;72:161-8. Erratum in: J Bone Joint Surg
Am.1991;73:
952.73952
1991
Weiss JM, Noble PC, Conditt MA, Kohl HW,
Roberts S, Cook KF, Gordon MJ, Mathis KB. What functional activities are
important to patients with knee replacements? Clin Orthop Relat
Res.2002;404:
172-88.404172
2002
[CrossRef]
Healy WL, Iorio R, Lemos MJ. Athletic
activity after total knee arthroplasty. Clin Orthop Relat Res.2000;380:
65-71.38065
2000
[PubMed][CrossRef]
Chandler HP, Reineck FT, Wixson RL,
McCarthy JC. Total hip replacement in patients younger than thirty years old.
A five-year follow-up study. J Bone Joint Surg Am.1981;63:
1426-34.631426
1981
[PubMed]
McClung CD, Zahiri CA, Higa JK, Amstutz
HC, Schmalzried TP. Relationship between body mass index and activity in hip
or knee arthroplasty patients. J Orthop Res.2000;18:
35-9.1835
2000
[PubMed][CrossRef]
Voorrips LE, Lemmink KA, van Heuvelen
MJ, Bult P, van Staveren WA. The physical condition of elderly women differing
in habitual physical activity. Med Sci Sports Exerc.1993;25:
1152-7.251152
1993
[PubMed]
Foran JR, Mont MA, Etienne G, Jones LC,
Hungerford DS. The outcome of total knee arthroplasty in obese patients.
J Bone Joint Surg Am.2004;86:
1609-15.861609
2004
[PubMed]
Foran JR, Mont MA, Rajadhyaksha AD,
Jones LC, Etienne G, Hungerford DS. Total knee arthroplasty in obese patients:
a comparison with a matched control group. J Arthroplasty.2004;19:
817-24.19817
2004
[PubMed][CrossRef]
Kirshner B, Guyatt G. A methodological
framework for assessing health indices. J Chronic Dis.1985;38:
27-36.3827
1985
[PubMed][CrossRef]