The Journal of Bone and Joint Surgery (American). 2005;87:1985-1994.
doi:10.2106/JBJS.D.02564
© 2005 The Journal of Bone and Joint Surgery, Inc.
Development and Validation of a Lower-Extremity Activity Scale
Use for Patients Treated with Revision Total Knee Arthroplasty
Khaled J. Saleh, MD, MSc, FRCS(C)1,
Kevin J. Mulhall, MB, MCh, FRCSI(Tr&Orth)1,
Boris Bershadsky, PhD2,
Hassan M. Ghomrawi, MPH2,
Laura E. White, MD3,
Cathy M. Buyea, MS3 and
Kenneth A. Krackow, MD3
1 Department of Orthopaedic Surgery, University of Virginia, 400 Ray C. Hunt
Drive, Suite 330, Charlottesville, VA 22903. E-mail address for K.J. Saleh:
kjs3x{at}hscmail.mcc.virginia.edu
2 Division of Health Services Research and Policy and Administration, School of
Public Health and Clinical Outcomes Research Center, University of Minnesota,
D351 Mayo (MMC 197), Minneapolis, MN 55455
3 State University of New York at Buffalo, Kaleida Health, Buffalo General
Hospital, 100 High Street, Buffalo, NY 14203
Investigation performed at the State University of New York at Buffalo,
Buffalo, New York, the University of Minnesota, Minneapolis, Minnesota, and
the University of Virginia, Charlottesville, Virginia
In support of their research or preparation of this manuscript, one or more
of the authors received grants or outside funding from the Royal College of
Surgeons in Ireland, Stryker Orthopaedics, Orthopaedic Research and Education
Foundation, the American Geriatric Society, the Knee Society, and the
Minnesota Medical Foundation. In addition, one or more of the authors received
payments or other benefits or a commitment or agreement to provide such
benefits from commercial entities (Stryker Orthopaedics and Smith and Nephew).
Also, a commercial entity (Stryker Orthopaedics) paid or directed, or agreed
to pay or direct, benefits to a research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.
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.

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