Responsiveness of observational and self-report methods for assessing disability in mobility in patients with osteoarthritis

The predictors to self-reported and performance-based physical function in knee osteoarthritis patients: a cross-sectional study

Background

Osteoarthritis (OA) knee patients have limited ability in physical function, or difficulties with physical tasks and activities may develop disability. This study aimed to observe the predictors of self-reported and performance-based physical function in patients with knee OA by analyzing the impacts of demographic, pathological, and muscle impairment factors.

Methods

135 knee OA patients participated in this study to complete self-reported questionnaires using Knee Injury and Osteoarthritis Outcome Score (KOOS). When measuring performance-based physical function, a 6-meter gait speed (6MGS) test was measured to evaluate their mobility, and a 5-time Sit-to-Stand test (5STS) was assessed to evaluate their balance. Pain intensity, knee extensor and flexor muscle strength, age, body mass index (BMI), durations of symptoms, and radiographic severity were also collected. Spearman correlation and stepwise multiple linear regression were used to explore the association and predictors in self-reported and performance-based physical function.

Results

BMI and durations of symptoms did not indicate any significant correlation with either self-reported or performance-based physical function. Age is significantly negatively associated with 6MGS (r 2 = -0.383, p < 0.01), while knee extensor muscle strength has a moderate correlation with 5STS (r 2 = -0.528, p < 0.01). In the stepwise multiple linear regression models, pain intensity (β = 0.712, p < 0.001), knee flexor muscle strength (β = 0.112, p = 0.042) were significantly associated with self-reported physical function in daily activities and contributed to 55.0% of the variance in KOOS-PF score. Knee muscle strength, including knee extensor (5STS: β = -0.428, p < 0.001) and flexor muscle strength (6MGS: β = 0.367, p < 0.001), were the main predictors with performance-based physical function.

Conclusion

Pain intensity was the leading risk factor of self-reported physical function, and knee flexor muscle strength contributed as well. The severity of knee OA, durations of symptoms and BMI did not contribute to physical function. However, knee extensor and flexor muscle strength were the main predictors of performance-based performance. Our results show that strengthening of weak knee muscles in both quadriceps and hamstring muscle strength should be considered a priory consideration in knee OA no matter if people are in the early or end-stage of knee OA.

Effect of Context Specificity on Response to the Shortened WOMAC Function Scale in Patients Undergoing Total Knee Arthroplasty

OBJECTIVE

To determine, in patients undergoing total knee arthroplasty (TKA), whether increasing context specificity of selected items of the shortened version of the Western Ontario and McMaster Universities Osteoarthritis Index function (WOMAC-F) scale (ShortMAC-F) (1) enhanced the convergent validity of the ShortMAC-F with performance-based mobility measures (ii) affected mean scale score, structural validity, reliability, and interpretability.

DESIGN

Secondary analysis of randomized clinical trial data.

SETTING

A tertiary teaching hospital.

PARTICIPANTS

Patients undergoing TKA (N=114).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The ShortMAC-F was modified by specifying the "ascending stairs" and "rising from sitting" items to enquire about difficulty in performing the tasks without reliance on compensatory strategies, whereas the modified "level walking" item enquired about difficulty in walking 400 m. Before and 12 weeks after TKA, patients completed the WOMAC-F questionnaire, modified ShortMAC-F questionnaire, knee pain scale questionnaire, sit-to-stand test, fast gait speed test, and stair climb test. Interpretability was evaluated by calculating anchor-based substantial clinical benefit estimates.

RESULTS

The modified ShortMAC-F correlated significantly more strongly than ShortMAC-F or WOMAC-F with pooled performance measures (differences in correlation values, 0.12-0.14). Increasing item context specificity of the ShortMAC-F did not influence its psychometric properties of unidimensionality (comparative fit and Tucker-Lewis indices, >0.95; root mean square error of approximation, 0.05-0.08), reliability (Cronbach's α, 0.75-0.83), correlation with pain intensity (correlation values, 0.48-0.52), and substantial clinical benefit estimates (16 percentage points); however, it resulted in lower mean score (4.5-4.8 points lower).

CONCLUSIONS

The modified ShortMAC-F showed sufficient measurement properties for clinical application, and it seemed more adept than WOMAC-F at correlating with performance-based measures in TKA.

Measurement properties of the OARSI core set of performance-based measures for hip osteoarthritis: a prospective cohort study on reliability, construct validity and responsiveness in 90 hip osteo-arthritis patients

Background and purpose - Improvement of physical function is one of the main treatment goals in severe hip osteoarthritis (OA) patients. The Osteoarthritis Research Society International (OARSI) has identified a core set of performance-based tests to assess the construct physical function: 30-s chair stand test (30-s CST), 4x10-meter fast-paced walk test (40 m FPWT), and a stair-climb test. Despite this recommendation, available evidence on the measurement properties is limited. We evaluated the reliability, validity, and responsiveness of these performance-based measures in patients with hip OA scheduled for total hip arthroplasty (THA). Patients and methods - Baseline and 12-month follow-up measurements were prospectively obtained in 90 end-stage hip OA patients who underwent THA. As there is no gold standard for comparison, the hypothesis testing method was used for construct validity and responsiveness analysis. A test can be assumed valid if ≥75% of predefined hypotheses are confirmed. A subgroup (n = 30) underwent test-retest measurements for reliability analysis. The Oxford Hip Score, Hip injury and Osteoarthritis Outcome Score-Physical Function Short Form, pain during activity score, and muscle strength were used as comparator instruments. Results - Test-retest reliability was appropriate; intraclass correlation coefficient values exceeded 0.70 for all 3 tests. None of the performance-based measures reached 75% hypothesis confirmation for the construct validity or responsiveness analysis. Interpretation - The performance-based tests have good reliability in the assessment of physical function. Construct validity and responsiveness, using patient-reported measures and muscle strength as comparator instruments, could not be confirmed. Therefore, our findings do not justify their use for clinical practice.

Impact of Balance Confidence on Daily Living Activities of Older People with Knee Osteoarthritis with Regard to Balance, Physical Function, Pain, and Quality of Life - A Preliminary Report

OBJECTIVES

The objective of this study was to explore the impact of balance confidence on different activities of daily living (ADL) in older people with knee osteoarthritis (OA).

METHODS

Forty-seven consecutive participants with knee OA were included in this cross-sectional study. They were divided according to the results of the Activities-specific Balance Confidence (ABC) Scale into a group with a low level of confidence in physical functioning (ABC < 50, n = 22) and a group with moderate and high levels of confidence (ABC ≥ 50, n = 25).

RESULTS

In the ABC < 50 group, the effect of pain on ADL, the physician's global assessment of the disease, and the Western Ontario and McMaster Universities Osteoarthritis Index scores were significantly higher, while quality of life (Short form-36) was lower compared to the ABC ≥ 50 group. No significant difference was found between the two groups regarding the static and dynamic balance measurements.

CONCLUSIONS

Older people with knee OA who were less confident in their daily physical activities had more physical difficulties and a greater effect of pain on ADL, lower quality of life, and a higher physician's global assessment, but no differences were obtained in balance tests.

CLINICAL IMPLICATIONS

In people with knee OA, decreased balance confidence is associated with more physical difficulties, an increased effect of pain on ADL, and lower quality of life. An improved awareness of decreased balance confidence may lead to more effective management of older people with knee OA by improving their mobility and QOL through rehabilitation. Furthermore, future research in that direction is warranted.

Relationship between physical performance and self-reported function in healthy individuals across the lifespan

BACKGROUND

Functional outcome measures in clinical trials of musculoskeletal conditions need to be meaningful to individuals.

OBJECTIVES

To investigate the relationship between physical performance and self/proxy-reported function in 1000 healthy children and adults.

DESIGN

Cross-sectional observational study (1000 Norms Project).

METHODS

One thousand males and females aged 3-101 years, healthy by self-report and without major physical disability, were recruited. Twelve performance-based tests were analysed: vertical and long jump, two hand dexterity tests, four balance tests, stepping reaction time, 30-second chair stand, timed up-and-down stairs, and six-minute walk. Self/proxy-reported function was assessed using the Infant-Toddler Quality of Life questionnaire, Child Health Questionnaire, Assessment of Quality of Life (AQoL)-6D Adolescent, AQoL-8D, International Physical Activity Questionnaire and work ability question. Bivariate and multivariate correlational analyses were constructed for infants (3-4y), children (5-10y), adolescents (11-17y), adults (18-59y) and older adults (60+).

RESULTS/FINDINGS

Socio-demographic characteristics were similar to the Australian population. Among infants/children, greater jump and sit-to-stand performance correlated with higher proxy-reported function (p < 0.05). There were no significant relationships observed for adolescents (p > 0.05). Greater jump, dexterity, balance, reaction time, sit-to-stand, stair-climbing and six-minute walk performance correlated with higher self-reported function in adults (r = -0.097 to.231; p < 0.05) and older adults (r = -0.135 to 0.625; p < 0.05). Multivariate regression modelling revealed a collection of independent performance measures explaining up to 46% of the variance in self/proxy-reported function.

CONCLUSIONS

Many performance-based tests were significantly associated with self/proxy-reported function. We have identified a set of physical measures which could form the basis of age-appropriate functional scales for clinical trials of musculoskeletal conditions.

Measuring function after hip and knee surgery: the evidence to support performance-based functional outcome tasks

Accurate, reproducible outcome measures are essential for the evaluation of any orthopaedic procedure, in both clinical practice and research. Commonly used patient-reported outcome measures (PROMs) have drawbacks such as 'floor' and 'ceiling' effects, limitations of worldwide adaptability and an inability to distinguish pain from function. They are also unable to measure the true outcome of an intervention rather than a patient's perception of that outcome. Performance-based functional outcome tools may address these problems. It is important that both clinicians and researchers are aware of these measures when dealing with high-demand patients, using a new intervention or implant, or testing a new rehabilitation protocol. This article provides an overview of some of the clinically-validated performance-based functional outcome tools used in the assessment of patients undergoing hip and knee surgery.

Development and validation of the computer-administered animated activity questionnaire to measure physical functioning of patients with hip or knee osteoarthritis

BACKGROUND

Physical functioning of patients with hip or knee osteoarthritis is measured by self-report questionnaires and performance-based tests. However, performance-based tests often are not feasible.

OBJECTIVE

The aim of this study was to develop a computer-administered questionnaire (ie, the Animated Activity Questionnaire [AAQ]) to measure physical functioning in patients with hip or knee OA. By showing animations of activities, the influence of the patient's own reference frame is minimized. The AAQ measures the same aspects of physical functioning as performance-based tests do.

DESIGN

This was a development and preliminary validation (cross-sectional) study.

METHODS

A pilot version of the AAQ was developed using motion capture to analyze the movement of a person performing 7 daily activities. Different animations of the same activity were made with 2 to 5 levels of difficulty. For each activity, participants were asked to choose one animation that best corresponds to their own way of performing the activity. A preliminary validation study was performed to compare the AAQ with validated self-report questionnaires (Knee Injury and Osteoarthritis Outcome Score, Hip Disability and Osteoarthritis Outcome Score, and questionnaires on walking, stair climbing, and rising and sitting down) and performance-based tests (walking, Timed "Up & Go" Test, Timed Stair Test) in 33 patients with hip or knee osteoarthritis.

RESULTS

As expected, the AAQ showed a correlation above .70 (.79, 95% confidence interval=.61-.89) with the total score of the performance-based tests. On the subscore level, the results were partly as expected. Fifty-eight percent of the participants preferred the AAQ over self-report questionnaires and performance-based tests.

LIMITATIONS

The findings need to be replicated in larger samples of patients because the sample size of the study was rather small.

CONCLUSION

The AAQ might be a good alternative for measuring physical functioning of patients with hip or knee osteoarthritis. The AAQ can easily be adapted for use in other patient populations. However, further development and validation are needed.

Correlation of Self-Reported Questionnaire (KOOS) with Some Objective Measures in Primary OA Knee Patients

Purpose. Objective of the present study was to see the correlation of subjectively measured KOOS questionnaire with objectively measured 6-minute walk test (6-MWT), age, height, weight, and BMI. Participants. 251 subjects with OA knee based on American College of Rheumatology criteria. Methods. After passing inclusion and exclusion criteria, the following parameters were recorded: age, height, weight, and BMI. Then subjects were asked to fill KOOS questionnaire; then all subjects were asked to do self-paced walk for 6 minutes. Analysis. Spearman rank test was done to see the correlation. Significant level was set at P < 0.05. Results. 6-MWT had a weak correlation with KOOS-ADL (rho 0.461) and strong correlation with KOOS-symptom, KOOS-pain, and KOOS-sports and very strong correlation with KOOS-QOL. BMI had a strong correlation with KOOS-pain, KOOS-symptom, KOOS-ADL, and KOOS-sports and very strong correlation with KOOS-QOL. Weight had a weak correlation with KOOS-symptom, KOOS-ADL, and KOOS-sports and strong correlation with KOOS-pain and KOOS-QOL. All the above values were significant with P < 0.001. Conclusion. KOOS is strongly positively correlated with 6-MWT and negatively correlated with BMI. Its correlation strength has decreased with weight.

Measurement properties of performance-based measures to assess physical function in hip and knee osteoarthritis: a systematic review

OBJECTIVES

To systematically review the measurement properties of performance-based measures to assess physical function in people with hip and/or knee osteoarthritis (OA).

METHODS

Electronic searches were performed in MEDLINE, CINAHL, Embase, and PsycINFO up to the end of June 2012. Two reviewers independently rated measurement properties using the consensus-based standards for the selection of health status measurement instrument (COSMIN). "Best evidence synthesis" was made using COSMIN outcomes and the quality of findings.

RESULTS

Twenty-four out of 1792 publications were eligible for inclusion. Twenty-one performance-based measures were evaluated including 15 single-activity measures and six multi-activity measures. Measurement properties evaluated included internal consistency (three measures), reliability (16 measures), measurement error (14 measures), validity (nine measures), responsiveness (12 measures) and interpretability (three measures). A positive rating was given to only 16% of possible measurement ratings. Evidence for the majority of measurement properties of tests reported in the review has yet to be determined. On balance of the limited evidence, the 40 m self-paced test was the best rated walk test, the 30 s-chair stand test and timed up and go test were the best rated sit to stand tests, and the Stratford battery, Physical Activity Restrictions and Functional Assessment System were the best rated multi-activity measures.

CONCLUSION

Further good quality research investigating measurement properties of performance measures, including responsiveness and interpretability in people with hip and/or knee OA, is needed. Consensus on which combination of measures will best assess physical function in people with hip/and or knee OA is urgently required.

Functional capacity evaluation in subjects with early osteoarthritis of hip and/or knee; is two-day testing needed?

INTRODUCTION

The Work Well Functional Capacity Evaluation (WW FCE) is a two-day performance based test consisting of several work-related activities. Three lifting and carrying test items may be performed on both days. The objective of this study was to assess the need for repeated testing of these items in subjects with early osteoarthritis of the hip and/or the knee and to analyze sources of variation between the 2 days of measurement.

METHODS

A standardized WW FCE protocol was applied, including repeated testing of lifting low, lifting overhead and carrying. Differences and associations between the 2 days were calculated using paired samples t-tests, intraclass correlation coefficients (ICC) and limits of agreement (LoA). Possible sources of individual variation between the 2 days were identified by Wilcoxon signed ranks tests. Pearson correlation coefficients were calculated for differences in performances between days and differences in possible sources of variation between days.

RESULTS

Seventy-nine subjects participated in this study, their mean (SD) age was 56.6 (4.8) years, median (min-max) WOMAC (Western Ontario and McMaster Universities) index scores for pain, stiffness and physical function were 5 (0-17), 3 (0-7) and 14 (0-49), respectively. Median (min-max) SF36 physical function was 75 (5-95), and SF36 pain score was 67 (12-76). Mean performance differences ranged from -0.2 to -0.8 kg (P > 0.05). ICC's ranged from 0.75 (lifting overhead) to 0.88 (lifting low). LoA were: lifting low 8.0 kg; lifting overhead 6.5 kg; carrying 9.0 kg. Pearson's correlations were low and non-significant.

CONCLUSIONS

All three tests show acceptable two-day consistency. WW FCE testing on two consecutive days is not necessary for groups of subjects with early osteoarthritis. Individual sources of variation could not be identified.

Physical functioning before and after total hip arthroplasty: perception and performance

BACKGROUND AND PURPOSE

Self-report and performance-based measures of physical functioning in people before and after total hip arthroplasty seem to present different information. The relationship between these different measures is not well understood, and little information is available about changes in this relationship over time. The aims of this study were: (1) to determine the relationship between self-report and performance-based measures of physical functioning before and after total hip arthroplasty, (2) to assess the influence of pain on the relationship, and (3) to determine whether the relationship changes over time.

SUBJECTS AND METHODS

Seventy-five subjects admitted for total hip arthroplasty were included and examined before and 6 and 26 weeks after surgery. The relationships between the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical functioning subscale and walking speed and gait variability were examined by use of generalized estimating equations, which included interactions with time and the WOMAC pain subscale.

RESULTS

The relationship between self-report and performance-based measures of physical functioning was poor. Pain appeared to have a considerable influence on self-reported physical functioning. The relationship did not appear to change over time.

DISCUSSION AND CONCLUSION

The influence of pain on self-reported physical functioning serves as an explanation for the poor relationship between self-reported and performance-based physical functioning. When using a self-report measure such as the WOMAC, one should realize that it does not seem to assess the separate constructs--physical functioning and pain--that are claimed to be measured.

Actual everyday physical activity in patients with end-stage hip or knee osteoarthritis compared with healthy controls

OBJECTIVE

Few data are available on the level of actual physical activity in patients with osteoarthritis (OA) of the hip and knee. The aim of this study was to measure the level of actual physical activity of patients with end-stage OA of the hip and the knee, to compare this with that of matched healthy controls, and to analyze the data in order to ascertain the factors of influence.

METHOD

The actual physical activity was measured with an activity monitor (AM) in 40 hip and 44 knee OA patients, and compared with measurements obtained from healthy controls. Data were also collected on pain and psychological aspects as anxiety, depression and mental functioning. The primary outcome parameter of the actual physical activity was the percentage of movement-related activity.

RESULTS

The percentage of movement-related activity did not differ between the two OA groups. It was 8.8 (4.2)% for the hip and 8.1 (3.8)% for the knee OA patients. The matched controls were significantly higher movement-related active than OA patients (about 11.0 (2.9)%). Increasing age and body mass index were negatively associated with the percentage of movement-related activity (beta=-0.29 and beta=-0.25, respectively), whereas mental functioning was positively related (beta=0.30).

CONCLUSION

The impact of end-stage OA on the level of actual physical activity is equal for hip and knee OA patients. The actual physical activity for both of the OA groups was significantly and clinically relevantly lower compared to controls. However, this difference was smaller than expected and less dominant than patients' perception of limitations in daily life. Clinicians must be aware that the patients' perception of physical functioning in daily life does not always correspond to the actual physical activity.

Self-reported physical functioning was more influenced by pain than performance-based physical functioning in knee-osteoarthritis patients

BACKGROUND AND OBJECTIVES

To test the hypothesis that self-reported physical functioning is more influenced by pain than performance-based physical functioning.

METHODS

163 knee-osteoarthritis patients completed the performance-based DynaPort KneeTest (DPKT), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and SF-36 (self-report measures of pain and physical functioning) before, 3, 6, and 12 months after knee replacement.

RESULTS

Correlations between (two) self-reported measures of functioning and (two) pain measures were higher (0.57-0.74) than correlations between the performance-based measure of functioning and the two pain measures (0.20 and 0.26). In factor analysis, WOMAC and SF-36 pain and physical functioning subscores loaded on the first factor (eigenvalue 3.2), while DPKT KneeScore2 loaded on the second factor (eigenvalue 0.92). Before surgery, correlations between performance-based and self-reported physical functioning were higher in patients with less pain (0.43) compared to patients with more pain (0.17), for the WOMAC (as expected), but not for the SF-36. After surgery, when the pain had diminished, the correlations between performance-based and self-reported physical functioning were higher, especially for the WOMAC.

CONCLUSIONS

Our hypothesis was convincingly supported by the results of the WOMAC, and somewhat less by the results of the SF-36. We consider this as evidence for a lack of content validity of the WOMAC.

Performance-based methods for measuring the physical function of patients with osteoarthritis of the hip or knee: a systematic review of measurement properties

OBJECTIVE

To systematically review the measurement properties (i.e. internal consistency, reproducibility, validity, responsiveness and interpretability) of all performance-based methods which have been used to measure the physical function of patients with osteoarthritis of the hip or knee.

METHODS

A systematic search was conducted in Medline, CINAHL, PsychINFO and Embase. Standardized criteria were applied to assess the quality of the clinimetric studies and the measurement properties.

RESULTS

Twenty-six performance-based methods were included: 13 walking tests, two stair-climb tests, one chair test and ten multi-item tests. Three out of seven multi-activity tests were tested for internal consistency and two were rated positively. Fourteen tests were tested for reliability and five were rated positively. The absolute measurement error (agreement) was assessed for 10 tests. Only one test received a positive rating. Fourteen tests were tested for construct validity. Only two tests received positive ratings. Responsiveness was assessed for 12 tests, but none of them received a positive rating. A lot of indeterminate ratings were given, mostly for small studies or non-optimal analyses.

CONCLUSION

Many more well-designed studies are needed to assess the measurement properties of performance-based methods. More importantly, however, before one can make a justified choice of a particular performance-based method, consensus is needed on what activities should be included in a performance-based test for patients with hip or knee osteoarthritis and which aspects of function should be measured.

A comparison of the OARSI response criteria with patient's global assessment in patients with osteoarthritis of the hip treated with a non-pharmacological intervention

OBJECTIVE

To compare the Osteoarthritis Research Society International (OARSI) response criteria for clinical trials with patient's global assessment in patients with osteoarthritis (OA) of the hip receiving a non-pharmacological intervention, i.e., manual therapy or exercise therapy.

METHODS

Data of a randomized clinical trial on manual therapy and exercise therapy in patients with OA of the hip (n = 109) were used. Change scores of measures of hip function, range of joint motion and pain were compared between patients who were differently classified by the OARSI response criteria and the patient's global assessment (using a t test, 95% CI). Furthermore, risk ratios (with 95% CI) were calculated for the contrast between treatment outcome, using the OARSI criteria or patient's global assessment.

RESULTS

Few patients were classified as improved (i.e., responders) with the OARSI response criteria as compared to patient's global assessment. Significantly worse outcome for hip function and pain was observed in patients who were classified as non-responders (OARSI criteria), but who considered themselves as improved (patient's global assessment). Risk ratios for the contrast between the two treatment programs (manual therapy vs exercise therapy) were similar, when using the OARSI criteria or patient's global assessment.

CONCLUSION

The validity of the OARSI response criteria has been previously demonstrated in OA patients treated with pharmacological interventions. The present study demonstrates the validity of the OARSI response criteria in OA patients treated with a non-pharmacological intervention, i.e., manual therapy and exercise therapy.

Performance measures were necessary to obtain a complete picture of osteoarthritic patients

OBJECTIVES

Self-report questionnaires and performance measures represent two methods for assessing physical function. A recurring theme is that self-report measures are superior to performance measures. This study investigated the association between three performance test outcomes of four activities (pain, exertion, and time or distance; for self-paced walk, stair test, timed up-and-go, 6-minute walk) with self-reports of physical function (WOMAC Physical Function subscale and LEFS) and the association between the change scores of the performance tests and those of the self-report measures.

STUDY DESIGN AND SETTING

Performance and self-report measures were administered three times (presurgery and at approximately 1 week and approximately 8 weeks post arthroplasty) to 85 patients who underwent total hip or knee arthroplasty. Components of the performance tests were pooled within each domain across the four measures. Multiple regression analyses were applied. Independent variables were performance tests components; dependent variables were self-report measures. Standardized regression coefficients described the cross-sectional and longitudinal associations.

RESULTS

Pain was the principal determinant of WOMAC Physical Function subscale scores. Pain, exertion, and time or distance were strongly associated with the LEFS at the first, second, and third assessments, respectively. Change in pain was most strongly associated with change in self-reported physical function.

CONCLUSION

Our findings caution against the isolated use of self-report assessments of physical function.

Measuring Activity Limitations in Walking: Development of a Hierarchical Scale for Patients With Lower-Extremity Disorders Who Live at Home

OBJECTIVE

To develop a hierarchical scale that measures activity limitations in walking in patients with lower-extremity disorders who live at home.

DESIGN

Cross-sectional study.

SETTING

Orthopedic workshops and outpatient clinics of secondary and tertiary care centers.

PARTICIPANTS

Patients (N=981; mean age +/- standard deviation, 58.6+/-15.4 y; 46% men) living at home, with different lower-extremity disorders: stroke, poliomyelitis, osteoarthritis, amputation, complex regional pain syndrome type I, and diabetic and degenerative foot disorders.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

(1) Fit of the monotone homogeneity model, indicating whether items can be used for measuring patients; (2) fit of the double monotonicity model, indicating invariant (hierarchical) item ordering; (3) intratest reliability, indicating repeatability of the sum score; (4) robustness, addressing the clinimetric properties within subgroups of patients; and (5) differential item functioning, addressing the validity of comparisons between subgroups of patients.

RESULTS

Thirty-five of 41 dichotomous items had (1) good fit of the monotone homogeneity model (coefficient H=.50), (2) good fit of the double monotonicity model (coefficient H(T)=.33), (3) good intratest reliability (coefficient rho=.95), (4) satisfactory robustness (within subgroups of patients defined by age, sex, and diagnosis), and (5) some differential item functioning (6 items in amputees compared with nonamputees).

CONCLUSIONS

A hierarchical scale, with excellent scaling characteristics, was developed to measure activity limitations in walking in patients with lower-extremity disorders who live at home. The measurements should be interpreted cautiously when making comparisons between amputees and nonamputees.

Reproducibility and validity of the DynaPort KneeTest

OBJECTIVE

To determine the reproducibility and validity of the DynaPort KneeTest, a performance-based test that measures quality of movement of patients undergoing total knee replacement (TKR).

METHODS

A total of 92 patients with osteoarthritis (OA) of the knee performed the KneeTest twice on the same day; 94 healthy controls performed the KneeTest once. During the test, 29 activities were performed with accelerometers attached to the body. Relevant functional parameters were extracted from the accelerometers. A selection of parameters was used to calculate activity scores, based on the ability of parameters to discriminate between patients and controls (regression analyses). Based on internal consistency analyses (Cronbach's alpha), redundant activities were removed. Four cluster scores and a total KneeScore were calculated from the remaining activity scores. Reproducibility and validity of the cluster scores and the total KneeScore 2 were assessed.

RESULTS

Based on internal consistency analyses, the test was reduced to 23 activities. Inter- and intraobserver reliability using intraclass correlation coefficients were 0.90 (0.83-0.94) and 0.95 (0.83-0.98), respectively. Limits of inter- and intraobserver agreement were -8.3 to 11.3 and -4.2 to 9.0. Construct validity was confirmed by expected correlations with the Western Ontario and McMaster University Osteoarthritis Index physical functioning (0.55), Medical Outcomes Study Short Form-36 Health Survey physical functioning (0.62), and Knee Society Score function (0.64).

CONCLUSION

The KneeTest is a useful performance-based measure for research in patients with knee OA undergoing TKR, with good reliability and validity. Further research is required to improve its usefulness for clinical practice.

In-hospital outcome and resource use in hip arthroplasty: influence of body mass

To determine the influence of body mass index (BMI) on perioperative morbidity, functional recovery, and hospital use, the records of 207 patients who underwent primary total hip arthroplasty were reviewed and patients were grouped according to BMI. Transfusion requirements, operative complications, functional recovery, and assistance needed for transfers from supine to sit, sit to stand, and bed to chair positions were analyzed at the first physical therapy. Compared with others, morbidly obese patients (BMI > or = 40 kg/m2) had significantly longer mean operative time and higher mean intraoperative blood loss (P<.05), a trend toward more complications, but no significant difference in functional recovery and hospital use.

Comparison of the responsiveness of the Harris Hip Score with generic measures for hip function in osteoarthritis of the hip

OBJECTIVE

To compare responsiveness of the Harris Hip Score with generic measures (that is, the Short Form-36 (SF-36), and a test of walking speed and pain during walking) in patients with osteoarthritis (OA) of the hip.

METHOD

The first 75 cases within the population of a randomised clinical trial on manual therapy and exercise therapy were selected for secondary analysis. Experienced (self reported) recovery by the patients after treatment (five weeks) was used as an external criterion for clinically relevant improvement. Responsiveness was evaluated by comparing responsiveness ratios and receiver operating characteristic curves.

RESULTS

The responsiveness ratio for the Harris Hip Score was high (1.70) compared with walking speed (0.45), pain during walking (0.66), and the subscales of the SF-36-"bodily pain" (0.42) and "physical functioning" (0.36). The area under the curve also was highest for the Harris Hip Score (0.92) compared with walking speed (0.71), pain during walking (0.73), and the SF-36 subscales-bodily pain and physical functioning (both 0.66).

CONCLUSION

The Harris Hip Score is more responsive than the test of walking speed, pain, and subscales for function of the SF-36 in patients with OA of the hip. The Harris Hip Score seems to be a suitable instrument to evaluate change in hip function in patients with OA of the hip.

The relationship between self-report and performance-related measures: questioning the content validity of timed tests

OBJECTIVE

To examine the determinants of the modest correlation between self-report and performance-related measures in patients with osteoarthritis of the hip or knee.

METHODS

Measures included the Lower Extremity Functional Scale (LEFS), the self paced walk, timed up-and-go, and stair test. Each performance measure consisted of 3 domains: time, pain (visual analog scale), and exertion (Borg scale). Activity specificity was assessed by examining correlations between the LEFS with single activity and multiple activity time scores. Domain specificity was examined by comparing correlations between the LEFS and single and multiple domain scores. The impact of measurement error was considered.

RESULTS

Increasing the number of activity time scores had no effect. Forming a composite performance score based on time, pain, and exertion substantially increased the correlation from 0.44 (composite timed score) to 0.59 (pooled domain and activity score) (P = 0.009).

CONCLUSION

Performance scores based on time alone appear to inadequately represent the breadth of health concepts associated with functional status.

Responsiveness of the index of mobility limitation: comparison with gait speed alone in the longitudinal aging study amsterdam

BACKGROUND

Interpreting self-reported disability differences between diverse older populations is complicated by differences in attitudes and environment. We have previously reported on the index of mobility-related limitation tests (MOBLI), and shown that it predicts mortality over 4 years. In this article, we examine whether the index is responsive to changes in self-reported mobility disability.

METHODS

Data on gait speed, time to complete 5 chair stands, and peak expiratory flow rate, with self-reported difficulty walking for 5 minutes, were available from the baseline and two 3-year follow-ups in the Longitudinal Aging Study Amsterdam. Analysis used data on changes in the index (or walking speed alone) and corresponding change over 3 years in self-reported difficulty or inability with a medium-distance walk.

RESULTS

During all follow-ups, groups reporting deterioration in functioning had relatively larger changes in gait speed and MOBLI score than did the "no deterioration" groups. In comparative analyses of responsiveness, the MOBLI score had a larger responsiveness index, higher odds ratios, and larger receiving operating characteristic area than gait speed alone.

CONCLUSIONS

The MOBLI index of mobility-related physical limitation tests is responsive to changes in self-reported mobility disability over two 3-year periods, and performs better than gait speed alone. This property is strongly supportive of its validity for epidemiological comparison of older populations across countries or over longer periods of time.

Mini-incision total hip arthroplasty: a comparative assessment of perioperative outcomes

Compared with patients with total hip arthroplasty (THA) via a direct lateral approach, patients treated with THA via a mini-incision approach had significantly earlier ambulation, less transfer assistance, and more favorable discharge dispositions; they also had decreased transfusion requirements and better functional recovery with early physical therapy. This procedure achieved accurate and reproducible implantation, regardless of patient habitus.