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QUESTIONNAIRE ON THE PERCEPTIONS OF PATIENTS ABOUT TOTAL HIP REPLACEMENT JILL DAWSON,

RAY FITZPATRICK,

ANDREW CARR,

DAVID MURRAY

From the University of Oxford and the Nuffield Orthopaedic Centre, Oxford, England

We developed a 12-item questionnaire for completion by patients having total hip replacement (THR). A prospective study of 220 patients was undertaken before operation and at follow-up six months later. Each completed the new questionnaire as well as the SF36, and some the Arthritis Impact Measurement Scales (AIMS). An orthopaedic surgeon assessed the Charnley hip score. The single score derived from the questionnaire had a high internal consistency. Reproducibility was examined by test-retest reliability and was found to be satisfactory. The validity of the questionnaire was established by obtaining significant correlation in the expected direction with the Charnley scores and relevant scales of the SF36 and the AIMS. Sensitivity to change was assessed by analysing the differences between the preoperative scores and those at the follow-up. The standardised effect size for the new questionnaire compared favourably with that for the SF36 and the AIMS. The new questionnaire provides a measure of outcome for THR which is short, practical, reliable, valid and sensitive to clinically important changes. J Bone Joint Surg [Br] 1996;78-B:185-90. Received 9 May 1995; Accepted after revision 13 September 1995

A number of scores have been developed to measure the outcome of total hip replacement (THR). They normally derive from clinical and radiological data and ultimately

J. Dawson, DPhil, Research Officer R. Fitzpatrick, PhD, University Lecturer Department of Public Health and Primary Care, University of Oxford, Gibson Building, Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK. A. Carr, FRCS, Consultant Orthopaedic Surgeon D. Murray, FRCS, Honorary Consultant and Senior Research Fellow, University of Oxford Nuffield Orthopaedic Centre, Windmill Road, Headington, Oxford OX3 7LD, UK. Correspondence should be sent to Dr R. Fitzpatrick. ©1996 British Editorial Society of Bone and Joint Surgery 0301-620X/96/21145 $2.00 VOL. 78-B, NO. 2, MARCH 1996

depend on the judgement of the surgeon (Murray 1993). Patients and surgeons may differ in their concerns and priorities (Wright, Rudicel and Feinstein 1994). It is increasingly recognised that methods are required to elicit the patient’s perception of the outcomes of orthopaedic surgery (Amadio 1993) since it has become clear that the patient can provide reliable and valid judgement of health status and of the benefits of treatment (Fitzpatrick et al 1992). Many questionnaires have been developed which are intended for general use across the widest range of medical and surgical problems and they have provided useful insights when applied to patients receiving THR (Wiklund and Romanus 1991; O’Boyle et al 1992; Cleary et al 1993). They are, however, often quite long and contain items which may not be relevant to a specific problem. Consequently, they may be impracticable for routine use and insensitive to the specific changes in health produced by a particular intervention (Patrick and Deyo 1989). Questionnaires are needed therefore which address patients’ perception of a single disease entity and are maximally sensitive to the outcomes of narrowly-defined groups. Shorter questionnaires may be just as sensitive to changes of importance as longer versions (Katz et al 1992; Fitzpatrick et al 1993) and are better for routine use. We have developed a short questionnaire for use in THR which is reliable, reproducible, valid and sensitive to change. MATERIALS AND METHODS Development of the questionnaire. Initially, we interviewed 20 patients attending an outpatient clinic to identify how they experienced and reported problems with their hips. Subsequently, after reviewing other established questionnaires, we drafted a list of 20 items which was then given to 20 new patients in the clinic. They were also asked to take home a second copy of the questionnaire, complete it the following day and return it in a prepaid envelope. This second copy also allowed them to comment on the questionnaire and to include any hip-related problems not addressed by it. The responses were then reviewed and the questionnaire modified to make the items more reproducible and easier for the patients to understand. Testing of alternative formats was repeated on two additional series of 20 patients until the final version of the questionnaire was agreed. Many of the items in this version resemble ele185

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ments included in other assessments such as the Harris hip score (Harris 1969). Attention was paid to the appearance of the questionnaire as well as to its structure. It contains 12 items each of which has five categories of response (Table I). Each item is scored from 1 to 5, from least to most difficulty or severity. The scores are then added to produce a single figure with a range from 12 (least difficulties) to 60 (most difficulties). We then designed a study to examine whether the new questionnaire was internally consistent, reproducible, valid and sensitive to clinical change (Cox et al 1992). Internal consistency examines whether the items measure a single underlying concept. Reproducibility is concerned with whether the questionnaire yields the same results on repeated trials under the same conditions. Validity defines whether it measures what it purports to measure and can be examined by two methods. Content validity assesses whether items in a questionnaire cover the intended topics clearly. Construct validity, the extent to which the questionnaire supports predefined hypotheses, is determined by whether it produces an anticipated set of relationships with other variables such as the clinical evidence. Sensitivity to change, or responsiveness, reflects the ability to detect clinically significant changes. Between February and mid-August 1994 we recruited 220 consecutive patients into a prospective study from the preadmission assessment clinic at the Nuffield Orthopaedic Centre, Oxford. Two patients refused and three were deemed unsuitable. The remainder completed a variety of assessments at the clinic and again at routine clinic appointments six months after operation. Surgeons were not aware of the questionnaire scores when they carried out the clinical assessments. There were 131 women and 89 men with a median age of 70.5 years (35.8 to 89.6; SD 10.99). Of these, 185 (84.1%) were diagnosed as having advanced, primary osteoarthritis and 12 (5.5%) had osteoarthritis secondary to congenital dysplasia or dislocation. Thirteen (5.9%) had problems after treatment for fractures of the neck of the femur and the remaining nine (4.1%) had previous inflammatory arthritis or osteonecrosis. One patient decided not to proceed with an operation and did not receive a formal diagnosis. Of the 220 patients, 188 had an operation during the period of the study; two (1%) died postoperatively before the follow-up assessment. Of the remaining 32, 24 did not proceed to operation for a variety of reasons and eight had their surgery delayed. Of those undergoing operation 29 (15.6%) had a revision of a previous THR and 157 (84.4%) a primary replacement. Internal consistency. Internal consistency was tested using Cronbach’s alpha (Cronbach 1951) for the initial questionnaire and at follow-up six months after operation. This summarises the internal correlations of all items in a scale. The higher the alpha coefficient (range 0.0 to 1.0) the more consistent is the scale and the greater the likelihood that it

A. CARR,

D. MURRAY

is tapping an underlying single variable on the questionnaire. We examined correlations of all items with the overall score and also whether Cronbach’s alpha was improved by removal of any item. Reproducibility. Reproducibility (test-retest reliability) was assessed by asking 68 patients at the preoperative stage to complete and return a second questionnaire 24 hours later. The data were examined by the coefficient of reliability according to the method of Bland and Altman (1986). Construct validity. This was examined by Pearson correlation coefficients, both preoperatively and at the six-month follow-up, between the total score of the questionnaire and other related measures obtained at the same assessment. We considered that scores for the questionnaire should correlate moderately with Charnley scores rated by an orthopaedic surgeon and with scores from the two other health-status questionnaires completed by the patient (SF36 and the Arthritis Impact Measurement Scales). The Charnley score grades pain, mobility and walking on six-point scales in relation to one hip, with lower scores indicating greater disability (Charnley 1972). Walking is assessed only in patients who have no other condition which may undermine walking ability. The SF36 is a 36-item questionnaire widely used to measure health status (Ware and Sherbourne 1992). It provides scores on physical functioning, social functioning, role limitations due to physical problems, role limitations due to emotional problems, general mental health, energy, bodily pain and general perceptions of health. Scores for each item range from 0 (poor) to 100 (good). The Arthritis Impact Measurement Scales (AIMS) is designed to be used for the assessment of rheumatoid arthritis and not specifically for evaluation of the hip (Meenan, Gertman and Mason 1980). It consists of 45 items over nine aspects of mobility, physical activity, dexterity, household activity, activities of daily living, pain, anxiety, depression and social activities. Scores range from 0 to 10 with higher scores indicating greater incapacity. It has been used in studies of patients after THR (Liang et al 1985; Johanson et al 1992). All patients were asked to complete the study questionnaire and the SF36 both at the preoperative assessment and at the six-month follow-up. In addition, 62 patients were asked to complete the AIMS. Some patients required the help of a relative, friend or the researcher to complete the questionnaires. Sensitivity to change. The sensitivity to change of the study questionnaire was examined by comparing scores before and six months after operation. Scores of 185 patients were available. We calculated effect sizes for the study questionnaire, the SF36 and the AIMS. This is a method of calculating the extent of change measured in a standardised way which allows comparison between questionnaires (Kazis, Anderson and Meenan 1989) and is determined as the difference between the mean preoperative and postoperative scores, THE JOURNAL OF BONE AND JOINT SURGERY

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Table I. Preoperative and postoperative scores obtained using the 12-item hip questionnaire Preop (n = 219)

Postop (n = 185)

Scoring categories

Number

Percentage

Number

1) How would you describe the pain you usually had from your hip?

1 2 3 4 5

None Very mild Mild Moderate Severe

1 3 12 87 116

0.5 1.4 5.5 39.7 53.0

63 60 21 29 13

33.9 32.3 11.3 15.6 7.0

2) Have you had any trouble with washing and drying yourself (all over) because of your hip?

1 2 3 4 5

No trouble at all Very little trouble Moderate trouble Extreme difficulty Impossible to do

26 44 90 48 12

11.8 20.0 41.1 21.8 5.5

85 57 36 4 4

45.7 30.6 19.4 2.2 2.2

3) Have you had any trouble getting in and out of a car or using public transport because of your hip? (whichever you tend to use)

1 2 3 4 5

No trouble at all Very little trouble Moderate trouble Extreme difficulty Impossible to do

9 28 105 69 9

4.1 12.7 48.0 31.4 4.1

81 63 29 11 2

43.5 33.9 15.6 5.9 1.1

4) Have you been able to put on a pair of socks, stockings or tights?

1 2 3 4 5

Yes, easily With little difficulty With moderate difficulty With extreme difficulty No, impossible

9 33 77 69 32

4.1 15.0 35.0 31.4 14.5

63 60 37 12 14

33.9 32.3 19.9 6.5 7.5

5) Could you do the household shopping on your own?

1 2 3 4 5


20 26 50 36 88

9.1 11.8 22.7 16.4 40.0

66 39 25 13 43

35.5 21.0 13.4 7.0 23.1

6) For how long have you been able to walk before the pain from your hip became severe? (with or without a stick)

1 No pain/>30 minutes 2 16 to 30 minutes 3 5 to 15 minutes 4 Around the house only 5 Not at all

27 45 62 57 29

12.3 20.5 28.2 25.9 13.2

118 25 17 18 8

63.4 13.4 9.1 9.7 4.3

7) Have you been able to climb a flight of stairs?

1 2 3 4 5


6 36 88 68 22

2.7 16.4 40.0 30.9 10.0

77 64 30 11 3

41.6 34.6 16.2 5.9 1.6

8) After a meal (sat at a table), how painful has it been for you to stand up from a chair because of your hip?

1 2 3 4 5

Not at all painful Slightly painful Moderately painful Very painful Unbearable

5 31 69 112 3

2.3 14.1 31.4 50.9 1.4

85 76 16 8 0

45.9 41.1 8.6 4.3 0.0

9) Have you been limping when walking, because of your hip?

1 Rarely/never 2 Sometimes or just at first 3 Often, not just at first 4 Most of the time 5 All of the time

3 8 7 50 152

1.4 3.6 3.2 22.7 69.1

44 61 16 23 41

23.8 33.0 8.6 12.4 22.2

36 8 53 64 59

16.4 3.6 24.1 29.1 26.8

127 17 30 1 10

68.6 9.2 16.2 0.5 5.4

2 14 63 106 35

0.9 6.4 28.6 48.2 15.9

81 64 24 13 3

43.8 34.6 13.0 7.0 1.6

13 17 40 64 86

5.9 7.7 18.2 29.1 39.1

114 23 31 11 6

61.6 12.4 16.8 5.9 3.2

Item

Percentage

During the past four weeks

10) Have you had any sudden, severe pain - ‘shooting’, ‘stabbing’ or ‘spasms’ - from the affected hip?

1 2 3 4 5

11) How much has pain from your hip interfered with your usual work (including housework)?

1 Not at all 2 A little bit 3 Moderately 4 Greatly 5 Totally

12) Have you been troubled by pain from your hip in bed at night?

1 2 3 4 5

VOL. 78-B, NO. 2, MARCH 1996

No days Only 1 or 2 days Some days Most days Every day

No nights Only 1 or 2 nights Some nights Most nights Every night

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D. MURRAY

Table II. Internal consistency of the hip questionnaire, preoperatively and postoperatively Preoperative (n = 219)

Postoperative (n = 185)

Content

Mean score (SD)

Item-total correlation

Alpha if item removed

Mean score (SD)

Item-total correlation

Alpha if item removed

1

Usual level of hip pain

4.43

(0.70)

0.56

0.82

2.30

(1.27)

0.59

0.88

2

Trouble with washing and drying

2.89

(1.05)

0.53

0.82

1.84

(0.95)

0.68

0.88

3

Trouble with transport

3.19

(0.86)

0.63

0.82

1.87

(0.96)

0.66

0.88

4

Putting on socks/stockings/tights

3.37

(1.04)

0.42

0.83

2.22

(1.20)

0.58

0.88

5

Doing household shopping alone

3.66

(1.35)

0.54

0.82

2.61

(1.58)

0.58

0.89

6

Walking time before severe pain

3.07

(1.22)

0.45

0.83

1.78

(1.21)

0.61

0.88

7

Difficulty going up stairs

3.29

(0.95)

0.65

0.81

1.91

(0.98)

0.63

0.89

8

Pain on standing up from sitting

3.35

(0.82)

0.55

0.82

1.71

(0.80)

0.66

0.88

9

Limping when walking

4.55

(0.83)

0.28

0.84

2.76

(1.50)

0.49

0.89

10

Sudden, severe pain from hip

3.46

(1.36)

0.45

0.83

1.65

(1.11)

0.58

0.88

11

Work interference due to pain

3.72

(0.84)

0.62

0.82

1.88

(0.99)

0.75

0.88

12

Pain in bed at night

3.88

(1.19)

0.51

0.82

1.77

(1.13)

0.64

0.88

Question

Preoperative Cronbach alpha: 0.84

Postoperative Cronbach alpha: 0.89

divided by the standard deviation of the preoperative scores. An effect size of 1.0 is equivalent to a change of one standard deviation in the sample.

improvement in health status at the six-month follow-up. Effect sizes were larger for the study questionnaire than for any of the scales of the SF36 or the AIMS (Table IV).

RESULTS

DISCUSSION

Table I gives the individual scores obtained for patients before operation and at the six-month follow-up. Before operation, the summed score for the questionnaire had a median value of 44 (16 to 59), a mean of 43.6 (95% CI 42.6 to 44.6), and at follow-up a median value of 22 (12 to 51) and a mean of 24.3 (95% CI 22.9 to 25.6). Internal consistency. Cronbach’s alpha for the study questionnaire was 0.84 at the preoperative assessment (n = 219) and 0.89 at the six-month follow-up (n = 185). All items correlated with the total score at >0.4 at both assessments except item 9 at the preoperative review (Table II). Nevertheless, Cronbach’s alpha was not markedly improved by removal of any item from the score. Reproducibility. In the test-retest sample, the differences between the first and second scores were plotted against their means. The scatter appeared normal and showed the same variability across the range of scores at all levels of disability/severity. The estimated mean (–0.73) of score differences was not significantly different from 0. The coefficient of reliability was calculated as 7.27 using Bland and Altman’s (1986) method and 95% of score differences fell between 0 ± 7.27. Overall, 81% of score differences lay between 0 ± 4. Construct validity. The study questionnaire correlated moderately with Charnley scores both before operation and at follow-up (Table III). There was also significant agreement between the study questionnaire and the scales of the SF36 and the AIMS with related content, particularly in the areas of physical function and pain. Sensitivity to change. Patients reported a very substantial

We have developed and tested a short 12-item questionnaire which patients find easy to complete and which provides reliable, valid and responsive data regarding their

Table III. Correlation between the 12-item hip questionnaire and the Charnley clinical assessment, the SF36 and the AIMS assessments Correlation/coefficient Test

Preoperative (n = 219)

Postoperative (n = 185)

Charnley

Pain Walking† Movement

-0.40* -0.40* -0.15‡

-0.58* -0.57* -0.28*

SF36

Physical Pain Mental health Social function Role-physical Role mental Energy Health perceptions

-0.61* -0.68* -0.34* -0.63* -0.30* -0.33* -0.41* -0.19*

-0.71* -0.57* -0.43* -0.56* -0.47* -0.25* -0.44* -0.31*

AIMS§

Pain Mobility Physical activity Social activity Household activity Activities of daily living Depression Anxiety Dexterity

0.56* 0.48* 0.55* 0.23 0.45* 0.38* 0.38* 0.53* 0.37*

0.59* 0.51* 0.66* 0.03 0.48* 0.54* 0.30 0.52* 0.42*

* p < 0.01 † excludes patients with a second symptomatic hip or impaired ability to walk due to another condition (preop n = 167/postop n = 104) ‡ p < 0.05 § preop n = 62/postop n = 56 THE JOURNAL OF BONE AND JOINT SURGERY

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Table IV. Comparison, by effect size, of the 12-item questionnaire with the SF36 and the AIMS in regard to ability to measure change in the condition of the patients after THR Mean score Test

Preoperative 95% CI

At six month follow-up

95% CI

Effect size

12-item questionnaire (n = 185)

43.55

42.55 to 44.55

24.31

22.91 to 25.61

2.75

SF36 (n = 186 unless otherwise stated) Health perceptions (n = 183) Health change Physical activity (n = 175) Pain Role limitation - physical (n = 180) Role limitation - mental (n = 178) Mental health (n = 183) Energy (n = 182) Social function

74.03 42.88 17.83 30.05 13.74 55.74 70.80 46.68 51.83

72.03 40.23 15.40 27.64 9.98 49.21 68.11 43.39 47.38

75.30 75.94 49.54 65.89 44.31 73.78 78.54 61.70 79.10

72.34 72.29 45.42 62.19 38.59 67.94 76.07 58.62 75.12

to to to to to to to to to

78.26 79.59 53.66 69.59 50.03 79.62 81.01 64.78 83.08

-0.07 -1.80 -1.89 -2.13 -1.18 -0.40 -0.42 -0.66 -0.88

3.82 8.82 5.68 1.87 1.38 4.50 2.26 3.54 2.93

2.90 8.47 5.25 1.56 0.95 2.94 1.85 3.05 2.24

1.27 5.64 2.78 1.22 1.21 3.84 1.63 2.25 2.07

0.62 4.91 2.15 0.83 0.82 3.41 1.26 1.80 1.44


1.92 6.37 3.41 1.61 1.60 4.27 2.00 2.70 2.70

0.72 2.34 1.75 0.55 0.10 0.37 0.40 0.68 0.33

AIMS (n = 56) Mobility Physical activity Pain Household activity Activities of daily living Social activity Depression Anxiety Dexterity

perception of hip problems. The patients had little difficulty in completing it. The items are internally consistent and reproducible and the questionnaire may therefore be considered to have at least as favourable levels of reliability as clinical scores used to assess outcomes (Koran 1975). With regard to content validity, the extent to which items on the questionnaire deal with all relevant aspects of the attribute which they are intending to measure, the items included were derived from exploratory interviews with patients rather than by imposing clinical assumptions. Construct validity was tested by examining the level of agreement of the questionnaire with clinical data and with scales from existing health-status assessments. All correlations were in the expected direction with poorer scores on our hip questionnaire correlating with poorer scores for both Charnley and the SF36 and the AIMS. Correlations were highest in the assessment of pain and physical function. Responsiveness, or sensitivity to clinically important change, is least likely to be examined despite its being of the greatest importance in any form of prospective outcome study (Guyatt, Walter and Norman 1987). When the sensitivity to change of the hip questionnaire was compared with the SF36 and the AIMS the standardised effect size was highest for the study questionnaire, indicating that it could be particularly sensitive to improvements obtained by THR. This is probably because the other two assessments were not developed to be used specifically for the outcome of THR. Our questionnaire may be compared with others which have been successfully applied to the treatment of osteoarthritis such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Health Assessment Questionnaire (HAQ). One advantage of our VOL. 78-B, NO. 2, MARCH 1996



76.83 42.88 20.26 32.46 17.50 62.27 73.49 49.97 56.28

4.70 9.17 6.11 2.18 1.81 6.06 2.67 4.03 2.93

questionnaire is that it is intended specifically for use with hip surgery and it is simpler and quicker to process (Bellamy et al 1988; Kirwan et al 1994). It is designed to assess outcomes solely from the viewpoint of the patient and is intended to supplement, not replace, conventional measures of outcome. It is becoming increasingly clear, however, that systematic studies are required to examine effects on outcomes of alternative prostheses, surgical techniques and methods of fixation in orthopaedic surgery (Murray, Carr and Bulstrode 1993). Because variations in outcomes may be quite modest, such studies will need large sample sizes to detect differences and will have to be multicentred. Standardised patient-based measures of outcome have advantages, particularly if they are highly sensitive to clinical change. Similarly, a long period of follow-up is required to detect differences in outcome for THR and simple questionnaires may make such long-term studies more feasible, particularly if the responses can be obtained by post. We acknowledge the contribution of Dr P. Yudkin in providing statistical advice. We also wish to thank all orthopaedic consultants and surgical staff at the Nuffield Orthopaedic Centre who allowed their patients to be included in this study, the nursing staff in preadmission and outpatient clinics, and also the individual patients for giving their time. Financial support was provided by a grant from Oxford Regional Health Authority (Audit). No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. REFERENCES Amadio PC. Editorial. Outcomes measurement: more questions; same answers. J Bone Joint Surg [Am] 1993;75-A:1583-4. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833-40.

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