Strengths The survey is easy to administer and relatively easy to score. Considerations The survey takes approximately minutes to complete, which some patients may find difficult.
References Nilsdotter, A. Hip disability and osteoarthritis outcome score HOOS — validity and responsiveness in total hip replacement. For clarity, as per the prior work of Roos et. WOMAC osteoarthritis index. Reliability, validity, and responsiveness in patients with arthroscopically assessed osteoarthritis. Western Ontario and MacMaster Universities.
Scand J Rheumatol. Dimensionality was assessed by performing principal component factor analysis, firstly by entering all 40 items into one analysis, and secondly by performing one analysis for each subscale. Failure to load on a single major factor suggests that the items do not all measure the same aspect.
An eigenvalue criterion of 1. The Hip Disability and Osteoarthritis Outcome Score was developed to assess patient-relevant aspect of hip related problems. Spearman's correlation coefficients r s were calculated to assess construct validity of the HOOS in comparison to the SF It was hypothesized a priori that the correlations to the SF subscales physical function and bodily pain should be high, the correlations to the subscale general health should be low and the correlation to the other subscales, role physical, vitality, social function, role emotional and mental health should be moderate.
Responsiveness was calculated as standardized response mean SRM. SRM is defined as mean score change divided by the standard deviation of that score change [ 18 ]. The sampling distribution mean, standarddeviation of the SRMs of the two measurements was estimated with a jackknife procedure [ 18 ], programmed in SPSS Of the individual items 2. Of the 90 patients, 28 were excluded during the six months follow-up 22 abstained, 3 were operated on the contra-lateral side, 3 suffered from other diseases that made it impossible to participate.
Thus the results of 62 patients mean age The process of selecting the items was due to the content validity, the dimensionality the construct validity and the responsiveness of the items and the new subscales. The selected items are presented in Table 1 and the items not selected in Table 2. The limit set to justify inclusion of an item into the HOOS was set to a mean relevance score of above 2.
One selected item, S10, difficulty spreading your legs, had a mean relevance score 1. All other selected items had a mean relevance score above 2.
The subscales indicating the most problems preoperatively were Sport and Recreation Function and Hip Related Quality of Life with mean scores of The subscale indicating the least problems preoperatively was Activities of Daily Living with a mean score of One patient reported best possible score ceiling effect preoperatively in the subscale Symptoms. The subscales indicating most problems at follow-up six months postoperatively were Sport and Recreation Function and Hip Related Quality of Life with mean scores of The subscale indicating the least problems at follow-up was Pain with a mean score of The highest correlations occurred between the SF subscales and the HOOS scales that are intended to measure similar constructs physical function vs.
Generally, higher correlations were seen when comparing HOOS scales to SF scales with a high ability to measure physical health, and lower correlations were seen when comparing HOOS scales to SF scales with a high ability to measure mental health, as shown in Table 4. Patients younger than 66 years of age reported higher responsiveness in all five subscales than patients older than 66 years of age Pain SRM 2. With improved general health and increased life span, expectations on physical activity and function by elderly are ever higher.
This raises the standard of outcome after THR. When measuring outcome after THR it is important to take into consideration the patient's expectations [ 19 ]. For active persons as well as for the more disabled, absence of pain is the most important reason for surgery.
Nevertheless, improved physical function is one of the main goals with the operation. In a previous study it was shown that younger patients obtain a better postoperative outcome than older, as assessed by WOMAC and SF [ 20 ]. This result was confirmed with the use of HOOS in the present study. We also found that Sport and Recreation Function and Hip Related Quality of Life were highly responsive for this group of patients with an average age of 73 years at surgery range 53—85 , with the responsiveness being highest for those younger than 66 years.
These dimensions are usually associated with a younger population but appear to be important also for the older. The time consuming process of developing a questionnaire could be shortened if already existing questionnaires could be adapted for use in similar patient groups. The present study, and previous studies [ 5 , 21 ], indicate that it is possible to adapt already existing outcome measures to obtain increased responsiveness.
A subgroup of patients in this study rated the relevance of each item included in the HOOS as shown in table 1. The additional questions dealt with walking on hard and uneven ground as well as spreading the legs. These problems were important for patients with hip dysfunction.
This is in contrast to two of the questions from KOOS table 2 which dealt with swelling and if the hip would catch or hang up when moving. These questions appear to be knee-related questions. Factor analysis can be used to check that each item has been attributed to the right scale [ 22 ]. When analysis was performed on all 51 items it was obvious that some of the items in each subscale loaded on another factor. That was the reason why P2, S8 and Q5 table 2 were not selected though they were relevant and had a sufficient responsiveness.
If an item loads on more than one factor it is difficult to know whether you measure what you intend to measure or not. Weakness, for example, S8 can definitely be a problem for patients with hip dysfunction but the reason for the problem may be of another cause than OA. When the selected 40 items were analyzed, all items loaded on a major factor for each subscale data not shown.
It is generally accepted that convergent construct validity is demonstrated if the correlations between scores on the same health component, as measured by two different instruments, is positive and appreciably above zero [ 23 ]. Mc Dowell and Newell [ 24 ] have noted in a review of rating scales and questionnaires that correlations for convergent construct validity often fall between 0. Consequently, the instrument used for comparison must be well validated. This may be due to the relatively low sensitivity for change over time for the two questions dealing with stiffness.
However, these questions seemed to be relevant for the patients. Responsiveness to clinical change is an important characteristic of outcome measures. High responsiveness indicates that fewer subjects are needed to demonstrate a significant difference [ 3.
Hip replacement is above all surgery for relieving pain and improving physical function [ 28 ]. The difference in responsiveness between the younger and older group of patients was less for the subscale Pain than the subscale Activity of Daily Living. This finding is in concordance with a previous study where the age of the patient seemed to be more important for improvement postoperatively for physical function than for pain [ 20 ].
In other words, pain is the most serious problem in this group of patients independent of age. Nevertheless, there is a great improvement concerning Sport and Recreation Function as well as Hip Related Quality of Life Figure 1 , most pronounced in the younger group of patients Table 5.
It is noteworthy that these dimensions that are associated with young patients are important also in this comparatively old group of patients. The follow-up time in the present study was limited to 6 months. It is known from a previous study [ 20 ] that pain relief is experienced very soon after surgery, while adaptation to the new health status takes at least 1 year.
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