The application of arthroscopy to the hip and the development of magnetic resonance imaging (MRI) with contrast of the hip during the past decade have provided the orthopedic surgeon with the opportunity to treat a previously underserved subset of patients. Previously, young patients with hip pain and normal radiographs were treated with nonsteroidal anti-inflamatory drugs, physical therapy, and, occasionally, a cortisone injection. Patients in whom these modalities failed often were told that nothing was wrong, but were left with activity-limiting hip discomfort.
Today's hip arthroscopist has the opportunity not only to diagnose the source of pain for these patients using advanced MRI technology, but also to successfully treat these people at the time of arthroscopy. The development of this technology has created a need for a way to measure outcomes after conservative therapy and operative intervention. A measuring tool is needed to document outcomes, facilitate communication between physicians, and, most important, to allow the treating physician to give the patient an accurate prognosis.
The existing instruments for measurement of outcomes pertaining to the nonarthritic hip are not specific or concise enough for application to young and active patients. The nonarthritic hip score is short and easy to understand, to maximize compliance. The questionnaire takes approximately 5 minutes to complete, consisting of only 20 multiple-choice questions, all with the same five potential answers. It is self-administered, and all of the questions are equally weighted, therefore reducing the bias that can be introduced by the health care team. Finally, the nonarthritic hip score is similar to the Western Ontario and McMaster Universities Osteoarthritis Index, so the instrument is easily reproducible, internally consistent, valid, and responsive to clinical change.
Reproducibility reflects the ability of the measuring tool to give the same result when the test is given at different times, assuming no clinical change between test administrations. The high level of reproducibility in this study would likely have been higher if a shorter interval had been used between test administrations than the mean of 5.5 days in this study, be cause some patients may actually have experienced a true clinical change (a reduction in pain) between tests. However, with shorter intervals between tests, there is an increasing risk that reproducibility may be elevated falsely, because the patient may actually recall the answers given during the initial test administration.
The lowest Pearson correlation coefficient for any question was 0.63 for the third question in the pain subset, which queries the amount of pain that the patient is having at night while in bed. This question is similar to one on the Western Ontario and McMaster Universities Osteoarthritis Index, differing only in that it refers specifically to hip pain. The next lowest value was 0.72 for the second question in the mechanical symptom section.
Internal consistency reflects the ability of a series of questions to measure a similar, consistent concept, and it is measured using the Cronbach alpha. This study had good internal consistency within the questions comprising the mechanical symptom section, and excellent internal consistency within the items in each of the other three subsets. After re-examining the data and the questionnaire, it was not surprising that the internal consistency of the questions in the mechanical symptoms subset was not as great as that of the other subsets. This section asks four fairly different questions reflecting the most frequent complaints reported by this patient population. It is possible that a patient with a labral tear could have severe locking or catching in the hip, but also have normal motion and little or no stiffness in the hip. Likewise, it is possible for a patient with synovitis to have stiffness and reduced motion without any catching or locking. Although these questions are not completely consistent and interrelated, they are necessary to completely evaluate this patient population. Furthermore, the questions in this section are somewhat related, and a low score in this section reflects intense symptomatology.
Validity refers to whether the instrument is actually assessing what it is intended to measure. The high Pearson correlation coefficient of 0.82 between the nonarthritic and the Harris hip scores shows that both scores measure similar characteristics. This close relationship validates the nonarthritic hip score using the American gold standard in hip assessment. Despite the similarities between the two scores, these two outcome measures are structured quite differently, and the questions are directed at very different populations.
The Pearson correlation coefficient between the Harris hip score and each subset of the nonarthritic hip score was 0.73 for pain, 0.61 for mechanical symptoms, 0.73 for physical function, and 0.76 for ability to participate in varying levels of activity. The high correlation between the pain subset and the Harris hip score was expected, since the latter allocates 44 points out of 100 possible points (44%) to one question regarding pain. The lowest correlation exists between the mechanical symptoms subset and the Harris hip score, because the latter does not ask questions pertaining to the hip catching, locking, or giving way.
The correlation of the nonarthritic hip score with the Short Form-12 was similar to the correlation of the Harris hip score with the Short Form-12. The coefficients were 0.59 and 0.63, respectively. This level of correlation was expected, because the nonarthritic and Harris hip scores measure hip function and the Short Form-12 measures global wellness. The correlation of the nonarthritic hip score and the physical and emotional portions of the Short Form-12 were 0.37 and 0.51, respectively. Greater congruency with the physical portion of the Short Form-12 would have been expected, because the questionnaire does not have any questions regarding feelings and emotions. The authors concluded that the relatively low correlation results from the fact that the physical portion of the Short Form-12 does not ask any questions pertaining specifically to the hip. Moreover, these patients often are frustrated and scared after having seen multiple physicians without significant improvement. This may explain the modest correlation between the nonarthritic hip score and the emotional portion of the Short Form-12.
Responsiveness to clinical change of the nonarthritic hip score is being studied and compared with the Harris hip score and the Short Form-12. Patients are being assessed before hip arthroscopy and again 6 months postoperatively. In addition to completing the three scores preoperatively and 6 months after surgery, the patients also must complete a short patient-satisfaction questionnaire postoperatively to help determine which score is the most sensitive to change. Once there is an instrument that is reliable, valid, and sensitive to clinical change, it will be possible to understand which diagnoses respond best to hip arthroscopy.
This short, self-administered questionnaire evaluating hip pain in young patients with increased activity demands and high treatment expectations is reproducible, internally consistent, and valid compared with previous measures of hip performance. This measurement device can be used to assess patients with nonarthritic hip pain both before intervention and after treatment. In addition, it can be used to record outcomes and facilitate communication between physicians who treat this challenging group of patients.
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