Hip disability : patient education, classification and assessment

Abstract

Hip disability is common and entails activity limitations, participation restrictions and increased risk of further disability and health problems, partially due to inactivity. Hip osteoarthritis (OA), the major diagnosis, is difficult to define, especially when no joint space narrowing is seen in radiography. However, radiological hip OA can be asymptomatic. The American College of Rheumatology (ACR) has developed clinical classification criteria for symptomatic hip OA, including two range-of-motion (ROM) variables: flexion and internal rotation. It has been clinically accepted that hip OA, with joint capsule involvement, occasions a "capsular pattern" of decreased ROM, but the exact ordering of the directions is controversial. Patient education in groups is an important supplement to individual treatment and is recommended by the ACR and the European League of Associations of Rheumatology for patients with OA.

The overall objective of the present thesis was to develop early educational treatment in primary care for people with hip disability - a Hip School - and to assess its effects on self-rated hip problems and health-related quality of life. Further objectives were to analyse common diagnostic and classification criteria and to improve instruments for assessing self-rated hip problems.

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), available in both knee and hip formats, was translated into Swedish and tested. A Hip School led by physiotherapists was developed covering, among other things, self-help hints (e.g. advice about daily physical activity to appropriate extents for at least a total of 30 minutes, hip ROM training at the end point of motion, and not sitting for longer than 20 minutes at a time). For assessment of the Hip School, persons with hip disability were recruited to a treatment group (n = 77) or to a control group (n = 68). Self-rated hip problems were assessed with the WOMAC and health-related quality of life with the Nottingham Health Profile (NHP) before and 6 months after the Hip School. The treatment group was also tested after an additional 6 months. For 168 persons with hip disability, passive range of motion (PROM) was tested in six directions with a goniometer. PROM limitations were calculated with three different norms and arranged by size in PROM patterns. The patterns and the number of hips with patterns corresponding to proposed capsular patterns were counted. Fifty-two persons with hip disability answered an extended version of the WOMAC twice with a one-week interval. Reproducibility, percentage of zero scores (best possible score) and mean scores of symptoms and perceived importance were analysed.

The results showed that the Swedish version of WOMAC is a reliable, valid, and responsive instrument with measurement qualities in agreement with the original version. Assessment of the Hip School showed that the participants reduced their pain and activity limitations and improved their health-related quality of life after 6 months with maintained effects after one year. It was not possible to predict radiological evidence of hip OA from the multitude of PROM patterns. No support was found for the existence of a hip joint "capsular pattern". The failure of the clinical signs to coincide satisfactorily with radiographic hip OA was further emphasised when the ACR clinical classification criteria were used, as they achieved a sensitivity of 85% and a specificity of 25%. Gender and other factors such as age, ROM exercise and other ROM-demanding habits influence PROM. Being male contributed almost as much as having hip OA to the risk of having decreased hip ROM. The extended instrument Hip disability and osteoarthritis outcome score (HOOS), appears to be evaluative with increased ability, especially in early-stage hip disability, to detect clinically important change over time.

It is concluded that the Hip School can be a useful early treatment strategy for persons with hip disability. It is not possible to diagnose hip OA with "capsular patterns" or to classify hip OA in early cases from reduction in PROM directions. HOOS can be used to assess treatment strategies.