Strength testing using hand-held dynamometry of hip flexor, extensor and abductor muscles following hip resurfacing arthroplasty: an investigation of inter-rater reliability.
Newman MA, Duffy KRB, Sheehan J, Reilly K, Barker KL.
Physiotherapy Research Unit, Nuffield Orthopaedic Centre NHS Trust, Windmill RD, Oxford, OX37LD. Tel: 01865 737526 Fax: 01865 738043
Purpose To assess inter-rater reliability of muscle strength measures obtained with a hand held dynamometer (HHD) following hip resurfacing arthroplasty (HRSA). Relevance Reliable strength assessment after HRSA is essential to quantify impairments, plan rehabilitation and assess outcomes [1]. Manual testing has limitations; HHD is an alternative with reliability established for varied conditions [2]. However reliability is linked to the population studied and the reliability of HHD is unknown in this population. Subjects Twenty four people attending a review following HRSA participated; 8 women and 16 men mean age 57 (SD 7.6), 11 right, 13 left. Methods Three measures of hip flexor, abductor and extensor strength were made using a Lafayette HHD by 2 physiotherapists independently 15 minutes apart on one occasion. A standard protocol was used that incorporated a ‘make’ test, positioning, instructions and dynamometer placement. Analysis Data was analysed using both intra-class correlation coefficients (ICCs) and Bland and Altman plots. The first and mean of the 3 measures were compared. Results All ICCs were above 0.75 suggesting good reliability [3]. ICCs of mean measures were higher than first measures: flexors 0.86 (CI: 0.69-0.94), abductors 0.93 (CI: 0.85 -0.97) and extensors 0.90 (CI: 0.77-0.96). Average bias in measures was small: mean difference flexors -1.4, abductors -0.8, extensors-1.9 but 95% limits of agreement suggested moderate variability, particularly for hip flexors. Conclusion HHD appeared a reliable method of assessing hip strength after HRSA. Using the mean of 3 measures, a make test and standard protocol to reduce random error is recommended.
References
1. Newman MA, Barker KL, Pandit H, Murray DW. Outcomes after metal–on–metal hip resurfacing: Could we achieve better function? Archives of Physical Medicine and Rehabilitation 2008; 89:660–9. 2. Kolber MJ, Cleland JA. Strength testing using hand held dynamometry. Physical Therapy Reviews 2005; 10: 99–112. 3. Sim J, Wright C. Research in Health Care: Concepts, designs and methods. 2000; Nelson Thornes, Cheltenham.