Inter-observer reproducibility of measurements of range of motion in patients with shoulder pain using a digital inclinometer
1 Institute for Research in Extramural Medicine, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, the Netherlands
2 Department of Social Psychiatry, University of Groningen, P.O. Box 30001, 9700 RB Groningen, the Netherlands
3 Dutch National Institute for Allied Health Professions, P.O. Box 1161, 3800 BD Amersfoort, the Netherlands
4 TNO Work and Employment, P.O. Box 718, 2130 AS Hoofddorp, the Netherlands
5 Netherlands Institute for Health Services Research (NIVEL), P.O. Box 1568, 3500 BN Utrecht, the Netherlands
6 Department of Rheumatology, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, the Netherlands
7 Dutch Cochrane Centre, J2-229, Academic Medical Center, P.O. Box 22660, 1100 DD Amsterdam, the Netherlands
BMC Musculoskeletal Disorders 2004, 5:18 doi:10.1186/1471-2474-5-18Published: 14 June 2004
Reproducible measurements of the range of motion are an important prerequisite for the interpretation of study results. The digital inclinometer is considered to be a useful instrument because it is inexpensive and easy to use. No previous study assessed inter-observer reproducibility of range of motion measurements with a digital inclinometer by physical therapists in a large sample of patients.
Two physical therapists independently measured the passive range of motion of the glenohumeral abduction and the external rotation in 155 patients with shoulder pain. Agreement was quantified by calculation of the mean differences between the observers and the standard deviation (SD) of this difference and the limits of agreement, defined as the mean difference ± 1.96*SD of this difference. Reliability was quantified by means of the intraclass correlation coefficient (ICC).
The limits of agreement were 0.8 ± 19.6 for glenohumeral abduction and -4.6 ± 18.8 for external rotation (affected side) and quite similar for the contralateral side and the differences between sides. The percentage agreement within 10° for these measurements were 72% and 70% respectively. The ICC ranged from 0.28 to 0.90 (0.83 and 0.90 for the affected side).
The inter-observer agreement was found to be poor. If individual patients are assessed by two different observers, differences in range of motion of less than 20–25 degrees can not be distuinguished from measurement error. In contrast, acceptable reliability was found for the inclinometric measurements of the affected side and the differences between the sides, indicating that the inclimeter can be used in studies in which groups are compared.