Reliability of a new hand-held dynamometer in measuring shoulder range of motion and strength

Abstract

Acceptable reliability is a prerequisite for inclusion of physical examination tests in clinical examinations of the painful shoulder. The aim of this study was to establish the intraexaminer and interexaminer reliability of measures of shoulder range of motion (ROM) and muscle force using a new hand-held dynamometer with the ability to standardize overpressure force during passive ROM tests. Forty consecutive subjects with shoulder pain were recruited, and tests were performed by two physiotherapists. Tests included active ROM elevation, passive ROM glenohumeral abduction and external rotation and resisted abduction and external rotation. All tests demonstrated high levels of intraexaminer reliability (ICC 0.85–0.99; LOA 6–24° and 1.1–7.0 kg). Highest levels of interexaminer reliability reliability were observed for measures of active ROM flexion (ICC 0.88–0.95; LOA 14–22°). Passive ROM tests demonstrated ’moderate – substantial’ interexaminer reliability (ICC 0.45–0.62; LOA 25–34°). The ICCs for resisted tests ranged from 0.68 to 0.84, and LOA ranged from 3.2 to 8.5 kg. Active ROM flexion demonstrated high levels of both intra- and interexaminer reliability. Measures of passive ROM and peak isometric force demonstrated acceptable levels of intraexaminer reliability.

Introduction

Shoulder pain is a common complaint resulting in significant pain, functional disability and loss of quality of life (Turner-Bowker et al., 2003, MacDermid et al., 2004, Lin et al., 2005). The diagnosis of shoulder pain involves a clinical examination which typically consists of a variety of physical examination tests and associated measures including active and passive range of motion (ROM), and resisted muscle tests. The results of these tests including measures of active shoulder elevation and passive ROM abduction and external rotation are commonly used for diagnostic classification, and in the assessment of functional impairment (Constant and Murley, 1987, Davis, 1998, Harrington et al., 1998, MacDermid et al., 2007). Reliable measurements are required if these classifications are to be consistently applied.

Although few studies have directly compared reliability between active and passive ROM of the shoulder, more variability has been reported in measures of passive ROM (ICC 0.26–0.90) versus active ROM (ICC 0.49–0.88) (Riddle et al., 1987, Hayes et al., 2001, Hoving et al., 2002, Terwee et al., 2005). A common explanation for this variability in measures of passive ROM is the inability of the examiner to standardize the amount of overpressure applied at the end range of motion (Boone et al., 1978, Gajdosik and Bohannon, 1987, Lea and Gerhardt, 1995, Hayes et al., 2001). A new hand-held dynamometer (HHD) (Industrial Research Ltd) has been developed that has the ability to simultaneously measure both angle and force. This feature enables the standardization of overpressure force at end range of motion. Whether this feature would reduce measurement variability and improve reliability during measures of passive ROM has not been tested to date.

Measures of muscle strength are used in the diagnostic process to assess muscle integrity and to determine the level of any strength deficits (Constant and Murley, 1987, Cyriax, 1982). Hand-held dynamometry has demonstrated higher sensitivity, and interexaminer reliability than manual muscle testing in identifying strength deficits of the rotator cuff (Ellenbecker, 1996, Leggin et al., 1996, Hayes et al., 2002, Tyler et al., 2005). Hand-held dynamometry therefore provides an advantage over manual muscle testing for the accurate clinical assessment of isometric muscle strength. The reliability of the new HHD needs to be established for measurements of muscle strength before it can be used for this purpose in the clinical setting.

Thus, the aim of this study was to establish the intra- and interexaminer reliability of a new HHD in measuring ROM and isometric muscle strength of the symptomatic shoulder. Whether reliability of measures of passive ROM could be improved by standardizing the amount of overpressure force applied at end range of motion was specifically investigated.