Reliability of maximum isometric arm, grip and pinch strength measurements in children (7–12 years) with unilateral spastic cerebral palsy

Abstract

Purpose: To investigate test–retest and inter-rater reliability of maximum isometric arm muscle strength measurements using the hand-held dynamometer (HDD) and maximum isometric grip and pinch strength measurements using the Biometrics E-Link Evaluation System in children aged 7–12 years with unilateral spastic cerebral palsy.

Materials and methods: All data were obtained using a test–retest study design. The study met the conditions of the COSMIN criteria to achieve good methodological quality.

Results: For arm strength measurements, all test–retest reliability intraclass correlation coefficient (ICC) values and all but one inter-rater reliability ICC value indicated excellent reliability. For grip- and pinch strength measurements, all test–retest reliability and inter-rater reliability ICC values showed excellent reliability. The standard error of measurement values ranged from 4.97 to 11.36 N (HDD) and 0.37 to 1.81 kg (E-link). Smallest detectable change values ranged from 13.79 to 31.49 N (HDD) and 1.03 to 5.02 kg (E-link).

Conclusions: The HDD and E-link system are usable measurement instruments for cross-sectional muscle strength measurements in children with unilateral spastic cerebral palsy. It is not clear if both instruments are usable to measure changes in muscle strength within an individual, especially if a child with unilateral spastic cerebral palsy has low muscle strength. Caution in the interpretation of changes in muscle strength is therefore necessary.

Implications for Rehabilitation

• The hand-held dynamometer and E-Link Evaluation System are reliable measurement instruments to measure muscle strength of the arm and hand in children with unilateral spastic cerebral palsy, aged 7–12 years.

• Cross-sectional measurements; it is possible to measure upper extremity muscle strength in children with unilateral spastic cerebral palsy with the hand-held dynamometer and E-link system.

• Longitudinal measurements; changes in upper extremity muscle strength within one person should be interpreted with care, especially if a child with unilateral spastic cerebral palsy has low muscle strength.

Keywords:

• Unilateral cerebral palsy
• muscle strength
• arm strength
• grip strength
• reliability
• clinimetric properties
• hemiplegia
• children

Acknowledgements

We thank all children and their parents who participated in this study. Also special thanks to the schools and/or rehabilitation centers that participated in this study and to Dr. Caroline Bastiaenen for assistance with the statistics and interpretation of results.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The study was funded by “Stichting Vooruit voor kinderen met een handicap”, “Stichting Innovatie Revant” and the “Johanna KinderFonds”. The funders had no role in the design, the data collection, analysis, and interpretation; the reporting of this work, or the decision to submit the work for publication.