Abstract
BACKGROUND: The use of portable hand-held dynamometers is increasing in popularity due to their ease of use in different clinical settings, convenient size, portability, and overall affordability. Reported reliability for external fixation and rater-stabilized hand-held dynamometry (HHD) strength measurements have been found to be 'good' to 'excellent'. Inconsistent agreement has been found between the two stabilization methods and isokinetic HHD testing. PURPOSE / HYPOTHESIS: Determine the reliability and agreement of HHD measurements in three different rater test positions against three different mechanically produced force magnitudes. The study compared measurements obtained by rater-stabilization to external fixation methods. STUDY DESIGN: Intra-rater and inter-rater reliability study. METHODS: Ten raters took measurements in three different rater test positions against three different force magnitudes created by an external force. Raters were blinded to the randomized force magnitudes. The rater's measurements were compared to measurements taken against an external fixation stabilization device. To establish reliability, Intraclass Correlation Coefficient (ICC), and Standard Error of Measurement (SEM), and Minimal Detectable Change (MDC) were used. To establish agreement, error rates between the rater-stabilized and external fixation stabilization measurements were calculated. RESULTS: ICC's were found to be 'excellent' at .97 and above. The relative SEM ranged from 0.2% to 0.9 % and the relative MDC ranged from 0.7% to 2.8%. The overall error rate was 15.5% and was influenced by force magnitude. CONCLUSION: The use of standardized rater test positions resulted in 'excellent' intra-rater, inter-rater reliability, low SEM, and low MDC for rater-stabilized HHD measurements. A systematic error was observed, with rater-stabilized measurements resulting in higher values compared with values obtained with the external fixation method. LEVEL OF EVIDENCE: 3.