Test-Retest Reliability of Isokinetic Dynamometry for the Assessment of Spasticity of the Knee Flexors and Knee Extensors in Children With Cerebral Palsy

Pierce SR, Lauer RT, Shewokis PA, Rubertone JA, Orlin MN. Test-retest reliability of isokinetic dynamometry for the assessment of spasticity of the knee flexors and knee extensors in children with cerebral palsy.ObjectiveTo assess test-retest reliability of the peak resistance torque and slope of work methods of spasticity measurement of the knee flexors and extensors in children with cerebral palsy (CP).DesignTest-retest reliability study.SettingPediatric orthopedic hospital.ParticipantsFifteen children with CP.InterventionKnee extensor and flexor spasticity was assessed with an isokinetic dynamometer using passive movements at 15°, 90°, and 180°/s taken 1 hour apart.Main Outcome MeasuresPeak resistive torque and work were calculated. The relative and absolute test-retest reliability was calculated by using intraclass correlation coefficients (ICCs) and Bland-Altman plots, respectively.ResultsRelative reliability was good (ICC>.75) for slope-of-work and peak resistance torque measurements at a velocity of 180°/s, whereas reliability of peak torque measurements was decreased (ICC<.51) at slower velocities for both muscle groups. The 95% limits of agreement of Bland-Altman plots contained most data points for both methods, but the width of the limits of agreement were wide.ConclusionsThe measurement of spasticity of the knee extensors and flexors in children with CP using peak-resistance torque at 180°/s and the slope of work method has acceptable relative test-retest reliability. However, the absolute reliability of spasticity data should be considered cautiously.