A new clinical device for measuring wrist strength in people with tetraplegia

Weakness of wrist muscles has a significant impact on upper limb function in people with tetraplegia. A simple device has been designed to enable clinicians to measure dynamic strength in the very weak muscles of people with tetraplegia. The objective of this study was to test the interrater reliability of the device. Twenty wrists of 12 people with tetraplegia and associated wrist extensor weakness (grade 2-4) were included in the study. The strength of the wrist extensor muscles was measured by blinded assessors on two separate occasions 1-3 days apart. Measurements were conducted in a device that ensured the resistive torque was constant as the wrist moved through full range of motion. Intraclass correlation coefficients and percent close agreement scores were used to measure reliability. The intraclass correlation coefficient was 0.88 (95% CI 0.72-0.95). Repeat measurements of wrist extensor torque were within 0.5 Nm 75% of the time and 0.7 Nm 90% of the time. This device is a simple and reliable way of measuring dynamic wrist extensor strength of people with tetraplegia. It is appropriate for use in the clinical setting.