The validity of button fastening as a test of hand disability in myotonic dystrophy.

This study evaluated the validity of testing button fastening ability as a measurement of hand disability in patients with myotonic dystrophy. Forty subjects with myotonic dystrophy were tested on their ability to fasten four shirt buttons. The association between button fastening ability, strength of selected proximal upper limb muscles and lateral pinch grip was determined. A significant association (F(4,35) = 7.55, p < 0.01) was demonstrated between proximal upper limb strength and button fastening ability, but there was no relationship with lateral pinch grip strength. Myotonia was not a factor affecting button fastening performance. Comparison of these results with those of a group of 13 subjects with other neuromuscular diseases showed button fastening disability in myotonic dystrophy could not be attributed solely to proximal upper limb weakness but is a valid measure of hand disability. A standard for normal button fastening performance was also determined.