Longitudinal assessment of grip strength using bulb dynamometer in Duchenne Muscular Dystrophy

BACKGROUND:

Grip strength is used to infer functional status in several pathologicalconditions, and the hand dynamometer has been used to estimate performance inother areas. However, this relationship is controversial in neuromuscular diseasesand studies with the bulb dynamometer comparing healthy children and children withDuchenne Muscular Dystrophy (DMD) are limited.

OBJECTIVE:

The evolution of grip strength and the magnitude of weakness were examined in boyswith DMD compared to healthy boys. The functional data of the DMD boys werecorrelated with grip strength.

METHOD:

Grip strength was recorded in 18 ambulant boys with DMD (Duchenne Group, DG) aged4 to 13 years (mean 7.4±2.1) and 150 healthy volunteers (Control Group, CG)age-matched using a bulb dynamometer (North Coast- NC70154). The follow-up of theDG was 6 to 33 months (3-12 sessions), and functional performance was verifiedusing the Vignos scale.

RESULTS:

There was no difference between grip strength obtained by the dominant andnon-dominant side for both groups. Grip strength increased in the CG withchronological age while the DG remained stable or decreased. The comparisonbetween groups showed significant difference in grip strength, with CG valueshigher than DG values (confidence interval of 95%). In summary, there was anincrement in the differences between the groups with increasing age. Participantswith 24 months or more of follow-up showed a progression of weakness as well asmaintained Vignos scores.

CONCLUSIONS:

The amplitude of weakness increased with age in the DG. The bulb dynamometerdetected the progression of muscular weakness. Functional performance remainedvirtually unchanged in spite of the increase in weakness.