Metacarpal squeezing reduces grip strength

Unduly tight plaster hand casts may narrow the metacarpal joint space, hindering rehabilitation. This study investigated how metacarpal narrowing affects grip strength. Forty-two adult volunteers with no other pathology were included. Dominant and non-dominant hand grip strength was measured with a digital hand dynamometer (Jamar plus, China). Metacarpal width was measured with a metal caliper, and the caliper was then fixed at 10% narrowing of the joint space, and a second measurement of grip strength was taken. The measurements were thus taken twice each in the dominant and non-dominant hand, and the average of the two was recorded. A total 336 measurements were taken in the dominant and non-dominant hands of 42 individuals at two time points. There was no significant difference in grip strength between dominant and non-dominant hands (p = 0.183). After 10% narrowing, both the dominant and the non-dominant hand showed a mean 33.4% reduction in grip strength: i.e., squeezing the metacarpus with a caliper significantly reduced grip strength in both dominant and non-dominant hands (p = 0.01). The study thus showed that grip strength will decrease significantly when the metacarpus is squeezed by a tight cast. Although the patient does not feel the 10% narrowing of the metacarpus, it is clear that hand muscle mass may be adversely affected in the long term.