Enhanced left-finger deftness following dominant upper-and lower-limb amputation

Background. After amputation, the sensorimotor cortex reorganizes, and these alterations might influence motor functions of the remaining extremities. Objective. The authors examined how amputation of the dominant or nondominant upper or lower extremity alters deftness in the intact limbs. Methods. The participants were 32 unilateral upper-or lower-extremity amputees and 6 controls. Upper-extremity deftness was tested by coin rotation (finger deftness) and pegboard (arm, hand, and finger deftness) tasks. Results. Following right-upper-or right-lower-extremity amputation, the left hand's finger movements were defter than the left-hand fingers of controls. In contrast, with left-upper-or left-lower-extremity amputation, the right hand's finger performance was the same as that of the controls. Conclusions. Although this improvement might be related to increased use (practice), the finding that right-lower-extremity amputation also improved the left hand's finger deftness suggests an alternative mechanism. Perhaps in right-handed persons the left motor cortex inhibits the right side of the body more than the right motor cortex inhibits the left side, and the physiological changes induced by right-sided amputation reduced this inhibition.