Long-term effects of strokes on bone mass

The purpose of the study was to determine the long-term effects of muscle weakness secondary to strokes on the bone mineral content of the hemiparetic limb. Patients who had experienced single recent strokes were studied. The bone mineral content of each limb was measured by Dual Energy X-ray Absorptiometry using the region of interest analysis program. Muscle strength of each muscle group was ranked using the Oxford scale, and the mean was calculated for each limb. Bone and muscle parameters were measured within seven days after the stroke and repeated thereafter at monthly intervals for up to 6 mo. A repeated measures analysis of variance, Newman-Keuls pair-wise comparisons, and orthogonal contrasts were done for each parameter. Significance levels were set at P < 0.05. Sixteen patients were included in this study. Demineralization was more pronounced in the upper than lower limbs. Demineralization of bones on the paralyzed side started during the first month after the stroke and gradually progressed. By the fourth month, the bone mineral content decreased by a mean of 9.3% (P = 0.01) and 3.7% (P = 0.01) in the upper and lower limbs, respectively, for the 11 patients followed for 4 mo. In the patients we followed for more than 4 mo, there was no further significant mineral loss. No change in bone mineral content was observed in the healthy nonparetic limbs. In conclusion, after a stroke, bone demineralization occurs in the paralyzed side and reaches its maximum within 3 to 4 mo. Arms are affected more than legs.