Bone density in myelomeningocele: the effects of ambulatory status and other factors

Measurements were made of distal radius, mid-radius, tibia and metatarsal bone-density of 80 patients with myelomeningocele (17 thoracic, six L1/L2, 13 L3, 30 L4, 14 L5/sacral). For the upper extremity the bone density primarily was low in the thoracic patients, but in the tibia and metatarsal it showed a more linear correlation with neurological levels. The effect of age was highly significant at all sites; after controlling for this, the neurological level was a significant determinant of bone density at all sites, and this effect was greater in older children. Patients with impaired ambulation had decreased bone-density in the distal radius, tibia and metatarsal, but not in the mid-radius. Race had no significant effect on density after accounting for differences in neurological level. Weight for height and multiple fractures did not correlate with bone density. Although ambulatory status (weight-bearing stresses) and neurological status (muscle stresses) are both important factors in bone density, this study suggests that the latter is a more important determinant.