Mechanical modulation of calf tail vertebral growth: Implications for scoliosis progression

The purpose of this study was to determine whether compression and distract ion applied to adjacent vertebrae in the calf tail could modulate vertebral growth. Seven 6-week-old calves had two pairs of adjacent tail vertebrae i nstrumented with an Ilizarov external fixator with calibrated springs desig ned to apply a 30-50-N axial load to the vertebrae. Data were obtained from 17 vertebrae loaded in compression and 4 vertebrae loaded in distraction. Vertebrae adjacent (cranial and caudal) to the instrumented vertebrae serve d as controls. The length of each vertebra on the postoperative radiograph was subtracted from the length of the same vertebra on the radiograph taken 6 months after the operation to calculate vertebral growth. The vertebrae loaded in compression had a growth rate of 68 +/- 42% of that of the contro ls. In contrast, the vertebrae loaded in distraction had a growth rate of 1 23 +/- 78% of that of the controls.