Mechanical modulation of vertebral body growth. Implications for scoliosis progression

Spine (Phila Pa 1976). 1996 May 15;21(10):1162-7. doi: 10.1097/00007632-199605150-00007.


Study design: The authors developed a rat-tail model to investigate the hypothesis that vertebral wedging during growth in progressive spinal deformities results from asymmetric loading in a "vicious cycle."

Objectives: To document growth curves with axial compression or distraction applied to tail vertebrae to determine whether compression load slows growth and distraction accelerates it.

Summary of background data: Progression of skeletal deformity during growth is believed to be governed by the Hueter-Volkmann law, but there is conflicting evidence to support this idea.

Methods: Twenty-eight 6-week-old Sprague-Dawley rats were assigned to one of three groups: compression loading, distraction loading, or sham (apparatus applied without loading). Under general anesthesia, two 0.7-mm diameter stainless steel percutaneous pins were used to transfix each of two vertebrae. The pins were glued to 25-mm diameter external ring fixators. Springs (load rate, 35 g/mm) were installed on three stainless steel threaded rods that were passed through holes in each ring and compressed with nuts to apply compression or distraction forces between 25-75% of bodyweight. Vertebral growth rates in microns/day were measured by digitizing the length of the vertebrae images in radiographs taken 0, 1, 3, 5, 7, and 9 weeks later.

Results: The loaded vertebrae grew at 68% of control rate for compressed vertebrae and at 114% for distracted vertebrae. (Differences statistically significant, P < 0.01 by analysis of variance.) For the compressed vertebrae, the pinned vertebrae, which were loaded at one of their two growth cartilages, grew at a reduced rate (85%), although this effect was not apparent for the distraction animals.

Conclusions: The findings confirm that vertebral growth is modulated by loading, according to the Hueter-Volkmann principle. The quantification of this relationship will permit more rational design of conservative treatment of spinal deformity during the adolescent growth spurt.

MeSH terms

  • Animals
  • Internal Fixators
  • Lumbar Vertebrae / growth & development*
  • Lumbar Vertebrae / physiology*
  • Lumbar Vertebrae / surgery
  • Rats
  • Rats, Sprague-Dawley
  • Scoliosis / physiopathology*
  • Tail / growth & development
  • Tail / physiology
  • Tail / surgery
  • Weight-Bearing / physiology