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Spine (Phila Pa 1976). 1996 May 15;21(10):1162-7.

Mechanical modulation of vertebral body growth. Implications for scoliosis progression.

Author information

1
Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington, USA.

Abstract

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.

PMID:
8727190
[Indexed for MEDLINE]

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