J. Thometz, Xue C. Liu, Robert Rizza
Abstract
Introduction: A growth modulation device (GMD) was developed to explore the hypothesis: higher compressive forces induced by the GMD between intervertebral regions lead to changes of vertebral endochondral ossification.
Objectives: This study was to evaluate morphological changes of the spine within and adjacent to the instrumented segments, including the radiographic review, and histological analysis and to analyze growth rate and pattern of the asymmetric spine following the GMD as a function of time.
Materials and Methods: The four skeletally immature goats were approached via a standard thoracotomy from T6 to T10. The right side of the spine was exposed and instrumented with the GMD. One goat was sacrificed at 1, 2, 3, and 6 months following spinal surgery, respectively. Radiographs and histomorphometry were performed.
Results: The average Cobb angle (T2-T12) increased from 3° to 10°. The length (T6-T10) increased from 8.9cm to 12.6cm. Bony and cartilage density was greater on the instrumented side. The heights of physis were reduced (20%–33%) on the anterior of the instrumented side, but less on the posterior (12%–21%). Growth spurts are greatly reduced within the instrumented segments and growth remains constant over the animal's life, but on the vertebrae far from the instrumentation, growth is less affected, increases linearly, and the growth rate is higher.
Conclusion and Significance: The GMD yields an appreciable and controllable impact on the bony and cartilage density, and endochondral ossification height.