Novel Hemi-staple for the Fusionless Correction of Pediatric Scoliosis: Influence on Intervertebral Discs and Growth Plates in a Porcine Model.

STUDY DESIGN: In vivo porcine model utilized to evaluate the influence of an intravertebral fusionless growth modulating device (hemi-staple) on intervertebral discs and growth plates.

OBJECTIVE: Evaluate radiographic and histological changes in discs and growth plates with the purpose of measuring influence of the explored hemi-staple.

SUMMARY OF BACKGROUND DATA: Fusionless growth modulation for the early treatment of scoliosis should insure the long term viability of the intervertebral disc and successfully reduce or arrest local growth. A novel hemi-staple that proved effective control of coronal spinal alignment warranted further analyses of its influence on the disc health and growth plate morphology.

METHODS: A hemi-staple that inhibited local vertebral growth exclusive of the disc was introduced over T5-T8 in 4 immature pigs (16 vertebrae) (experimental) while 3 underwent surgery without instrumentation (sham) and 2 had no intervention (control). Three month follow up prior to animal euthanasia provided radiographic (disc height and health) and histological (growth plate morphology, disc health, and type X collagen distribution) analyses.

RESULTS: No post-operative complications were experienced. Radiographic data returned inverse disc wedging (greater disc height adjacent to device, 2.6 mm ±0.7 compared to the non-instrumented side, 1.8 mm ±0.5) in experimental segments and suggested disc viability. Histological data confirmed device growth modulation through significant local reduction of growth plate hypertrophic zone (125.64 μm ±16.61 and 61.16 μm ±8.25 in non-instrumented and instrumented sections, respectively) and cell height (16.14 μm ±1.87 and 9.22 μm ±1.57 in non-instrumented and instrumented sections, respectively). A variability of disc health, dependant of device insertion location, was observed. Type X collagen was consistently identified in experimental growth plates and absent from intervertebral discs.

CONCLUSIONS: Hemi-staples decreased growth plate hypertrophic zone and cell height, and, depending on device insertion site, showed positive signs of disc health sustainability. Spinal growth modulation achieved exclusive of disc compression, as practiced by this method, offers unique advantages over other fusionless techniques. This technique may provide a suitable and attractive alternative for the early treatment of idiopathic scoliosis.