Lumbar Scoliosis Induction in Juvenile Dogs by Three-dimensional Modulation of Spinal Growth Using Nickel-Titanium Coil Springs

BACKGROUND Current treatments for scoliosis have some defects and complications. To study spinal deformities and test novel scoliosis treatments, many animal models of scoliosis have been developed. These models applied a single load to the spine and could not precisely modulate the spinal growth in different dimensions. In this study, we applied posterior tethering in various directions with the application of nickel-titanium (NT) coil springs in dog's spine to modulate spinal growth in the coronal, sagittal, and transverse planes and create a scoliosis model possess curves that mimic adolescent idiopathic scoliosis (AIS) three dimensionally. METHODS Scoliosis was surgically induced in eight 8-week-old female dogs (weight: 1.95-2.30 kg) using bone screws and NT coil springs. The deformity was induced through the placement of posterior NT coil springs that tethered the spine by bone screw fixation. All dogs were monitored with serial radiographs to document changes in deformities. RESULTS All experimental animals developed scoliotic curves convex to the left in the lumbar segment. The mean coronal Cobb angle was 18.0° immediately postoperatively and 54.5° at 22 weeks. The mean lordosis increased from 6.2° postoperatively to 35.0° at final follow-up. Apical axial rotation increased from 4.5° postoperatively to 31.2° at 22 weeks. CONCLUSIONS With the application of NT springs in dogs that allowed posterior tethering in various directions, lumbar spinal deformity was achieved in three planes: coronal, sagittal, and transverse planes. Notably, the lumbar spine in surgically treated dogs developed lordoscoliosis with obvious rotation and the curves mimic AIS three dimensionally well. This method allows lumbar scoliosis to develop without deep dissection of muscle and maintains the essential anatomical elements along the spinal curve. Moreover, the spinal growth modulation technique could yield information that would provide a basis for developing novel early-stage treatments for children with scoliosis.