Three-dimensional analysis of 2 fusionless scoliosis treatments: a flexible ligament tether versus a rigid-shape memory alloy staple.

Study Design: Experimental scoliosis was created and subsequently corrected in goats. The 3-dimensional (3-D) effects of the treatments were analyzed.
Objective: To analyze the 3-D effect of 2 different fusionless scoliosis treatment techniques on an experimental idiopathic-type scoliosis using plain radiographs and computerized tomography.
Summary of Background Data: Scoliosis is a complex 3-D spinal deformity with limited treatment options. By preserving growth, motion, and function of the spine, fusionless scoliosis surgery provides theoretical advantages over current forms of treatment.
Methods: Scoliosis was created in 24 Spanish cross-X female goats using a flexible, left posterior asymmetric tether from the T5 to L1 laminae, with convex rib resection and concave rib tethering from T8 to T13. After 8 weeks of posterior tethering, goats were randomized into 3 treatment groups: group 1, no treatment; group 2, anterior-shape memory alloy staple; and group 3, anterior ligament tether with bone anchor. The 6 levels of maximal curvature were instrumented in groups 2 and 3. All goats were observed for an additional 12-16 weeks. Serial radiographs and computerized tomography were used to document progression/correction of coronal, sagittal, and transverse plane deformities throughout the study.
Results: There were 20 goats that had progressive, structural, idiopathic-type, lordoscoliotic curves convex to the right in the thoracic spine over the 8-week tethering period. An overall deformity score equaling the sum of the scoliosis, lordosis, and axial rotation measurements was calculated for each goat at 3 times.
Conclusion: The data in this study show the ability of a ligament tether attached to a bone anchor to correct scoliosis modestly in the coronal plane, but not in the sagittal or transverse plane. In addition, although a significant decrease in the deformity score was shown initially in this group (P < 0.001), the effect was lost over time. The final deformity in the bone anchor/ligament tether group wassignificantly less than either the stapled or untreated groups (P < 0.03). Further study is warranted to provide a better understanding of the 3-D effects of fusionless scoliosis treatments.