Fusionless scoliosis correction using a shape memory alloy staple in the anterior thoracic spine of the immature goat

Study Design. Experimental scoliosis was created in goats and then treated using anterior thoracic stapling. Objective. To correct, without fusion, a progressive idiopathic-type scoliotic deformity in an immature goat model using a shape memory alloy staple. Summary of Background Data. Fusionless scoliosis treatment techniques, using minimally invasive approaches to the anterior thoracic spine, provide theoretical advantages over currently available forms of treatment. Methods. Experimental scoliosis was created in 40 goats using a posterior asymmetric tether with convex rib resection and concave rib tethering for a period of up to 15 weeks. Twenty-seven goats with progressive deformities were used for subsequent study and randomized into 4 treatment groups: group I, anterior thoracic stapling with removal of the posterior tether; group II, removal of the posterior tether only; group III, anterior thoracic stapling with persistent posterior tethering; and group IV, persistent posterior tethering with no treatment. The treatment period lasted an additional 6 to 14 weeks. Staple backout was graded radiographically. After killing the goats, histology and disc biochemistry analyses were conducted. Results. The goats in group I corrected from an initial 57 of curvature to 43 over the duration of the treatment period. Group II goats, which served as a control for group I, corrected from 67 to 60 during the treatment period. Group III goats demonstrated a modest correction from 65 to 63 with the stapling procedure, whereas group IV goats ( controls for group III) progressed from 55 to 67 with a persistent posterior tether during the treatment period. The difference between the correction in group III and progression in group IV was statistically significant (P = 0.002). Complications were limited to partial staple backout in 27% of 56 staples. Conclusions. The results of this study support the efficacy of an anterior thoracic staple in correcting moderately severe scoliosis and halting the progression of more malignant scoliosis without fusion in a goat model.