Segmental trans-endplate pedicle screws do not induce spinal deformity in a porcine model

Growth modulation is an established technique for limb deformity correction and is increasingly applied to spinal deformities. While distraction-based posterior and anterior compressive methods have been explored, spinal growth modulation through fixation across vertebral growth centers remains unstudied. We hypothesized that unilateral trans-endplate screws-spinal epiphysiodesis trajectory (SET) screws-could induce partial anterior growth arrest and promote scoliotic deformity in a porcine model.

Four male piglets (two experimental, two control) underwent unilateral posterior spinal instrumentation at four lower thoracic levels at eight weeks of age. Experimental animals received trans-endplate SET screws; controls received pedicle screws. Radiographs obtained three months postoperatively assessed vertebral height and Cobb angles. MRI and CT were also used to evaluate vertebral wedging, disc and facet health, physeal bars, and endplate changes.

After three months, no significant differences in coronal or sagittal Cobb angles were observed between SET and pedicle screw groups (p > 0.05). No vertebral wedging or restriction of vertical growth was seen in either group. Disc and facet health remained unchanged by Pfirrmann and Fujiwara grading. No physeal bars were identified; one SET specimen showed endplate irregularities.

In this pilot porcine model, SET screws did not produce scoliotic or kyphotic deformity. Further research is necessary to clarify the mechanisms and timing required for effective anterior spinal growth modulation.

IV.