Pedicle stress shielding following growing rod implantation: case report

Growing rod surgery for skeletally immature patients helps correct severe scoliosis while allowing continued spinal column growth. Previous reports have studied vertebral body changes following growing rod surgery, but there are currently no published reports on alterations in pedicle morphology. Given the potential need for definitive spinal fusion with pedicle screw instrumentation, an awareness of changes in pedicle morphology is critical. A morphometric analysis of pedicles was performed using 3D reconstructions of 3 CT scans (preoperative and at 3 and 6 years) obtained in a young girl with infantile idiopathic scoliosis (T7 apex) who underwent unilateral rib-to-spine growing rod (2nd-4th ribs to L1) implantation with lengthening every 6 months for 6 years. The pedicle widths on the growing rod side from T5 to T9 (apex ± 2) were all smaller at 6 years postoperatively than preoperatively, while the same-level pedicles opposite the device significantly increased in width. These findings support anecdotal intraoperative reports by surgeons and provide evidence of pedicle stress shielding due to growing rod distraction and force deprivation.