Motion Preservation Following Vertebral Body Tethering: An Analysis of 103 Patients

Motion-sparing approaches to scoliosis surgery such as vertebral body tethering (VBT) are growing in popularity. There is limited data evaluating motion preserving after the different tether approaches. We hypothesized that spinal motion would be preserved in both the sagittal and coronal planes in patients after thoracic, lumbar, and bilateral vertebral body tethering procedures.

This was a retrospective comparison study of adolescent idiopathic scoliosis (AIS) patients who underwent VBT. Preoperative and postoperative coronal range of motion across the instrumented levels were compared using a standing microdose slot-scanning protocol. Flexion/extension radiographs were evaluated postoperatively to assess preserved sagittal arc of motion. Patients with known cord breakage were excluded.

The mean age at surgery was 12.9 years (range: 9.4 to 16.5) with mean follow-up period of 2.8 years. Skeletal maturity, defined as Risser sign ≥5, was observed in 29 patients. (26.9%). Overall, mean thoracic coronal arc of motion for postoperative VBT patients was 10 degrees in the thoracic spine and 20 degrees in the lumbar. This was a 59% (24 to 10 deg.) decrease in thoracic range of motion and a 51% (40 to 20 deg.) decrease in lumbar range of motion. Right-sided motion was greater in patients with thoracic instrumentation, whereas left-sided motion was greater in patients with lumbar instrumentation. In addition, patients also retained sagittal motion. Patients with single thoracic tethers had a total arc of motion of 22 degrees, whereas patients with single lumbar tethers had a total arc of motion of 25 degrees. It was noted that both groups had a greater degree of flexion than extension.

Patients with single thoracic tethers saw a 60% decrease in the total coronal arc of motion. Patients with single lumbar tethers saw a 57% decrease in coronal motion. Patients had around 20 to 25-degree arc of motion preserved over the instrumented segments in the sagittal plane. Further work is needed to outline the functional benefits of motion preservation after VBT.

Level III (retrospective cohort study).