Accuracy of screw placement during vertebral body tethering using fluoroscopic guidance and anatomic landmarks

Purpose To determine the accuracy of screw placement using fluoroscopy and anatomic landmarks during vertebral body tethering (VBT) surgery. Methods Ten patients with 73 VBT screws were converted to posterior spinal fusion (PSF) after continued curve progression. The positions of each VBT screw were analyzed using intraoperative computed tomography (CT) scans performed for image guidance during VBT. Differences for screws placed using an open versus thoracoscopic approach were noted for the screw position in each vertebra, distance from the spinal canal, unicortical versus bicortical placement, the distance of screw tips from the thoracic aorta, and impingement of screws on adjacent rib heads. Results Seventy three (73) screws in ten (10) patients were available for analysis. Only 21% of screws were placed traversing the middle one-third of the vertebral body, without spinal canal penetration, with the distal tip placed unicortically or bicortically as planned, and without touching the thoracic aorta. The rates of non-ideal screw placement were not significantly different for screws placed via thoracoscopic versus open approaches. Five (5) screws (6.8%) penetrated the spinal canal 1-2 mm, but without known clinical sequelae. Conclusion The majority of VBT screws available for analysis were placed in non-ideal positions, suggesting that accurate screw placement using intraoperative fluoroscopy and anatomic landmarks can be challenging, but without adverse clinical consequences.