Surgical Technique for Balancing Posterior Spinal Fusions to the Pelvis Using the T Square of Tolo

BACKGROUND:Correcting pelvic obliquity and improving sitting balance in neuromuscular scoliosis often requires fixation to the pelvis. We describe the use of a T square instrument to assist intraoperatively in evaluating the alignment of these curves and achieving balance in the coronal plane. METHODS:The T square instrument was constructed with a vertical limb perpendicular to 2 horizontal limbs in a T formation. At the conclusion of the instrumentation and preliminary reduction maneuvers, the T square was positioned with the horizontal limbs parallel to the pelvis and the vertical limb in line with the central sacral line. If the spine and pelvis were well balanced, fluoroscopic images demonstrated that the superior aspect of the vertical limb of the T square was crossing the vertebral body of T1. If this was not shown, then some combination of compression, distraction, or a change in the contouring of the rods was performed until this balance was achieved. RESULTS:In this series, we describe case examples in which the T square has been successfully used to aid in achieving balance in the coronal plane. This technique helps to overcome the challenges with positioning and imaging often encountered in managing these long, rigid curves. The T square is a useful adjunct in balancing posterior spinal fusions and evaluating the correction of pelvic obliquity in cases of neuromuscular scoliosis. CONCLUSIONS:This novel, yet simple, T square technique can be used for any method of posterior spinal fusion with lumbopelvic fixation to assist in the intraoperative evaluation and achievement of balance in the coronal plane and has become routine at our institution. LEVEL OF EVIDENCE:IV