A Central Hook–Rod Construct for Osteotomy Closure

Abstract

A retrospective consecutive case series. To illustrate a new surgical technique for closing osteotomies in fixed sagittal imbalance patients, and to evaluate the radiographic outcomes and complications. During an osteotomy site closure, various techniques were used, most of which involve patient positioning, rod cantilevering, extending the fixation points, allowing less correction, and compressing through pedicle fixation points. Most of these techniques place added stress on the spinal pedicle screw fixation points, which may lead to screw loosening and eventual fixation failure. We used a central compression hook-rod construct for osteotomy closure to avoid adding compression force to the pedicle screws. Twenty-three consecutive patients in whom fixed sagittal imbalance was treated with a lumbar pedicle subtraction osteotomy or multilevel Smith-Petersen Osteotomies (SPO) using a central compression hook-rod construct for osteotomy closure were analyzed. Compression hooks were inserted into the fusion mass above and below the osteotomy site and centrally attached to a short rod. Compression forces were applied to securely close the osteotomy site. The mean age was 49.0 years (range, 33-75 years). Diagnoses included 11 scoliosis, 10 degenerative sagittal imbalance, and 2 ankylosing spondylitis patients. All but 2 cases were revisions. Sixteen patients had a pedicle subtraction osteotomy, and 7 had multilevel SPOs. A radiographic and clinical analysis was performed to evaluate the efficacy and possible complications of this technique. Overall, lumbar lordosis increased an average of 31 degrees (range, 11 degrees -68 degrees ) and local lordosis through the osteotomy site increased by an average of 28 degrees (range, 3 degrees -47 degrees ). The C7 sagittal plumbline improved an average of 109 mm (range, 11-240 mm). In all cases, the osteotomy closures were performed without screw loosening or loss of correction intraoperatively. There were no hook-rod construct failures, but one transient root paresis, which might be related to this method. There was no pseudarthroses or significant correction loss after surgery. A central hook-rod construct is a safe, quick, controlled, and effective method for spinal osteotomy site closure. It may add strength to the overall construct and avoids the placement of direct compression force on the main pedicle screw fixation points that may lead to screw loosening during the osteotomy site closure, and ultimately to fixation failure.