Avoiding Screw Fixation Failure during Osteotomy Closure with the use of a Central Hook/Rod Construct

Purpose: There are various techniques used to close an osteotomy site, most of which involve patient positioning, rod cantilevering, or compression through points of pedicle fixation. All of these techniques place added stress on the spinal fixation points and may lead to loosening and eventual fixation failure. The purpose was to evaluate the effectiveness of a central hook/rod construct utilized as a closing device following spinal osteotomy(ies).

Methods: 31 consecutive patients in whom fixed sagittal imbalance (FSI) was treated with a lumbar pedicle subtraction osteotomy (PSO) or multilevel Smith-Petersen Osteotomies (SPO) utilizing a central compression hook/rod construct for osteotomy closure were analyzed. Compression hooks were inserted into the fusion mass above and below the osteotomy and centrally attached to a short rod. Compression forces were applied to securely close the osteotomy site. The mean age was 49.2 years (range 27-76). Diagnoses included: two ankylosing spondylitis, 25 scolioses, and four degenerative spondylolistheses of which all but two cases were revisions. 22 patients had a PSO, and nine multilevel SPOs. A radiographic and clinical analysis was performed to evaluate the efficacy and possible complications of this technique. (See Figure)

Results: Overall, lumbar lordosis increased an average of 31.0º (range 11-68º) and local lordosis through the osteotomy site increased by an average of was 26.3 (range 11-47º). The C7 sagittal plumbline improved with an average of 8.6cm (range 3-237cm). There were no failures of the hook/rod construct and no neurological complications due to this method for osteotomy closure.

Conclusions: A central hook/rod construct is a safe, quick, controlled, and effective method for spinal osteotomy site closure. It adds strength to the overall construct and avoids the placement of undue stress across the main points of pedicle fixation that can lead to screw loosening and ultimately to fixation failure.