A Novel 4-Rod Technique Offers Potential to Reduce Rod Breakage and Pseudarthrosis in Pedicle Subtraction Osteotomies for Adult Spinal Deformity Correction

Abstract BACKGROUND Pedicle subtraction osteotomy (PSO) can be used to treat rigid sagittal plane deformities. Nonunions and rod breakages are known complications of PSO. OBJECTIVE To assess outcomes of 2 methods of posterior instrumentation for PSO, traditional 2 rods vs a novel 4-rod technique in which 2 additional rods span only the osteotomy level. METHODS This study was a retrospective, radiographic review of consecutive PSOs performed at 2 centers. The primary difference in technique between the centers was the use of 4 rods including 2 independent rods attached only to the vertebral levels immediately adjacent to the PSO (group 1, n = 29 patients) vs the traditional 2-rod technique (group 2, n = 20 patients). RESULTS Demographics and preoperative to postoperative radiographic measurements were similar between the study groups, including the PSO wedge resection angle ( P = .56). The rod breakage rate was 25% with 2 rods and 0% with 4 rods ( P = .008), and the pseudarthrosis rate with 2 rods was 25% and with 4 rods was 3.4% ( P = .035). The patient with pseudarthrosis from group 1 had an infection and developed pseudarthrosis only after instrumentation removal. Rates of other complications did not differ significantly between the study groups. CONCLUSION This study provides a comparison between 2 techniques for rod placement across a PSO and suggests that the described novel 4-rod technique may help to reduce the rates of pseudarthrosis and rod failure. It will be important to confirm these findings in a prospectively designed study with multiple institutions in order to better control for potentially confounding factors.