A novel 4-rod technique offers potential to reduce rod breakage and pseudarthrosis in pedicle subtraction osteotomies for adult spinal deformity correction

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 2methods of posterior instrumentation for PSO, traditional 2 rods vs a novel 4-rod technique inwhich 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 thePSO(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 fromgroup 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.