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

Oper Neurosurg (Hagerstown). 2018 Apr 1;14(4):449-456. doi: 10.1093/ons/opx151.


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.

Publication types

  • Multicenter Study

MeSH terms

  • Female
  • Humans
  • Kyphosis / surgery*
  • Lordosis / surgery*
  • Male
  • Middle Aged
  • Osteotomy / instrumentation*
  • Osteotomy / methods
  • Postoperative Complications / etiology
  • Postoperative Complications / prevention & control
  • Prosthesis Failure*
  • Pseudarthrosis / prevention & control*
  • Retrospective Studies
  • Spinal Fusion / instrumentation
  • Spinal Fusion / methods