title: Preventing Instrumentation Failure in Three-Column Spinal Osteotomy: Biomechanical Analysis of Rod Configuration.
abstract: Biomechanical analysis.
  
  
  
  To show the role of additional rods and long-term fatigue strength to prevent the instrumentation failure on three-column osteotomies.
  
  
  
  Three-column osteotomy such as pedicle subtraction osteotomy (PSO) and vertebral column resections are surgical correction options for fixed spinal deformity. Posterior fixation for the PSO involves pedicle screw-and rod-based instrumentation, with the rods being contoured to accommodate the accentuated lordosis. Pseudarthrosis and instrumentation failure are known complications of PSO.
  
  
  
  Unilateral pedicle screw and rod constructs were mounted in ultra-high-molecular-weight polyethylene blocks using a vertebrectomy model with the rods contoured to simulate posterior fixation of a PSO. Each construct was cycled under a 200 N load at 5 Hz in simulated flexion and extension to rod failure. Three configurations (n = 5) of titanium alloy rods were tested: single rod (control), double rod, and bridging rod. Outcomes were total cycles to failure and location of rod failure.
  
  
  
  Double-rod and bridging-rod constructs had a significantly higher number of cycles to failure compared with the single-rod construct (p < .05). Single-rod constructs failed at or near the rod bend apex, whereas the majority of double-rod and bridging-rod constructs failed at the screw-rod or rod-connector junction.
  
  
  
  Double-rod and bridging-rod constructs are more resistant to fatigue failure compared with single-rod constructs in PSO instrumentation and could be considered to mitigate the risk of instrumentation failure.
authors.affiliation: Department of Orthopaedic Surgery, Loma Linda University, School of Medicine, 11406 Loma Linda Dr, Suite 213, Loma Linda, CA 92354, USA.
authors.forename: Zachary S
authors.initials: ZS
authors.lastname: Jager
authors.affiliation: Department of Orthopaedic Surgery, Loma Linda University, School of Medicine, 11406 Loma Linda Dr, Suite 213, Loma Linda, CA 92354, USA.
authors.forename: Serkan
authors.initials: S
authors.lastname: İnceoğlu
authors.affiliation: Department of Orthopaedic Surgery, Loma Linda University, School of Medicine, 11406 Loma Linda Dr, Suite 213, Loma Linda, CA 92354, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Palmer
authors.affiliation: Department of Orthopaedic Surgery, Loma Linda University, School of Medicine, 11406 Loma Linda Dr, Suite 213, Loma Linda, CA 92354, USA.
authors.forename: Yusuf T
authors.initials: YT
authors.lastname: Akpolat
authors.affiliation: Department of Orthopaedic Surgery, Loma Linda University, School of Medicine, 11406 Loma Linda Dr, Suite 213, Loma Linda, CA 92354, USA. Electronic address: md4spine@yahoo.com.
authors.forename: Wayne K
authors.initials: WK
authors.lastname: Cheng
mesh_terms: D001696:Biomechanical Phenomena; D006801:Humans; D008141:Lordosis / Q000601:surgery*; D008159:Lumbar Vertebrae; D010027:Osteotomy / Q000379:methods*; D065289:Pedicle Screws; D016059:Range of Motion, Articular; D013123:Spinal Fusion; D013904:Thoracic Vertebrae; D014025:Titanium; D016896:Treatment Outcome
chemical_list: D014025:Titanium
keywords: Bridging rod; Double rod; Pedicle subtraction osteotomy; Sagittal imbalance; Spinal rod failure