Comprehensive In Silico Evaluation of Accessory Rod Position, Rod Material and Diameter, Use of Cross-connectors, and Anterior Column Support in a Pedicle Subtraction Osteotomy Model: Part II. Issue 1 (1st January 2021)

• Record Type: Journal Article
• Authors: Jazini, Ehsan; Gelb, Daniel E.; Tareen, Jarid; Ludwig, Steven C.; Harris, Jonathan A.; Amin, Dhara B.; Wang, Wenhai; Van Horn, Margaret R.; Patel, Pavan D.; Mirabile, Belin A.; Bucklen, Brandon S.
• Is Part Of: Spine. Volume 46:Issue 1(2021)
• Publication Date: 2021-01-01
• Subjects: adult spinal deformity -- anterior lumbar interbody fusion -- cadaveric biomechanics -- finite element analysis -- pedicle subtraction osteotomy -- strain; Spine -- Abnormalities -- Periodicals; Spine -- Diseases -- Periodicals; Spine -- Surgery -- Periodicals; 616.73005
• DOI: 10.1097/BRS.0000000000003720
• Languages: English
• ISSNs: 0362-2436

Abstract

Abstract : Study Design: In silico finite element study. Objective: The aim of this study was to evaluate effects of six construct factors on rod and screw strain at the lumbosacral junction in an in silico pedicle subtraction osteotomy (PSO) model: traditional inline and alternative Ames-Deviren-Gupta (ADG) multi-rod techniques, number of accessory rods (three-rod vs. four-rod), rod material (cobalt-chrome [CoCr] or stainless steel [SS] vs. titanium [Ti]), rod diameter (5.5 vs. 6.35 mm), and use of cross-connectors (CC), or anterior column support (ACS). Summary of Background Data: Implant failure and pseudoarthrosis at the lumbosacral junction following PSO are frequently reported. Clinicians may modulate reconstructs with multiple rods, rod position, rod material, and diameter, and with CC or ACS to reduce mechanical demand. An evaluation of these features' effects on rod and screw strains is lacking. Methods: A finite element model (T12–S1) with intervertebral discs and ligaments was created and validated with cadaveric motion data. Lumbosacral rod and screw strain data were collected for 96 constructs across all six construct factors and normalized to the Ti 2-Rod control. Results: The inline technique resulted in 12.5% to 51.3% more rod strain and decreased screw strain (88.3% to 95%) compared to ADG at the lumbosacral junction. An asymmetrical strain distribution was observed in the three-rod inline technique in comparison to four-rod, which was more evenly distributed. Regardless of construct features, rod strain was significantly decreased by rod material (CoCr > SS > Ti), and increasing rod diameter from 5.5 mm to 6.35 mm reduced strain by 9.9% to 22.1%. ACS resulted in significant reduction of rod (37.8%–59.8%) and screw strains (23.2%–65.8%). Conclusion: Increasing rod diameter, using CoCr rods, and ACS were the most effective methods in reducing rod strain at the lumbosacral junction. The inline technique decreased screw strain and increased rod strain compared to ADG. Level of Evidence: N/A. Abstract : Supplemental Digital Content is available in the textPseudoarthrosis at the lumbosacral junction is common following lumbar osteotomy. Multirod techniques, varied rod material and diameter, accessory rod positions, cross-connectors, and anterior lumbar interbody spacers were tested to elucidate factors minimizing lumbosacral rod and screw strain. Cobalt chrome rods, 6.35-mm rods, and anterior column support reduced both strains.