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Scientific Session

Scientific Session II: Spine

(SS#II) Sanford Larson Award for Best Research (2023 Award Winner): Investigation of 3D Printed Thoracic Pedicle Behavior During Instrumentation of Single vs. Combined Thermoplastic Polymers

Saturday, April 22, 2023
2:53pm – 2:58pm PST
Location: Los Angeles Convention Center, 408A

    Presenting Author(s)

  • William Clifton, MD

    Attending Neurosurgeon
    Cleveland Clinic Main Campus
    Cleveland, Ohio, United States

Disclosure(s):
William Clifton, MD: Bard: Consultant (Ongoing); NervOrg: Consultant (Ongoing); Symgery: Royalty Recipient (Ongoing)
Introduction: Three-dimensional printing (3DP) has shown promise in replicating the corticocancellous interface (CCI) of human vertebrae. Human studies have demonstrated plasticity in thoracic pedicle dimensions during instrumentation. This study investigated the behavior of two established methods of 3DP models during thoracic pedicle screw placement to determine the potential of providing a novel medium for biomechanical assessment of spinal instrumentation.

Methods: Three distinct anonymized DICOM files of separate human thoracic spines (T1-T12) were acquired. Two previously published methods of recreating the CCI using 3DP were utilized, establishing two cohorts of three distinct thoracic spines. One cohort was created using a dual material technique, and the other cohort using a standard single material infill technique. Pedicle screws were placed bilaterally in each vertebral model starting with 4.5mm diameter, and subsequently upsized 0.5mm to a maximum diameter of 9.0mm. Pedicle failure was defined as a visual breakage of the 3DP model. Screw diameter and location of the pedicle breakage were recorded. Statistical analysis was performed on the results.

Results: A total of 814 pedicle screws were placed in 72 3DP vertebral models. The average pedicle screw diameter inserted before model failure was significantly higher in the dual material cohort than the single material (7.68mm vs. 5.87mm, p< 0.0001). The number of medial breakages in the dual material cohort was found to be significantly less than the single material cohort (8.3% vs. 37.5%, p< 0.0001), and the number of lateral only breakages in the dual material model was found to be significantly higher than the single material model (89.7% vs. 61.1%, p=0.0114).

Conclusion : This study is the first of its kind to investigate the physiologic behavior of 3DP thoracic vertebral models. The combined thermoplastic model demonstrated pedicle plasticity and significantly less medial wall failures during screw insertion than the single material model, thereby simulating superior in-vivo characteristics.