A Dual-Screw Technique for Vertebral Compression Fractures via Robotic Navigation in the Osteopenic Lumbar Spine: An In-Vitro Biomechanical Analysis

Abstract

Study Design: Biomechanical cadaveric study. Objectives: Multi-rod constructs maximize posterior fixation, but most use a single pedicle screw (PS) anchor point to support multiple rods. Robotic navigation allows for insertion of PS and cortical screw (CS) within the same pedicle, providing 4 points of bony fixation per vertebra. Recent studies demonstrated radiographic feasibility for dual-screw constructs for posterior lumbar spinal fixation; however, biomechanical characterization of this technique is lacking. Methods: Fourteen cadaveric lumbar specimens (L1–L5) were divided into 2 groups (n = 7): PS, and PS + CS. VCF was simulated at L3. Bilateral posterior screws were placed from L2–L4. Load control (±7.5Nm) testing performed in flexion-extension (FE), lateral bending (LB), axial rotation (AR) to measure ROM of: (1) intact; (2) 2-rod construct; (3) 4-rod construct. Static compression testing of 4-rod construct performed at 5 mm/min to measure failure load, axial stiffness. Results: Four-rod construct was more rigid than 2-rod in FE (P