| Abstrakt: |
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< .001), LB (P< .001), AR (P< .001). Screw technique had no significant effect on FE (P= .516), LB (P= .477), or AR (P= .452). PS + CS 4-rod construct was significantly more stable than PS group (P= .032). Stiffness of PS + CS group (445.8 ± 79.3 N/mm) was significantly greater (P= .019) than PS (317.8 ± 79.8 N/mm). Similarly, failure load of PS + CS group (1824.9 ± 352.2 N) was significantly greater (P= .001) than PS (913.4 ± 309.8 N).Conclusions Dual-screw, 4-rod construct may be more stable than traditional rod-to-rod connectors, especially in axial rotation. Axial stiffness and ultimate strength of 4-rod, dual-screw construct were significantly greater than rod-to-rod. In this study, 4-rod construct was found to have potential biomechanical benefits of increased strength, stiffness, stability. |
