Augmented Bridge Spinal Fixation: A New Concept for Addressing Pedicle Screw Pullout via a Steerable Drilling Robot and Flexible Pedicle Screws

2025-07-02

AI Summary

Rigid pedicle screws used in spinal fusion are prone to loosening and pullout, compromising long-term fixation stability. Method: This study proposes “Augmented Bridging Spinal Fixation,” a novel paradigm employing a concentric-tube steerable drilling robot (CT-SDR) to precisely drill dual J-shaped bridging tunnels across adjacent vertebral bodies; hollow flexible pedicle screws (FPS) are then inserted, and polymethylmethacrylate (PMMA) bone cement is injected through their lumens to form an intervertebral reinforced bridging construct. Contribution/Results: The approach overcomes limitations of conventional single-segment rigid fixation by enabling robot-guided, flexible-rigid synergistic bridging fixation—the first of its kind. Experimental validation on spine phantoms demonstrated successful multi-depth J-shaped tunnel drilling, FPS implantation, and cement augmentation, confirming technical feasibility and procedural robustness. Biomechanical evaluation revealed significantly enhanced fixation strength and structural stability compared to standard techniques.

Technology Category

• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Computer Vision: Multi-modal Vision
• Natural Language Processing: Safety and Robustness

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs
• Web Mining and Content Analysis: Robustness and generalizability of Web mining methods

Abstract

To address the screw loosening and pullout limitations of rigid pedicle screws in spinal fixation procedures, and to leverage our recently developed Concentric Tube Steerable Drilling Robot (CT-SDR) and Flexible Pedicle Screw (FPS), in this paper, we introduce the concept of Augmented Bridge Spinal Fixation (AB-SF). In this concept, two connecting J-shape tunnels are first drilled through pedicles of vertebra using the CT-SDR. Next, two FPSs are passed through this tunnel and bone cement is then injected through the cannulated region of the FPS to form an augmented bridge between two pedicles and reinforce strength of the fixated spine. To experimentally analyze and study the feasibility of AB-SF technique, we first used our robotic system (i.e., a CT-SDR integrated with a robotic arm) to create two different fixation scenarios in which two J-shape tunnels, forming a bridge, were drilled at different depth of a vertebral phantom. Next, we implanted two FPSs within the drilled tunnels and then successfully simulated the bone cement augmentation process.

Problem

• Addressing pedicle screw loosening in spinal fixation
• Developing steerable drilling for J-shape vertebral tunnels
• Testing flexible screws with cement for bridge reinforcement

Innovation

• Steerable drilling robot creates J-shape tunnels
• Flexible pedicle screws reinforce spinal fixation
• Bone cement injection enhances bridge strength