Vertebral Fixation Rod Shaping With Variable Compliance Control
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Solution Overview
Problem
Current methods for shaping vertebral fixation rods during spinal fusion surgery are prone to inaccuracies due to manual bending and require additional imaging, which can expose patients and staff to radiation, and do not account for varying spinal deformities and dynamic stability needs.
Innovation Solution
A robotic spinal surgery system that uses preoperative images and intraoperative feedback to accurately bend rods to match the shape of pedicle screw positions, employing motorized plungers and a rod thinning module to adjust the rod's shape and flexibility according to the surgical plan, allowing for three-dimensional shaping and variable compliance along the spine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual bending tools are used to shape the rod during surgery, then the surgeon can adjust the rod to match the spine curvature, but the positioning accuracy deteriorates due to visual judgment errors and manual manipulation limitations
Solution Approach 1:
The rod is pre-shaped using a computer-aided system before surgery based on pre-operative imaging and planning. The shaping is performed in advance rather than during surgery, allowing for precise calculation of the required curvature to match the patient's spinal anatomy, thereby eliminating manual manipulation errors while maintaining ease of the overall surgical procedure
Solution Approach 2:
The manual mechanical bending process is replaced with a computer-aided shaping system that uses imaging data and computational algorithms to determine the precise rod geometry. This substitution of mechanical manual操作 with a computational design system dramatically improves positioning accuracy while the actual implantation remains straightforward
2Manufacturing precision
If additional intraoperative imaging is performed to determine rod shape, then the positioning accuracy improves, but radiation exposure to patient and staff increases
Solution Approach 1:
All necessary imaging (CT or MRI scans) is performed pre-operatively to create a three-dimensional model of the patient's spine. The rod shaping is then calculated and executed based on this pre-acquired imaging data before the patient enters the operating room. This eliminates the need for additional intraoperative imaging, thereby maintaining high positioning accuracy while avoiding extra radiation exposure to the patient and surgical staff
Solution Approach 2:
A digital three-dimensional copy or model of the patient's spinal anatomy is created from pre-operative images. This digital model is used to calculate and shape the rod without needing to acquire new images during surgery. The digital copy serves as the basis for precise rod fabrication, eliminating the need for repeat imaging and associated radiation exposure
3Stability of the object's composition
If a rigid rod is used to connect all vertebrae, then structural stability improves, but the ability to preserve natural spinal motion deteriorates
Solution Approach 1:
The rod is designed with varying properties along its length, with different sections having different levels of flexibility or compliance. This allows the rod to provide rigid stabilization in regions requiring fusion while maintaining flexibility in regions where natural motion should be preserved, thus simultaneously achieving both structural stability and adaptability to preserve spinal function
Solution Approach 2:
The rod system incorporates dynamic characteristics through variable compliance sections that can adapt to the mechanical requirements of different spinal segments. The rod transitions from a purely static rigid structure to a dynamic system that can accommodate varying degrees of motion, providing stability where needed while preserving natural spinal mechanics in non-fusion regions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise, radiation-free shaping of vertebral fixation rods that adapt to individual spinal deformities, reducing manual effort and radiation exposure, while providing dynamic stability by varying the rod's compliance to meet specific fusion and motion preservation needs.
Implementation Method 1
a plunger positioned to apply a bending force to the rod at a predetermined location along the length of the rod such that the rod is shaped in accordance with a surgical plan
Implementation Method 2
at least one rod thinning element disposed such that the cross section of the rod can be reduced at predetermined locations along the length of the rod
Data Source
AI summary
A system for rod bending for use in robotic spinal surgery, enabling the correct bending of a fusion rod to match the shape required to accurately pass through the heads of the pedicle screws. The system uses data generated by information provided to the robot by the surgeon's preoperative plan, optionally augmented by feedback from the robot control system of deviations encountered intraoperatively. Such deviations could occur, for example, when the surgeon decides intraoperatively on a different trajectory or even to skip screws on one vertebra, in which case, the robot will be commanded to perform the alternative procedure, with commensurate instructions relayed to the control system of the rod-bending machine. The system is also able to thin down the rod at predetermined locations along its length, adapted to be at selected intervertebral locations, for maintaining limited flexibility between vertebrae, instead of fixating them.