Sterile Rod Shape Template for Accurate Posterior Spinal Bending
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Solution Overview
Problem
Surgeons face challenges in accurately verifying the manually bent spinal rod's size and shape within the sterile operation area, leading to complications such as proximal junction kyphosis, proximal junctional failure, and screw pull-out during posterior spinal stabilisation surgeries, due to imperfect contoured rod shapes and high forces required for fixation.
Innovation Solution
A rod shape visualisation device comprising a sterile case and a visualisation template, which allows the surgeon to verify the desired spinal rod shape intra-operatively within the sterile area, using a non-sterile template that can be safely transferred and stabilized to provide accurate feedback on the rod's size and shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-sterile template with visualisation information is placed in the sterile operation area, then the surgeon can verify the desired rod shape, but the risk of contamination increases
Solution Approach 1:
A sterile barrier (sterile pouch or drape) is introduced as an intermediary between the non-sterile template and the sterile operation field. The template is placed inside the sterile barrier, allowing visual verification of rod shape while preventing contamination. The barrier acts as a mediator that permits optical information transmission while blocking microbial contamination.
Solution Approach 2:
The desired rod shape is represented as a visual copy (template or printout) of the pre-operative planning. This copy contains all necessary geometric information (curvature, angles, dimensions) and can be placed in the sterile field within a barrier for verification without requiring the actual planning software or imaging equipment in the sterile area.
2Manufacturing precision
If multiple rod bendings are performed to achieve the desired shape, then the rod can be adjusted to match the plan, but the risk of fatigue failure increases
Solution Approach 1:
The desired rod shape is predetermined through pre-operative planning, and a visual template of this planned shape is prepared beforehand. During surgery, the rod is bent once or twice to match this pre-planned template, rather than requiring multiple iterative adjustments. This preliminary preparation reduces the number of bending operations needed.
Solution Approach 2:
The visual template serves as immediate feedback during the rod bending process. The surgeon can continuously compare the bent rod against the template to verify shape accuracy, allowing for precise single-stage or two-stage bending without multiple trial-and-error adjustments, thereby reducing fatigue from repeated bending.
3Measurement precision
If the rod shape is verified using intra-operative X-ray images, then the desired shape can be confirmed, but the process becomes time-consuming and complex
Solution Approach 1:
Instead of requiring complete intra-operative X-ray verification of the entire rod shape, the visual template provides immediate visual feedback on the critical geometric parameters (curvature, angles). This partial verification method is sufficient for most cases and avoids the time-consuming X-ray process, reserving imaging for only when absolutely necessary.
Solution Approach 2:
A visual copy (template) of the planned rod shape is used instead of relying on intra-operative imaging. This template contains all necessary geometric information in a visually accessible format, allowing rapid verification without activating imaging equipment, thus saving significant time during the surgical procedure.
4Strength
If high forces are applied to fixate the rod in the pedicle screw, then the rod can be secured, but complications such as screw pull-out and PJK increase
Solution Approach 1:
The rod shape is predetermined and visually planned before surgery. By having the exact desired geometry established in advance and using it as a template for bending, the rod achieves optimal fit and contact with the pedicle screws from the first fixation attempt, eliminating the need for high forces or multiple adjustments that could compromise the fixation or surrounding bone.
Solution Approach 2:
The verification process is changed from a mechanical/force-based system (relying on high fixation forces and post-operative imaging) to a visual information system. The template provides visual confirmation of correct rod geometry, allowing precise shaping that reduces the need for high fixation forces, thereby substituting visual information for mechanical force application.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E~1G
AI summary
A rod shape visualisation device (1 ) is proposed for providing information on the desired shape of a posterior spinal rod during a bending process whilst being arranged in a sterile operation area. The rod shape visualisation device (1 ) comprises: (a) a sterile case (10) comprising a housing portion (11) including an entrance aperture (12) and a cover (13), sized and shaped to seal the entrance aperture (12), the sterile case (10) further comprising an inner lumen (14) configured to come in contact with non-sterile or sterile objects, and (b) a non-sterile or sterile visualisation template (40) comprising a displaying side providing information on the desired shape of a posterior rod. The rod shape visualisation device (1 ) defines a first, open state in which the cover (13) is open, and a second, closed state in which the cover (13) is closed, wherein in the closed state, the displaying side of the visualisation template (40) is visibly arranged in the inner lumen (14).