Fiber Optic Bone Tracking Cable With FBG Shape Sensing
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Solution Overview
Problem
Existing computer navigation systems for orthopedic surgery face challenges with electromagnetic tracking systems due to interference from metallic objects and require invasive cortical pin placement, which can lead to complications and hinder minimally invasive procedures.
Innovation Solution
A surgical navigation system using a multi-core fiber optic cable with fiber Bragg gratings (FBGs) that is less invasive, reduces twisting and kinking, and integrates with a low-profile bone pin to provide accurate shape sensing, allowing for non-invasive tracking of surgical instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic tracking is used for computer navigation, then tracking capability is provided, but interference from metallic objects occurs
Solution Approach 1:
The patent replaces electromagnetic tracking with optical fiber-based tracking. The optical fiber system uses light transmission through fiber optic cables with Bragg gratings to detect position and orientation, eliminating reliance on electromagnetic fields that are susceptible to metallic interference. This substitution of tracking mechanism resolves the contradiction by maintaining tracking capability while removing sensitivity to metallic objects in the surgical environment.
Solution Approach 2:
The patent introduces optical fiber cables as an intermediary medium between the surgical instruments and the navigation system. The fiber optic cables transmit positional information through light signals rather than electromagnetic waves, acting as a mediator that is immune to metallic interference. This intermediary approach allows reliable tracking while avoiding the harmful effects of electromagnetic interference from surgical metals.
2Reliability
If cortical pins are used to secure tracking instrumentation, then reliable registration is achieved, but tissue resection and drilling are required
Solution Approach 1:
The patent employs flexible optical fiber cables instead of rigid cortical pins for securing tracking instrumentation. The fiber optic cables can be attached to surgical instruments or bone surfaces using less invasive methods such as adhesives or minimal anchoring, eliminating the need for cortical drilling and pin insertion. This flexible approach maintains registration reliability while significantly reducing tissue trauma and procedural complexity.
Solution Approach 2:
The patent replaces the mechanical cortical pin fixation system with an optical fiber-based attachment system. Instead of using rigid pins that require drilling into bone, the system uses flexible optical fibers that can be secured with minimal invasion. This substitution reduces the mechanical complexity of bone penetration while maintaining the reliability of tracking registration through optical sensing.
3Reliability
If cortical pins are placed away from incision site, then tracking instrumentation occlusion is prevented, but pin holes serve no functional purpose
Solution Approach 1:
The patent makes the optical fiber attachment points multi-functional by placing them at or near the incision site. Unlike cortical pins that require separate placement away from incisions, the flexible fiber optic cables can be anchored at the incision site itself, serving both as a secure attachment point and as a functional entry point for the instrument. This eliminates the waste of healthy tissue for non-functional pin placement while maintaining tracking visibility.
Solution Approach 2:
The flexible nature of optical fiber cables allows them to be routed and positioned optimally without requiring distant anchoring points. The cables can extend from the incision site along the instrument shaft, providing secure attachment near the surgical site while maintaining clear visibility of the tracking instrumentation. This flexibility eliminates the need to place anchors in distant healthy tissue, reducing unnecessary tissue loss.
4Measurement precision
If fiber optic cables are used for shape sensing, then accurate position tracking is achieved, but cable twisting and kinking cause measurement inaccuracies
Solution Approach 1:
The patent implements protective measures beforehand to prevent cable twisting and kinking from degrading measurement accuracy. This includes designing the fiber optic cable routing to minimize stress concentrations, using protective coatings or sheathing on the cables, and establishing proper anchoring and tensioning systems during installation. By cushioning against potential twisting and kinking in advance, the system maintains measurement precision and reliability throughout the surgical procedure and over time.
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
The system enhances surgical navigation accuracy, reduces patient risk and clutter in the operating room, and improves ergonomics by minimizing twisting and kinking of cables, thereby reducing errors and complications.
Implementation Method 1
A fiber optic Bragg grating (FBG) is a short segment of optical fiber that reflects particular wavelengths of light and transmits others. This is achieved by adding a periodic variation of the refractive index in the fiber core, which generates a wavelength-specific dielectric mirror.
Implementation Method 2
One such approach is to use Rayleigh scatter in standard single-mode communications fiber. Rayleigh scatter occurs as a result of random fluctuations of the index of refraction in the fiber core. These random fluctuations can be modeled as a Bragg grating with a random variation of amplitude and phase along the grating length.
Data Source
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Figure 4A~4C
AI summary
The present disclosure provides a surgical navigation system that utilizes multimodal tracking along with low profile/small diameter bone pins to fix FBG sensors to a patient. With some embodiments, a multi-core fiber optic cable having both an infrared (IR) tracking sensor disposed at a known location in the multi-core fiber optic cable and FBGs. The FBGs can be used to locate the tip of the cable relative to the IR marker, where the tip of the cable is embedded in a bone, the location of the done can be determined.