Magnetic Sensor Jigs for Precise Orthognathic Bone Alignment
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Solution Overview
Problem
Existing navigation systems for orthognathic surgery face challenges such as position detection reference modules interfering with surgery, inaccurate alignment of bone fragments, and issues with optical and magnetic navigation due to external targets or lack of visible marks, leading to difficulties in achieving precise relative positions and postures of bones.
Innovation Solution
A navigation system utilizing jigs with predefined attachment surfaces for sensors, combined with a program to generate and display three-dimensional coordinate axis images, enabling accurate alignment and movement of bones to predetermined target positions and postures using magnetic sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position detection reference module with a complicated shape is used in magnetic navigation surgery, then the position of the bone can be detected, but the module interferes with the surgery
Solution Approach 1:
The position detection reference module is divided into two parts: a simple reference module attached to the bone and a separate detection device. The reference module has a simple shape that does not interfere with surgery, while the detection device performs the measurement function remotely.
Solution Approach 2:
The detection function is extracted from the reference module and placed in a separate detection device. The reference module retained only the simple attachment structure, removing the complicated detection components that caused surgical interference.
2Measurement precision
If the position detection reference module has a shape exposed to the outside, then the position can be detected by the navigation system, but the detected position is away from the actual position of the bone
Solution Approach 1:
The magnetic sensor is nested inside a hollow cylindrical reference module that is attached directly to the bone. This nesting allows the sensor to be positioned at the exact bone location while the outer cylindrical structure provides a detectable reference shape.
Solution Approach 2:
The hollow cylindrical reference module serves as an intermediary between the bone and the navigation system. It is attached directly to the bone surface, providing an external detectable shape that accurately represents the bone's position without requiring the detection shape to be exposed or separated from the bone.
3Reliability
If a cutting guide is used to attach the position detection reference module, then the module can be attached to the bone fragment, but it takes time and effort to align the upper jaw and lower jaw
Solution Approach 1:
The reference module attachment is extracted from the cutting guide procedure. The reference module is attached directly to the bone fragment at the target position determined in preoperative planning, eliminating the need for cutting guide alignment and reducing surgical time.
Solution Approach 2:
The target attachment position is determined in advance during preoperative planning using three-dimensional simulation. This preliminary determination allows the reference module to be directly attached to the correct position without requiring time-consuming alignment procedures during surgery.
4Measurement precision
If the target for alignment is exposed to the outside from the dental splint, then distance measurement using camera can be performed, but the target obstructs the surgery and the position is away from the dentition
Solution Approach 1:
The optical measurement system (camera and reflector) is replaced with a magnetic field-based detection system. The magnetic sensor and reference module work together to enable position detection without requiring optical line-of-sight, eliminating the need for an externally exposed target.
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 supports surgeons in accurately moving and rotating bones to achieve target relative positions and postures, enhancing surgical precision and reducing interference during navigation.
Implementation Method 1
In magnetic navigation surgery, a position of a surgical instrument (non-magnetic) is detected in real time by a magnetic tracking system based on an output of a magnetic sensor attached to the surgical instrument
Implementation Method 2
In optical navigation surgery, a position of a surgical instrument is detected in real time by distance measurement using infrared rays reflected by a reflector attached to the surgical instrument
Data Source
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AI summary
A navigation system includes: an acquisition unit configured to acquire information on a position and a posture of a first sensor detected based on a signal of the first sensor, and information on a target attachment position and a target attachment posture of the first sensor with respect to a position and a posture of a second sensor detected based on a signal of the second sensor, the first sensor being inserted into an attachment portion of a first jig, which has a surface having a shape corresponding to a surface of a first bone, in a first orientation predetermined with respect to the first jig, and the second sensor being inserted into an attachment portion of a second jig, which has a surface having a shape corresponding to a surface of a second bone, in a second orientation predetermined with respect to the second jig; a derivation unit configured to derive a first relative position and a first relative posture of the first sensor based on the target attachment position, the target attachment posture, and the position and the posture of the first sensor; an information generation unit configured to generate a three-dimensional coordinate axis image representing the target attachment position and the target attachment posture and a three-dimensional coordinate axis image representing the first relative position and the first relative posture; and a display unit configured to display the three-dimensional coordinate axis image.