Hip Surgery Navigation Using Pelvic Coordinate System
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Solution Overview
Problem
Current methods for determining leg length, offset, and anterior-posterior position changes during hip surgery are inaccurate and time-consuming, particularly due to difficulties in establishing a femoral coordinate system in deformed hip joints, leading to unstable joints and potential dislocation.
Innovation Solution
A system and method using position tracking frames for the femur and pelvis, combined with a navigation engine and image generator, to establish a pelvic coordinate system and guide the surgeon in returning the leg to a predetermined orientation, allowing for precise calculation of leg length, offset, and AP position changes without requiring a femoral coordinate system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surgical navigation techniques are used to track bone positions, then measurement precision of leg length and offset changes is improved, but device complexity increases due to tracking frames and coordinate systems
Solution Approach 1:
The patent extracts and eliminates the femoral coordinate system from the surgical navigation process, retaining only the pelvic coordinate system. This simplification maintains measurement precision for leg length and offset changes while reducing device complexity by removing the need to establish and track a separate femoral coordinate system.
Solution Approach 2:
The pelvic coordinate system serves multiple functions: it tracks both the pelvis position and the femur position relative to the pelvis, enabling calculation of leg length, offset, and AP position changes. This multi-functionality eliminates the need for a separate femoral coordinate system, reducing overall system complexity while maintaining measurement capabilities.
2Measurement precision
If a femoral coordinate system is established to calculate leg length changes, then measurement accuracy is improved, but time consumption increases due to difficulty in calculating center of rotation in deformed joints
Solution Approach 1:
The patent removes the time-consuming step of calculating the femoral center of rotation by eliminating the femoral coordinate system requirement. Instead, all measurements are referenced to the pelvic coordinate system, which is established once and used throughout the procedure to track femoral position changes.
Solution Approach 2:
The pelvic coordinate system is established once before the procedure begins and serves as a permanent reference frame. This preliminary establishment eliminates the need for repeated center of rotation calculations during surgery, significantly reducing time consumption while maintaining measurement accuracy.
3Device complexity
If physical measurements with rulers and gauges are used, then device complexity is reduced, but measurement precision of leg length changes deteriorates
Solution Approach 1:
The patent replaces mechanical measurement tools (rulers and gauges) with an optical/electromagnetic tracking system. The tracking frames with sensors provide automated, precise measurement of bone position changes in three dimensions, eliminating the need for manual physical measurements while significantly improving measurement precision.
4Loss of time
If preoperative images are used to plan component placement, then time consumption during surgery is reduced, but measurement precision of actual position changes deteriorates due to unknown magnification and incorrect planes
Solution Approach 1:
The patent implements real-time feedback through the tracking system, which continuously monitors and provides actual position data of the femur relative to the pelvis during surgery. This real-time information allows surgeons to make immediate adjustments and verify component placement accuracy, combining the time efficiency of preoperative planning with the precision of intraoperative measurement.
Data Source
AI summary
A system and method for use during hip surgery includes a position frame that is removably secured to the patient's femur. The system further includes a tracking unit and navigation engine that establish a pelvic coordinate system and, with the patient's leg placed in a predetermined orientation, capture the location of the femoral position frame within the pelvic coordinate system. The system further includes an image generator configured to display one or more images for directing the surgeon to return the patient's leg to the predetermined orientation following a trial reduction based upon the previously captured position. A leg change determination engine compares the current, post-reconstruction position of the femoral position tracking frame with the previously captured, pre-reconstruction position to derive leg length, offset, and anterior-posterior change values. The change values are then provided to the surgeon for evaluating the suitability of the trial reduction.