Acetabular Cup Alignment Using Pre-Operative X-Ray Pelvic Tilt
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Solution Overview
Problem
Current methods for aligning acetabular cups during hip surgery are inadequate, as they rely on assumptions about pelvic position, leading to potential dislocation and excessive wear due to inaccurate alignment, and existing navigation systems are invasive, costly, and require extensive training.
Innovation Solution
A method using pre-operative lateral x-ray images to determine natural pelvic tilt angles, combined with intra-operative orientation technology to adjust for pelvic movement during surgery, allowing for precise alignment of acetabular cups without invasive pins or multiple x-rays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional alignment guides referencing the surgical table are used, then the procedure is simple and quick, but the acetabular cup alignment accuracy deteriorates due to unrecognized pelvic position changes
Solution Approach 1:
The patent replaces the mechanical reference system (alignment guide referencing the surgical table) with an image-guided navigation system. The system uses pre-operative and intra-operative x-ray images to establish a virtual reference frame based on pelvic anatomy rather than the surgical table, allowing accurate cup alignment even when the pelvis shifts during surgery. This substitution of mechanical reference with image-based anatomical reference resolves the contradiction between procedural simplicity and alignment accuracy.
2Manufacturing precision
If invasive navigation systems with pins and multiple x-rays are used, then alignment precision improves, but patient trauma and radiation exposure increase
Solution Approach 1:
The patent performs the critical alignment planning action in advance by obtaining pre-operative x-ray images and establishing the desired cup orientation relative to pelvic anatomy before surgery. This preliminary action allows the surgical team to plan the exact approach and angle needed, then simply execute the pre-planned alignment during surgery using intra-operative verification images, avoiding the need for continuous navigation during the procedure and reducing both radiation exposure and invasiveness.
Solution Approach 2:
The system provides feedback by comparing the actual cup position (measured during surgery) with the pre-planned target position derived from pre-operative images. Intra-operative x-ray images are used to verify alignment, and any deviations can be corrected before final implantation. This feedback loop ensures high precision without requiring invasive continuous navigation, as the system only needs verification at key stages rather than constant guidance.
3Device complexity
If surgeons rely on experience to position the cup, then the procedure requires no additional equipment, but alignment reliability deteriorates especially for less experienced surgeons
Solution Approach 1:
The patent introduces an image-guided navigation system as an intermediary between the surgeon's intent and the actual cup placement. Rather than relying directly on surgeon experience alone, the system provides objective anatomical references and alignment guidance based on x-ray imaging. This intermediary translates the desired alignment (determined from pre-operative planning) into verifiable intra-operative measurements, making the process more reliable and less dependent on individual surgeon experience while still keeping the equipment relatively simple.
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
This approach enables accurate alignment of acetabular cups, reducing the risk of dislocation and wear, improving surgical efficiency, and minimizing radiation exposure and invasive procedures.
Implementation Method 1
A method for aligning an acetabular cup includes obtaining a pre-operative lateral x-ray image... At least one intra-operative x-ray image is obtained... The x-ray images are used to identify pelvic anatomical landmarks and calculate pelvic tilt angles
Data Source
AI summary
A method is used for aligning an acetabular cup insertion instrument by taking a single lateral view pre-operative digital x-ray of a standing patient's pelvis. The natural pelvic tilt angle is determined by locating an anterior pelvic plane (APP) which is defined by first, second and third points on the anterior of the pelvis and determining the angle between the APP and a coronal plane perpendicular to the surface on which the patient is standing. The patient is then placed on a surface of an operating room table in a supine position. A position tracking device is placed on the patient's pelvis to track movement. Thereafter an operating room navigation or orientation system is used to relocate the APP defined by the first, second and third points. A cup insertion instrument having a position tracking device thereon is oriented using the navigation or orientation system.