Acetabular Component Positioning Using a Hemipelvic Reference Plane
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Solution Overview
Problem
Malpositioning of the acetabular component during hip arthroplasty leads to complications such as dislocation, impingement, and wear due to the variability in pelvis positioning during surgery, with existing methods like qualitative assessment of local anatomy being inaccurate and unreliable.
Innovation Solution
The use of ipsilateral hemipelvic anatomy, defined by three points on the hemipelvis, to guide the positioning of the prosthetic acetabular component, with a mechanical instrument like a tripod to establish a reliable reference plane for accurate component placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If qualitative assessment of local acetabular anatomy is used to guide component positioning, then the method is simple to perform, but the positioning accuracy is poor due to geometric errors and anatomical variability
Solution Approach 1:
The patent transitions from using two-dimensional local anatomical landmarks (transverse acetabular ligament) to utilizing three-dimensional relationships of the entire hemipelvis. By defining a reference plane through three non-collinear points on the hemipelvis, the system creates a robust 3D spatial framework that eliminates the geometric amplification of errors inherent in 2D landmark-based methods.
Solution Approach 2:
The patent divides the pelvis into functional segments by identifying specific anatomical landmarks (anterior superior iliac spine, posterior superior iliac spine, pubic tubercle) that define the hemipelvis reference plane. This segmentation allows each landmark to be independently identified and measured, improving overall positioning accuracy while maintaining procedural simplicity.
2Device complexity
If transverse acetabular ligament is used as orientation marker, then the method requires minimal equipment, but large angular errors occur due to small geometric margins at the acetabular center
Solution Approach 1:
The patent introduces a mechanical instrument with a tripod structure as an intermediary device. This instrument physically establishes the hemipelvis reference plane by contacting three anatomical landmarks, serving as a mediator between the surgeon's intent and the actual component positioning. The mechanical instrument amplifies and stabilizes the reference framework, eliminating the precision problems of direct visual assessment.
3Loss of time
If local malformed anatomy is used for positioning guidance, then no additional imaging is required, but the positioning is fundamentally flawed due to arthritic deformities
Solution Approach 1:
The patent extracts the positioning reference system from the local acetabular region and relocates it to the broader hemipelvis structure. By using landmarks distant from the diseased acetabulum (iliac spines, pubic tubercle), the system removes the influence of local pathological deformities while maintaining anatomical relevance. This extraction preserves reliability in malformed anatomy without requiring complex preoperative imaging.
Data Source
AI summary
An instrument for establishing orientation of a pelvic prosthesis comprises a hub, a first arm attached to and extending from the hub, and a second arm attached to and extending from the hub. The first and second arms define a nominal plane of the apparatus, and may extend from the hub at an angle relative to each other. Distances between the first and second legs and between the first and third legs are adjustable. The first, second, and third legs have tips, and the tips of the first, second, and third legs define a plane having a predefined geometric relationship to the nominal plane of the apparatus.