Acetabular Cup Alignment via Center Axis Calculation
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Solution Overview
Problem
Current methods for orienting the acetabular prosthetic cup during total hip arthroplasty, relying on the anterior pelvic plane, often result in inaccurate placement due to variations in patient anatomy and pelvic position, especially when the patient is moved from a supine to a lateral decubitus position, leading to increased operative time and potential sterility issues.
Innovation Solution
Determining the acetabulum center axis by selecting and averaging three rim points around the acetabulum, calculating geometric points to define a line indicative of the acetabulum center axis, and using a computer-aided navigation system to align the acetabular prosthetic cup relative to this axis, independent of the anterior pelvic plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the anterior pelvic plane (APP) is used to orient the acetabular prosthetic cup, then the orientation can be established, but significant errors occur in cup placement due to anatomical variations and pelvic position changes
Solution Approach 1:
The invention extracts the cup orientation determination from dependence on the anterior pelvic plane (APP) and establishes it independently through the acetabulum center axis. By selecting rim points directly on the acetabulum and computing geometric points (D and E) that define the center axis, the method removes the unreliable APP reference, thereby improving both measurement precision and reliability of cup placement
Solution Approach 2:
The invention introduces the acetabulum center axis as an intermediary reference between the anatomical landmarks (rim points) and the cup orientation. The computed geometric points D and E serve as mediators that translate irregular rim point measurements into a reliable central axis, which then guides accurate cup placement without being affected by APP variations
2Ease of operation
If the patient is moved from supine to lateral decubitus position, then surgery can proceed, but the accuracy of anterior pelvic plane identification is diminished
Solution Approach 1:
The invention segments the cup orientation determination into two independent components: (1) selecting rim points on the acetabulum to define its geometry, and (2) computing the center axis from these points. This segmentation allows the procedure to be performed independently of patient position, as rim points can be accurately identified in lateral decubitus position without relying on APP landmarks that become difficult to locate
3Measurement precision
If the anterior pelvic plane (APP) is acquired in the supine position prior to turning the patient, then orientation data is obtained, but operative time is increased and sterility may be compromised
Solution Approach 1:
The invention performs the essential measurement action directly in the surgical position (lateral decubitus) rather than requiring preliminary measurements in supine position. By selecting rim points and computing the center axis in one continuous process during the actual surgery, the method eliminates the need for pre-positioning measurements, thereby reducing operative time while maintaining measurement precision
Solution Approach 2:
The acetabulum itself provides the reference information needed for orientation through its own rim points and geometry. The rim points on the acetabulum serve as self-contained landmarks that define the center axis, eliminating the need for external APP references that require separate identification procedures and increase operative time
Data Source
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AI summary
An apparatus and method is disclosed for aligning the anteversion and the inclination of an acetabular prosthetic cup within an acetabulum of a patient. The apparatus and method comprises calculating the orientation of acetabulum center axis. The acetabular prosthetic cup is aligned relative to the calculated acetabulum center axis. The acetabulum center axis is calculated from selecting rim points located about the acetabulum of the patient.