Acetabular Cup Positioning via Transverse Ligament Reference
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Solution Overview
Problem
Current methods for positioning an acetabular cup in hip replacement surgery are flawed due to inconsistencies in defining the orientation relative to the pelvis's anatomical planes and reliance on unreliable bony landmarks, leading to inaccurate reproduction of the natural joint's function.
Innovation Solution
A computer-aided surgery system that aligns the acetabular cup based on the transverse acetabular ligament and labrum, allowing for precise determination of the acetabular plane and selection of a matching cup template, providing visual guidance for surgeons to ensure accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methods use bony rim of acetabulum as alignment reference, then structural inlet plane can be identified, but the reference is unreliable due to disease deformation and does not define functional inlet plane
Solution Approach 1:
The patent introduces the transverse acetabular ligament as an intermediary reference structure that mediates between the bony anatomy and the functional requirements. The ligament serves as a reliable soft tissue landmark that is not deformed by disease processes affecting bone, and it directly defines the functional inlet plane of the acetabulum, resolving the contradiction between structural and functional alignment references
Solution Approach 2:
The patent replaces the mechanical/bony reference system (bony rim) with a soft tissue reference system (transverse acetabular ligament). This substitution allows for more reliable identification of the functional inlet plane, as the ligament maintains its anatomical position and relationship to the functional hip joint regardless of bony deformities
2Measurement precision
If abduction and version angles are defined relative to cardinal planes of pelvis, then orientation can be specified, but there is no clear definition of acetabular cup axis to define these angles
Solution Approach 1:
Instead of defining the acetabular cup axis first and then measuring angles from it, the patent inverts the approach by using the transverse acetabular ligament to directly define the functional inlet plane orientation. The ligament's anatomical position naturally provides the reference plane, eliminating the need for complex axis construction and providing straightforward angular measurements
3Adaptability or versatility
If global anatomical planes are used for alignment, then body-wide reference is established, but pelvis movement relative to body makes accurate positioning difficult or impossible
Solution Approach 1:
The patent segments the reference system from the global body coordinate system and creates a local reference system based on pelvic structures (transverse acetabular ligament). This segmentation allows the reference to move with the pelvis, maintaining accurate positioning even when the pelvis moves relative to the rest of the body, thus resolving the contradiction between having a body-wide reference and maintaining positioning accuracy
Data Source
AI summary
A computer aided surgery system, method, surgical method and instrument for guiding the positioning of an acetabular cup in a pelvis are described. The position of the transverse acetabular ligament of the pelvis and the position of the acetabular labrum of the pelvis are determined. The orientation of an acetabular plane including the acetabular labrum and the transverse acetabular ligament is calculated. A planned position for the acetabular cup is determined, in which an inlet plane of the cup is substantially parallel to the acetabular plane. The instrument comprises a mounting for attaching the instrument to a patient, a support, a guide defining a longitudinal axis, and for receiving a further instrument bearing the acetabular cup implant, and an adjustment mechanism. The adjustment mechanism can allow the angular orientation of the guide to be adjusted about at least two different axes to allow the inclination and version or anteversion of the longitudinal axis to be altered.