Inverse-Conical Guide Pin for Hip Socket Insert Guidance
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Solution Overview
Problem
The existing hip joint prostheses face challenges during the insertion of thin-walled metal shells into the pelvic bone, where deformation at the clamping cone occurs, leading to potential jamming and reduced durability due to tilting, especially under minimally invasive surgical conditions with limited visibility.
Innovation Solution
A hip joint prosthesis design featuring an inverse conical guide pin and guide bore, which provides precise guidance and support during insertion, maintaining high accuracy even in difficult conditions by ensuring a constant or increasing guide gap, thus preventing tilting and edge collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a cylindrical or conical guide pin is used for insertion guidance, then guidance is provided during insertion, but the guide length must be extremely small due to limited installation space, reducing guide accuracy when it is most needed
Solution Approach 1:
The guide pin is designed with an inverse conical shape where the diameter increases toward the insertion end rather than decreasing. This inversion allows the guide pin to achieve its maximum diameter at the insertion point, providing optimal guide accuracy precisely when needed during insertion, while still fitting within the limited installation space of the hip socket.
2Reliability
If a larger guide gap is realized to prevent tilting, then tilting is avoided, but guide accuracy decreases and the risk of socket insert tilting increases
Solution Approach 1:
By inverting the conical shape of the guide pin, the design achieves a constant or increasing guide gap during insertion rather than a decreasing one. This allows the guide gap to remain sufficiently large to prevent tilting while maintaining high guide accuracy through the inverse conical geometry, resolving the contradiction between reliability and manufacturing precision.
3Ease of operation
If conical clamping is used to connect socket insert and acetabulum, then self-centering guidance is achieved, but it only works with small initial tilting angles and fails with stronger tilts causing jamming
Solution Approach 1:
The inverse conical guide pin provides preliminary guidance action during the critical insertion phase before the conical clamping engagement is fully established. This preliminary guidance prevents initial tilting and ensures proper alignment, allowing the subsequent conical clamping to function effectively without encountering the limitation of small initial tilting angles.
Solution Approach 2:
The inverted conical shape of the guide pin complements the conical clamping geometry by providing guidance in the opposite sense, preventing tilting in the direction that would cause jamming. This creates a synergistic effect where the guide pin and conical clamping work together to provide reliable guidance under tilt conditions.
Data Source
Figure 1~2d
Figure 3a~4
Figure 5
AI summary
The invention relates to a hip joint prosthetic having a ball socket insert (3) and a hip ball socket (4), wherein a conical guide pin (5) is arranged on the pole (7) of the ball socket insert (3) and a guide bore (6) is arranged on the base of the hip ball socket (4) and the guide pin (5) is located in the guide bore (6) in the installed state of the ball socket insert (3) in the hip ball socket (4). In order to enable functional insertion of the ball socket insert in the hip ball socket at high guidance accuracy even under difficult conditions, according to the invention, the guide pin (5) is designed inverse-conically tapered, wherein the diameter of the guide pin (5) is less on the end turned toward the pole (7) than on the end (8) of the guide pin (5) turned away from the pole (7).