Joint Prosthesis Inner Screw Tool Holes
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Solution Overview
Problem
Existing joint prostheses with screw-like members have outer grooves that form sharp edges, which can cause tissue damage during screwing, as described in U.S. Pat. No. 5,147,386.
Innovation Solution
The joint prosthesis features inner holes in the screw-like members for a screw tool, allowing secure attachment without exposing the sharp outer grooves, as the holes are completely covered by the socket and head members when mounted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If outer grooves are provided in screw-like members for screw tool insertion, then screwing operation is enabled, but sharp edges are formed that can harm adjacent tissue
Solution Approach 1:
The patent applies nesting by placing the screw tool access hole inside the screw-like member rather than on the outer surface. The hole is positioned within the internal structure, nested among the threads and core, eliminating the need for external grooves that would create sharp edges. This allows the screwing operation to proceed through the internally located hole while the outer surface remains smooth and tissue-safe.
Solution Approach 2:
Instead of providing external grooves on the outer surface for screw tool access (conventional approach), the patent inverts the approach by providing the access hole internally within the screw-like member. This reversal of the conventional design eliminates the sharp edges that would otherwise be created by external grooves, while still enabling the screwing operation through the internal hole.
2Object-affected harmful factors
If inner holes are provided in screw-like members for screw tool insertion, then sharp edges are avoided, but the holes must be completely covered by socket and head members when mounted
Solution Approach 1:
The socket and head members are designed to nest over the screw-like members, with their outer surfaces completely covering the internally located screw tool access holes. This nesting arrangement ensures that the holes remain hidden within the assembled prosthesis structure, eliminating any potential exposure that could lead to tissue damage while maintaining the protective coverage.
Solution Approach 2:
The screw tool access function is extracted from the outer surface and relocated to the internal structure of the screw-like members. By removing the access holes from the external surface and placing them internally, the design eliminates the need for external grooves and ensures complete coverage by the socket and head members, thereby preventing tissue damage.
Data Source
AI summary
A joint prosthesis has two prosthesis members (2, 3) and each prosthesis member (2, 3) includes a first and a second screw-like member (4, 5) adapted to be screwed onto a respective bone (39, 41, 42). One prosthesis member (2) includes a member (6) having a socket and the other prosthesis member (3) a member (7) having a head. The socket member (6) has a mounting pin (22) insertable into a first hole (10) in the first screw-like member (4) and the head member (7) has a mounting pin (27) insertable into a first hole (11) in the second screw-like member (5). In the first as well as in the second screw-like member (4, 5) there is provided at least one inner second hole (30 and 33 respectively) designed to permit insertion thereinto of a rod (31) of a screw tool (32) in order to secure by screwing the first and second screw-like member (4, 5) respectively, at the respective bone (39, 41, 42). The second hole (30 and 33 respectively) is provided in a bottom (17 and 19 respectively) of the first hole (10 and 11 respectively).