Endosseous Screw Barrel Profile for Angular Extraction
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Solution Overview
Problem
Existing orthopedic devices with endosseous screws face difficulties in removing screws from bone sites after osteosynthesis, particularly with angular stability plates, due to the lack of effective extraction means, leading to complications and potential impossibility of screw removal.
Innovation Solution
The design of endosseous screws with a screw head featuring a barrel-shaped external peripheral profile allows engagement with a tubular manipulating wrench, enabling easy extraction even at angles, and includes a longitudinal stem for insertion and optional annular weakening groove for separation, facilitating torque transmission and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a recessed hexagonal cavity is used for screw insertion and tightening, then the screw can be securely fastened to the plate during osteosynthesis, but the screw becomes difficult or impossible to remove after osteosynthesis due to cavity occlusion or deformation
Solution Approach 1:
The screw head is divided into two functional zones: an internal recessed hexagonal cavity for tightening during osteosynthesis, and an external barrel-shaped peripheral profile for removal after osteosynthesis. This segmentation allows each zone to serve its specific function independently, resolving the contradiction between secure fastening and easy removal.
Solution Approach 2:
Instead of providing only an internal cavity for tool engagement, the invention adds an external engagement profile that protrudes from the screw head. This external profile allows the wrench to engage the screw from the outside, enabling removal even when the internal cavity is occluded or deformed, thus inverting the traditional approach of relying solely on internal cavities.
2Device complexity
If shaft screws are used without extraction means, then the screw structure is simple and strong, but the screw cannot be removed after osteosynthesis
Solution Approach 1:
The screw head is segmented into a simple shaft portion and an engagement portion with external facets. This minimal segmentation adds only the necessary external profile for removal while keeping the overall screw structure simple and maintaining structural strength, resolving the contradiction between simplicity and removability.
3Adaptability or versatility
If a recessed hexagonal cavity is used, then instruments with suitably shaped heads can untighten screws even without perfect alignment, but the cavity is often occluded or deformed during osteosynthesis or surgical removal
Solution Approach 1:
The external barrel-shaped profile acts as an intermediary engagement interface between the wrench and the screw. Instead of relying directly on the internal cavity that may be occluded or deformed, the external profile provides an alternative pathway for torque transmission, ensuring reliable removal even when the original engagement path is blocked.
Data Source
AI summary
Endosseous screw (1) for fixing a plate (102) to a bone site (300), comprising an at least partially threaded shaft (2), insertion means for inserting the screw into a bone site and a distal portion (33) provided for engaging said plate to fasten it to said bone site and comprising a head (3) having facets (30) defining an external peripheral profile provided for engagement with a tubular manipulating wrench, to allow the screw (1) to be extracted from the bone site (300) into which it has been inserted, wherein the facets (30) are curvilinear and the external peripheral profile defined by same facets (30) has a convex barrel-like shape, in order to allow a stable coupling between the tubular manipulating wrench and said profile, which is maintained during the untightening phase of screw from plate, even when said tubular manipulating wrench is oriented in an inclined direction with respect to a longitudinal axis (x) of the endosseous screw (1).