Self-Drilling Osteosynthesis Screw with Segmented Cutting Threads
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Solution Overview
Problem
Existing osteosynthesis screws for orthopedic surgery face challenges such as the need for pre-drilling, weakness due to cutting ridges, and difficulty in achieving both good penetration and anchorage without compromising bone integrity, especially in thin cortical bones.
Innovation Solution
A self-drilling and self-tapping screw with a tubular or non-tubular design featuring three portions: a distal conical portion with threads, a smooth central barrel, and a proximal conical portion with threads, where the distal end is conical and has multiple cutting ridges formed by material removal, allowing for conical penetration and compression without pre-drilling, and providing strong anchorage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional self-tapping screws are used with cutting ridges defined at the bore, then self-tapping capability is achieved, but the screw becomes weak and teeth break easily
Solution Approach 1:
The screw thread is segmented into two distinct functional zones: a first thread portion with cutting ridges for self-tapping, and a second thread portion without cutting ridges for strong bone anchorage. This segmentation allows each zone to optimize its specific function without compromising the other.
Solution Approach 2:
Different portions of the screw have different local qualities: the first thread portion has cutting ridges for penetration, while the second thread portion has continuous material for strength. This local differentiation resolves the contradiction between self-tapping capability and screw strength.
2Strength
If screw length is increased to ensure good anchorage, then anchorage is improved, but the screw creates discomfort and must be screwed immediately in contact with bone without pushing it away
Solution Approach 1:
The distal end of the screw has a conical portion with a specific angle that creates localized compression of the bone at the insertion site. This localized action provides strong anchorage without requiring excessive screw length that would cause discomfort.
Solution Approach 2:
The conical distal end provides a curved insertion geometry that allows the screw to be introduced at an angle, creating compression forces that secure the bone without requiring the screw to be pushed all the way to the distal end, thus avoiding discomfort.
3Ease of operation
If cylindrical end is used for good penetration, then penetration is improved, but anchorage is compromised
Solution Approach 1:
The screw is segmented into a distal conical portion for penetration and a proximal cylindrical portion for anchorage. This segmentation allows the distal end to be conical for easy penetration while the proximal portion maintains cylindrical geometry for strong bone anchorage.
Solution Approach 2:
The screw exhibits asymmetry in its geometry: the distal end is conical while the proximal portion is cylindrical. This asymmetric design optimizes both penetration (at the conical distal end) and anchorage (at the cylindrical proximal portion) without compromising either function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The screw achieves immediate penetration and anchorage in bone, ensuring stability and compression without passing through the bone, enhancing consolidation and reducing postoperative discomfort and pain.
Implementation Method 1
the attack portion, that is to say the most distal of each thread, has a plurality of cutting ridges (AR) obtained by removal of material
Implementation Method 2
the distal portion having an external diameter that is slightly smaller than that of the proximal portion, making it possible to place in compression the two bony portions to be fused together
Implementation Method 3
a proximal portion or head comprising threads (A2), the distal portion having an external diameter that is slightly smaller than that of the proximal portion
Data Source
AI summary
The invention relates to a self-tapping and self-boring osteosynthesis screw for compressive orthopaedic surgery, characterised in that, in the bone engagement regions, at both the distal portion (A1a) and at the proximal portion (A2a), the sum of the angles defining the outer taper of the shank (f) and the taper of the crest line of the screw thread pitch (P) is higher than 45°, and in that the leading portion (i.e. the most distal one) of each thread includes a plurality of cutting edges (AR) obtained by stock removal.