Bone Screw Apertures for Porous Bone Stability
Solution Overview
Problem
Bone screws used in surgical applications face challenges in highly porous, osteopenic, or osteoporotic bone due to competing constraints between thread coarseness and bending strength, leading to frequent screw failure through loosening or breaking, despite enhancements like biologically favorable metals and surface texturing.
Innovation Solution
A bone screw design featuring a helically extending thread with a minor diameter and a major diameter, including apertures that allow bone ingrowth and accommodate changes in bone density, providing a structure for osteoconductive, osteoinductive, or osteogenic materials to enhance stability and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If larger (coarser) threads are used to improve mechanical purchase in porous bone, then thread engagement is improved, but bending strength is reduced
Solution Approach 1:
The patent applies porous metal material (such as titanium foam or trabecular metal) to the bone screw threads. This porous structure increases the surface area and allows bone ingrowth into the material, significantly improving mechanical purchase and thread engagement in porous bone without requiring larger thread dimensions, thereby maintaining bending strength.
2Ease of operation
If conventional bone screw design is used, then ease of insertion is maintained, but screw failure (loosening or breaking) is frequent
Solution Approach 1:
The patent combines conventional solid metal screw body (for structural integrity and ease of insertion) with porous metal thread portions (for bone ingrowth and stability). This composite structure allows the screw to be easily inserted like conventional screws while the porous threads provide enhanced stability and prevent loosening or breaking through biological fixation.
3Reliability
If thread form is optimized for mechanical purchase, then bone engagement is improved, but adaptability to bone remodeling is reduced
Solution Approach 1:
The patent employs porous metal material in the thread structure, which is a dynamic solution that adapts to bone remodeling over time. The porous structure allows bone to grow into and through the material, creating a living, evolving interface that maintains engagement as the bone remodels, unlike rigid conventional threads that cannot adapt to biological changes.
Data Source
AI summary
A bone screw includes a main body having a proximal end and a distal end. The main body extends along a longitudinal axis. The main body has an externally threaded surface that includes at least one helically extending thread having a minor diameter and a major diameter, which major diameter is greater than the minor diameter. The thread includes at least two flank surfaces extending between the minor diameter and the major diameter. The minor diameter of the thread defines a central portion of the main body. The thread may include at least one aperture that extends along an aperture axis through the thread between the flank surfaces.