Orthopedic Bone Fastener Hooked Thread Profile
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Solution Overview
Problem
Traditional bone screws used in spinal and trauma applications allow for micromotion and lateral separation, which can hinder healing and stability, as they fail to effectively resist axial and lateral forces.
Innovation Solution
The development of orthopedic bone fasteners with a hooked thread profile featuring undercuts and relief cuts, which provide improved bone purchase and resistance to axial and lateral forces, allowing for better stability and healing by securely lagging bone fragments together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional bone screw thread profiles are used, then the screw can be easily inserted into bone, but the screw allows micromotion and lateral separation, reducing stability and healing effectiveness
Solution Approach 1:
The thread profile employs asymmetric flank angles where the leading flank has a smaller angle than the following flank, creating a self-locking mechanism that prevents micromotion while maintaining ease of insertion. This asymmetric design ensures that once inserted, the screw resists lateral separation and maintains stable fixation without requiring complex additional structures.
2Device complexity
If traditional screw thread profiles are used, then the screw structure remains simple, but the screw fails to resist axial and lateral forces effectively
Solution Approach 1:
The invention modifies critical thread parameters including flank angles, thread depth, and pitch to optimize force resistance. By carefully selecting and varying these parameters along the thread length, the design achieves enhanced resistance to axial and lateral forces while maintaining relatively simple overall structure. The parameter optimization allows the thread to engage bone more effectively without requiring complex multi-component systems.
3Ease of operation
If traditional bone screws are used, then the surgical procedure remains straightforward, but the bone fragments are prone to lateral separation and micromotion
Solution Approach 1:
The thread profile is segmented into distinct functional zones: a leading flank for insertion, a root for bone engagement, and a following flank for force resistance. This segmentation allows each zone to perform its specific function optimally while maintaining overall simplicity. The segmented design enables the screw to lag bone fragments together effectively, preventing lateral separation without complicating the surgical procedure.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
Orthopedic bone fasteners, assemblies, and methods for spinal and trauma applications. The bone fastener may include a screw head and a shaft with an external thread helically wound around the shaft. Each thread section includes a crest, a root, and leading and following flanks connecting the crest to adjacent roots. The external thread may have a hook and latch style thread geometry. The leading and/or following flanks may define a hook, such as an undercut, configured to improve bone purchase, resist axial and lateral forces, improve pull-out strength, minimize micromotion, and/or lag bone fragments together.