Bone Plate Locking Hole Structure to Prevent Screw Cross-Threading

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Solution Overview

Problem

Variable angle locking screws tend to cause cross-threading issues in bone plates, reducing the stability of the locked screw head due to improper fit between the internal and external threading.

Innovation Solution

A bone plate design with variable angle locking holes that accommodate both standard-type and variable-angle locking screws, featuring alternating threaded and recessed regions to prevent cross-threading, ensuring a secure form-fit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If variable angle locking screws are used to accommodate different screw orientations, then adaptability is improved, but cross-threading issues occur reducing stability

Engineering Contradiction:

Improveaccommodation of different screw orientationsVSAvoidstability of locked screw head

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The internal threading of the bone plate hole is segmented into multiple columns of thread segments arranged at different orientations. This segmentation allows the threaded head of variable angle locking screws to engage with multiple thread columns simultaneously, accommodating different screw orientations while preventing cross-threading through the distributed thread architecture

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bone plate hole features asymmetric internal threading with columns of thread segments positioned at different angular orientations rather than a single symmetric thread pattern. This asymmetric configuration enables the hole to accept screws at multiple angles while maintaining proper thread engagement and preventing cross-threading through the non-uniform thread distribution

Inventive Principle:

Principle #4Asymmetry

2Ease of manufacture

If standard threaded holes are used for locking screws, then manufacturing simplicity is maintained, but cross-threading occurs reducing fixation reliability

Engineering Contradiction:

Improvesimplicity of bone plate hole fabricationVSAvoidfixation stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The internal threading is divided into multiple discrete columns of thread segments rather than a continuous single-thread pattern. This segmentation can be achieved through specialized manufacturing processes while providing multiple engagement paths for screws, preventing cross-threading through the distributed thread architecture

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The manufacturing approach changes from creating a single standard thread pattern to creating multiple thread columns with specific geometric parameters. This parameter change enables accommodation of variable angle screws while maintaining manufacturability through controlled thread segment positioning and spacing

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3768181B2Bone plate with form-fitting variable-angle locking hole

Publication Date: 2026.02.11 DEPUY SYNTHES PROD INC

Figure 1A~1B
Figure 1C
Figure 2A~2B

AI summary

A bone plate (30) includes at least one variable angle locking hole (54) that is configured to threadedly mate with a variable angle locking screw (43) oriented so as to define any angle among a range of angles with respect to a central axis (45) of the VA locking hole at which a threaded head (59) of the locking screw is configured to threadedly purchase with the bone plate in the variable angle locking hole.