Polyaxial Screw Locking Cap Thread Engagement

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current polyaxial screw systems for orthopedic surgery lack sufficient locking strength, compression, and fixed angle locking, which can lead to instability and complications during surgery.

Innovation Solution

A polyaxial screw system comprising a screw with a cylindrical shaft and a locking cap with an external helical thread, designed to engage the orthopedic component, providing superior locking strength and compression while allowing for flexible screw insertion angles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a polyaxial screw system is used to allow flexible insertion angles, then adaptability during surgery is improved, but locking strength and stability deteriorate

Engineering Contradiction:

Improveflexibility in screw insertion anglesVSAvoidlocking strength

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The screw system is divided into separate functional components: a polyaxial screw with spherical head for angular adjustment, a locking cap with external helical thread for securing, and an orthopedic component with internal helical thread for reception. This segmentation allows each component to optimize its specific function while maintaining overall system adaptability and strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The screw incorporates a spherical head that enables dynamic angular adjustment during insertion, allowing the screw to be inserted at variable angles relative to the orthopedic component. Once inserted, the locking cap provides fixed angular stabilization, creating a system that transitions from dynamic positioning to static locking.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If multiple interconnecting parts are used in polyaxial screw systems, then adaptability and adjustability are improved, but surgical time and procedure complexity increase

Engineering Contradiction:

Improveadjustability during surgeryVSAvoidtime to insert and secure screw

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The locking cap integrates multiple functions into a single component: it provides angular locking, secures the screw in place, and features an external helical thread that engages with the internal helical thread of the orthopedic component. This merging reduces the number of separate parts and simplifies the surgical procedure while maintaining adjustability during insertion.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If polyaxial screws are used instead of monoaxial screws, then precision in screw placement is improved, but stability and locking strength deteriorate

Engineering Contradiction:

Improveprecision in screw placementVSAvoidstability of screw fixation

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The spherical head of the polyaxial screw is designed to preliminarily engage with the internal concave base of the orthopedic component, establishing precise angular positioning before final locking. This preliminary engagement ensures accurate screw placement while the subsequent locking cap application provides stable fixed-angle securing.

Inventive Principle:

Principle #10Preliminary action

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 system achieves improved fixation and osteointegration of orthopedic components by providing enhanced locking strength, reduced component count, and simplified surgical procedures, thereby reducing the risk of screw misplacement and instability.

Implementation Method 1

The body of the locking cap comprises an external helical thread adapted to engage the internal helical thread of the hole of the orthopedic component

Methodology Applied

Scientific EffectHelical thread engagement: Screw

Implementation Method 2

The distal end of the locking cap may optionally define a substantially circular contact edge. The contact edge is adapted to impinge on the plurality of longitudinal crests on the head of the screw when the locking cap is inserted in the hole

Methodology Applied

Scientific EffectMechanical impingement: Mechanical Force

Data Source

PatentUS20250082369A1System for affixing an orthopedic component to a bone using a polyaxial screw

Publication Date: 2025.03.13 SKELETAL DYNAMICS INC

AI summary

Disclosed is a system suitable for affixing an orthopedic component to a bone using a polyaxial screw comprising an orthopedic component, a screw, and a locking cap; the orthopedic component having a hole with an entry side comprising an internal helical thread and an exit side comprising an internal concave base; the screw having a head comprising a convex base adapted to engage the concave base of the hole, and a convex crown having a plurality of splines; the locking cap comprising a proximal end having a cap socket, a distal end defining a substantially circular contact edge adapted to impinge on the plurality of splines on the crown of the screw when the locking cap is inserted in the hole, and a substantially cylindrical body therebetween having an external helical thread adapted to engage the internal helical thread of the hole.