Bone Fixation Device Transverse Locking Mechanism

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Solution Overview

Problem

Current bone fixation devices for femoral fractures lack effective mechanisms to securely lock and stabilize the femoral head relative to the remainder of the femur, which can hinder proper bone healing.

Innovation Solution

A bone fixation device comprising a nail with a transverse bore and a screw assembly, where the screw is locked against movement and rotation using a locking device with complementary patterns, such as wave-like knurled surfaces or splines, to ensure stable fixation of the fractured bone fragment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple screw locking mechanism is used, then the device complexity is reduced, but the reliability of bone fragment stabilization deteriorates

Engineering Contradiction:

Improvelocking mechanism complexityVSAvoidbone fragment stabilization

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The locking mechanism is divided into multiple functional segments: a locking device with clamping surfaces, a screw assembly with engagement surfaces, and complementary patterns (knurled surfaces, splines, or flats) that interlock. This segmentation allows each component to perform its specific function while collectively providing reliable stabilization without excessive complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The locking device and screw assembly feature asymmetric complementary patterns such as knurled surfaces, splines, or flats that mate together. These asymmetric features prevent relative rotation and movement in specific directions while allowing controlled engagement, thereby enhancing stabilization reliability without requiring a completely complex locking system.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If a locking device with complementary patterns is used, then the stabilization reliability is improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvescrew assembly lockingVSAvoidpattern alignment precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The complementary patterns (knurled surfaces, splines, or flats) serve multiple functions simultaneously: they provide friction resistance, prevent rotation, guide alignment during assembly, and distribute locking forces. This multi-functionality reduces the need for extremely precise manufacturing of individual features while maintaining overall locking reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The complementary patterns are pre-formed on the screw assembly and locking device surfaces before final assembly. These pre-formed features (knurled surfaces, splines, or flats) automatically align and guide the components into their correct relative positions during assembly, reducing the need for high-precision alignment operations and lowering manufacturing precision requirements.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9895177B2Bone fixation device for treatment of femoral fractures

Publication Date: 2018.02.20 ARTHREX GMBH

AI summary

A bone fixation device according to an exemplary aspect of the present disclosure includes a nail extending along a longitudinal axis. The nail is provided with a transverse bore arranged along a transverse axis that intersects the longitudinal axis. The bone fixation device further includes a screw assembly received in the transverse bore, and a locking device. The locking device is configured to clasp the screw assembly to lock the screw assembly against movement along the transverse axis and against rotation about the transverse axis.