Polyaxial Bone Fixation Element In-Situ Assembly

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Solution Overview

Problem

Existing spinal fixation systems lack simplicity and flexibility in securely mounting spinal rods to vertebrae, particularly in polyaxial rotation, which complicates surgical procedures and access during spinal stabilization and fusion.

Innovation Solution

A polyaxial bone fixation element comprising a bone anchor, a collet, and a body with a rod-receiving channel, allowing in-situ assembly where the bone anchor is secured to the vertebra before being received within the body, enabling easy implantation and secure mounting of the spinal rod with polyaxial rotation capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the bone anchor is pre-assembled with the body and collet, then the structural integrity is maintained, but the surgical visibility and access around the anchoring site are reduced

Engineering Contradiction:

Improvestructural integrityVSAvoidsurgical visibility and access

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The fixation element is divided into separate components (bone anchor, body, and collet) that can be implanted independently. The bone anchor is first secured to the vertebra, then the body and collet are attached subsequently, allowing surgeons to access and visualize the anchoring site without obstruction from pre-assembled components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bone anchor is implanted and secured to the vertebra before the body and collet are attached. This preliminary action allows the critical anchoring step to be performed with maximum surgical access and visibility, while subsequent assembly steps occur after the anchor is firmly in place.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If the pedicle screw body is rigid and fixed, then the mounting precision is high, but the flexibility in positioning and polyaxial rotation is reduced

Engineering Contradiction:

Improvemounting precisionVSAvoidflexibility in positioning

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The system transitions from a rigid fixed structure to a dynamic assembly where the collet can move axially within the body and the bone anchor can rotate polyaxially relative to the rod-receiving channel. This dynamic design allows the bone anchor to be positioned at various angles (polyaxial rotation) while the locking mechanism maintains precise positioning once secured.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The collet is nested within the body, and the bone anchor head is received within the collet. This nested configuration allows the smaller collet to move independently within the larger body, providing flexibility for polyaxial positioning while maintaining precise control through the locking cap mechanism.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Strength

If the spinal rod is securely clamped to the bone anchor, then the fixation strength is high, but the ease of implantation and adjustment is reduced

Engineering Contradiction:

Improvefixation strengthVSAvoidease of implantation

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The traditional complex mechanical locking system is replaced with a simplified cam-actuated locking mechanism. The locking cap, when rotated, uses cam surfaces to automatically clamp the spinal rod against the bone anchor through the collet, providing strong fixation with a simple rotational motion that is easy to perform during surgery.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The locking mechanism is designed to automatically engage and clamp the spinal rod when the locking cap is rotated. The cam surfaces and collet geometry cause the clamping action to occur automatically as part of the locking process, eliminating the need for separate clamping steps and simplifying the implantation procedure.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11998246B2Polyaxial bone fixation element

Publication Date: 2024.06.04 DEPUY SYNTHES PROD INC

AI summary

The present disclosure includes a polyaxial bone fixation element for use in spinal fixation to interconnect a longitudinal spinal rod with a patient's vertebra. The polyaxial bone fixation element preferably includes a bone anchor, a collet, a body, and a locking cap. The polyaxial bone fixation element preferably enables in-situ assembly. That is, the polyaxial bone fixation element is preferably configured so that in use, the bone anchor may be secured to the patient's vertebra prior to being received within the body. Accordingly, the polyaxial bone fixation element enables a surgeon to implant the bone anchor without the body to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the body can be snapped-onto the bone anchor. The bone anchor preferably also includes a second tool interface so that a surgical instrument can be directly coupled to the bone anchor.